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repower for 1969 46 MY

Discussion in 'Chris Craft Roamer Yacht' started by q240z, Dec 18, 2007.

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  1. q240z

    q240z New Member

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    The story on my new 46 Roamer was that it originally came with 8v71 power, which got swapped out to twin turbo and intercooled 543ci SeaMaster gassers. The more I look at this thing, though, the more I'm convinced it was originally a 427 gasser. The fuel tank doesn't have a return line or even a port where there might have previously been a return line. That almost certainly means it wasn't a diesel.

    Then there's some paperwork I found that indicates 427 power. It's not the original build sheet so from a provenance standpoint isn't especially reliable. BUT, taken along side the fuel tanks I'd say it supports the theory that this boat has always moved with gas power.

    The deal is, I've been thinking repowering "back" to diesel ever since we found this rig. Just yesterday, a local boatyard owner called me to report that he had a pair of 6-71TIBs w/gears for $2500. As you would imagine, one of the engines needs a cylinder head and cylinder kit on one jug. The other engine needs oil/fuel coolers. I can't imagine getting 930hp for any less.

    The old SeaMasters will come out over the next two weeks, along with a bunch of other junk. I haven't decided for sure about the TIBs, but any thoughts on the matter would be appreciated.

    Cheers,

    Q
  2. 9lives

    9lives Member

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    repower on a 46

    Q

    My 41' Regal was originally designed as a diesel build but when it left the factory it had 427's. The tell tale evidence was beefed up engine stringers, monel fuel tanks, and side vents in the stern that other gas engine boats didn't have.
    You should see if Jim Wick from LPX has any data on your hull or try the museum for the hull card and other info.

    Mark
  3. chriswufgator

    chriswufgator Member

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    Get the diesels....diesels....diesels....diesels....

    As to the original power, I believe 46' is pretty big to have come with 427s from the factory. I think yours would be the only 46' Roamer I have ever seen with original gas power. To my knowledge, anything over 44' or so in length came with diesels, gas wasn't even an option. I can ask my mechanic for you, if you want. He was Chris-Craft factory trained back in the 60s so he would probably know better than me.

    Or, like someone else suggested, contact the mariners museum and get your original build specs.

    Also, you can't be sure of the original configuration just from the fuel tanks. It's a 40 year-old boat, and those tanks have probably been replaced at least once by this point. That doesn't mean much by itself.
  4. q240z

    q240z New Member

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    Well, this isn't the first large Chris yacht I've owned so this stuff isn't a complete and total stab in the dark for me. These are without a doubt the original tanks. The fuel tanks were obviously not steel or aluminum but I didn't have the acid kit to test the material last time I was on the boat. Then Mark came along and mentioned monel and the lights went on.

    The fuel lines are original and are sized for gas, not Detroit Diesels. Like I said, there were no return lines, which screams gas. The list kinda just goes on. The fella in Alex VA (Eric? Alloyed2sea?) provides specs for each model and 427 was listed as one of two possible power options in these 46s. The final bit that has me convinced is that Jim Wick wrote back and said the HIN comes back as a 1969 46 footer with 427 Ford pahwah.

    So, the info I got from the guy who's selling the boat saying that this beast had 671Ns originally was urban legend at its best.

    On the upside, a guy called me today who is interested in the twin turbo SeaMasters. Hopefully he'll show up with a trailer when the crane yanks 'em out next Thursday. If not, it's ebay or the scrap metal yard. There must be 20 pounds of copper in each of the exhaust risers alone.
  5. SeaEric

    SeaEric YF Historian

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    The 671 tib's must be toast for that money. For the cost to rebuild them you could explore many other options. Keep horsepower to weight ratio in mind. If cost is a huge issue, go back with gas. You must remember that diesels may require a change in shaft diameter, props, exhaust tube diameter, raw water intake diameter. All very expensive retrofits. There could be some reasonably priced, albeit lower HP diesel options that may be workable with the present plumbing. Look at B series Cummins, or 3208 Cats as possibilities. My .02 worth!
  6. q240z

    q240z New Member

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    The boatyard owner who has the TIBs is a buddy of a buddy and we've met before. He kept them after repowering the boat they came out of rather than selling them off as cores or scrap because, he claims, one only needs a head and a cylinder kit (rings, actually, which he claims look like Chiklets, but if you're already in there...), and the other engine needs fuel & oil coolers and other bolt-ons. The guy's not an idiot, so I can't imagine that he would have kept junk motors on spec. I haven't seen them in person yet, but the guy's trustworthy. Which is not to say that I'm definitely going that way, but hopefully explains why I'd even consider them.

    The shafts look to be 2", which are well within the range for the way I will use the boat. Boatdiesel's calculator says 2.31" is recommended for 465hp, but that's with a safety factor of 2. Since I would derate the engines to match the cruising we do 99.9% of the time, there's no reason to go with rated shafts.

    There are two sets of props (3 & 4 blade, the latter is 24x24) but for my purposes I'd need larger ones anyway. Something between 28 and 30" is what I'm considering. The exhaust looks to be 6" right now, which also appears to fall within specs.

    But the raw water intake is on the wrong end of the engine and might be too small. Then again, I was on a 60 Roamer w/12-71TIs and was startled at how small the seacocks, strainers, and raw water plumbing was--like, 2" or so. That's smaller than what's on my current 52' Connie w671s! I'll already have a welder in for a day to do engine mounts, block off a few old transducers, and zip up some pits. In the grand scheme of things I doubt the cost of relocating and installing new raw water plumbing will be that much.

    There are a few issues that pretty much kill the idea of keeping it gas: E10 and soon to be E15 & E20's got a shelf life that's less than milk. Equipment durability. Increasing risks w/CO &/or sparky boom-boom. Webasto diesel hydronic heaters don't burn gas... The list just kinda goes on.

    Plus, I like the sound of 6-71s. VROOM! :)
  7. q240z

    q240z New Member

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    OK, we're back to powerplants again. It turns out that the shafts are actually 1.5" and the exhaust is 4"ID. That means that the max HP that can be run on this boat without $ignificant upgrade$ is about 350 or so.

    Here's the line-up:
    New 300hp Nanni (Toyota) diesels are $40,000 (engines, gears, mounts, wiring & panels)
    New 200hp Nanni (Toyota) diesels are $30,000 (engines, gears, mounts, wiring & panels)
    New/factory reman 300-330hp Cummins are $25,000 (engines, gears, mounts, wiring & panels)
    Used 300-330hp Cummins are $20,000 (engines, gears, mounts, wiring & panels)
    New/factory reman 210hp Cummins are $20,000 (engines, gears, mounts, wiring & panels)
    New/factory reman 160hp Cummins are $17,000 (engines, gears, mounts, wiring & panels)
    475hp (derated and governed to 300hp) 671TIBs w/gears needing cylinder kits + ??? are $2500

    And--don't laugh, I'm looking at every option and keeping in mind that we rarely cruise faster than 10kts in our current vessel--zero hour 90hp Ford Lehmans w/gears for $3,500 for the set.

    Buc book says the Retail Price Range for these boats is $86,800-$95,400, which puts the 300hp Cummins & Nanni options into perspective. I'm looking at the price of diesel, the speed we tend to travel at almost all of the time, the cost of the repower, and ongoing operating expenses and trying to figure out why the Lehmans are the wrong way to go. I mean, 1.5GPH @ 7kts is what many folks claim out of the 90HP Lehmans in single-engine "fast trawler" applications (i.e. same basic hull form as the Roamer but without the drop dead sexy lines up top). Between 4,000 and 10,000 hours is not uncommon with unstressed Lehmans. And according to some calculators at boatdiesel, 180HP total onboard would yield a comfortable cruise of 7-8kts and a max speed of 11. What's not to like?

    Or, put another way--what is it about new Cummins or Nanni that would justify 10x the price of the Lehmans if we're pretty much always putzing around at 7-11kts anyway?
  8. SeaEric

    SeaEric YF Historian

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    Repowering to diesel and then running her like a trawler for economy is one thing. Making her a trawler forever with a tiny pair of Lehmans is quite another. If you think you will be happy with that, and you plan on being buried at sea in this boat, then go for it. With that power, if you ever wanted to sell her, your prospects would be quite limited.

    If you cruise slow anyway, go back with 454's and run them at 1800 RPM's. They will last forever and your retrofit will be simple. If you intend to stay on the Bay, this is what I would do.

    Or, if you're island bound- shop for a 250 to 300ish HP pair of good running take out diesels or go for the remans. A friend of mine sold a perfectly good pair of Cat 3116's with 400 hours for $14,000.

    I do think that with almost any diesel, except the Lehmans, the 1 1/2" shafts will need to be beefier.
  9. Seafarer

    Seafarer Senior Member

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    It seems to me a lot of the discussion of hull speed vs. cruising speed vs. efficiency comes from experience with displacement hulls and not with planing hulls.

    q240z, what is your experience with planing hulls? if you under power a planing hull to hit a certain set displacement hull's cruise speed, you will have an inefficient and ill-handling pig of a boat. you will use the same fuel to get a far shorter distance (gph vs. gpm or mpg) than going with a higher power and getting the boat up on plane with a 1600-1800 rpm cruise with a larger diesel.

    our old huckins was 1.21 mpg with 8v71 naturally aspirated (supercharged) 318's running 17kt @ 1800rpm with a planing speed of about 11 kt (approx 16gph, or 8gph per engine, for 20mph). cutting it back to the 10kt hull speed dropped economy to about .9 mpg because it was constantly trying to climb out of its own hole. when the boat still had the 250HP Cummins NH engines, it was approx. 1 mpg for a 14.6 kt cruise.

    you can not estimate fuel consumption and cruising speed the same way with a planing hull as with a displacement hull! you will end up burning far more fuel than you expect and have an incredibly unpleasant ride to go along with poor maneuverability in a seaway by underpowering or overloading a planing hull.
  10. q240z

    q240z New Member

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    "perfectly good pair of Cat 3116's "

    HA! Now there's a contradiction in terms if ever I saw one! lol

    Seriously, I've also talked with somebody who runs 370hp Cummins in their boat with 1.5" shafts. As far as the shafts go, I've always heard that materials may be just as important as diameter. It would be interesting to see what these shafts are made of.

    The biggest problem I see with any kind of gas powered cruiser is that e10 seems to have an incredibly short shelf life. e15 will be shorter and e20, when it gets here, will be shorter still. I don't see gas as a viable option for this and several other reasons.

    Seafarer, my experience is primarily with semi-displacement hulls. But having corresponded with a couple of 46 Roamer owners, it appears as if calling these big yachts planing hulls is a tad over-optimistic. As far as the ill-handling planing boat at displacement speeds theory goes, I think there's an awful lot of misinformation and urban myth out there. When we putz along at 8kts in our Connie, things are more or less dead flat. The notion of handling doesn't really apply. When in nasty weather, we do what my old man always taught me to do--keep it slow. Now, if we were running at the speeds you're talking about (i.e. in that nasty region where you're way above displacement speed but nowhere near planing), the story probably changes. Personally, I've never been in the habit of running at those speeds.

    There is a fellow on a Hatteras forum who, with 12v71TIs in a 61-footer, manages up to 3nmpg by running his vessel at the speed he has modified it to run at best--around 9kts. Running that semi-displacement boat at WOT, he manages somewhere around 0.5mpg. This is not unlike what I have experienced in my 52 Connie. I have a hard time believing that 16-ton Roamers pop up on plane so well that they would not achieve maximum efficiency at true displacement speed rather than the maximum hole-diggin' speeds you give as examples.

    Unfortunately, this Lehman idea won't go any further. These engines, I've learned, are pre-Lehman Fords. They are apparently much smaller blocks than the Lehmans were. The search continues...

    It would be helpful, though, if some other 46 Roamer owners would chime in with their shaft, exhaust, and HP numbers. From what I've heard so far from them, none of them approach 3nmpg while mashing the "loud sticks" forward.

    I'm curious, Seafarer--what are "8v71 naturally aspirated 318's"?

    Cheers,
  11. Seafarer

    Seafarer Senior Member

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    Detroit (or at the age of the engines in our old Huckins, General Motors) Diesels were considered NA engines if they weren't turbocharged. So an 8V71NA 318 is a supercharged V8 turning 318 HP - king of the hill in its day, but a far cry from the more modern engines you've got a line on.

    Background: My grandfather repowered the boat to those Detroits in the early 1960's. They were still running the boat this past season and, though apparently they had a major rebuild a few years ago (past due when we sold her), we only ever had to do top end rebuilds in the nearly 25 years we had the boat with them. Stone-simple and about as reliable. They leak oil, they burn oil, they make noise. And they seem to always run.

    As for the handling thoughts, mine are based solely experience with true planing hulls - 20' up to 64'. To the best of my knowledge, at WOT the Si-Go would turn just a tick over 20kt. and fuel economy dropped pretty substantially. By the time we put her up for sale, she'd probably not seen WOT in 15 years, so I don't know hard numbers for speed or "economy" there. That boat, however, would squat, wallow, and require constant steering correction at 8-10kt. - and she got thirsty. As an added bonus, being only a 3'6" draft to the bottom of the props on a 65' boat, she also had a tendency to let even a light wind push her well off course given a little inattention at the helm. Put her up on plane at 11, and it was a whole different boat, right up to cruising speed. Straight as an arrow, in anything up to moderate seas.

    I'll definitely agree with what your old man taught you about bad weather, as my grandfather and father imparted the same wisdom on me.

    And, lastly, the Hattie owners I've known have all agreed with what the fellow on the other forum says - 9-10kts with big engines returns excellent economy.

    Cheers.
  12. q240z

    q240z New Member

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    Gotcha. I've always heard of that version of the 871s as 320hp.

    Without input from owners of sister ships to this one, it's difficult to say when the boats begin to plane. Again, with my 52 Connie (a narrower and longer boat) the ride is very pleasant at hull speed.

    The beauty of the particular Hattie guy's experience that I mentioned was that he went to bigger wheels with more pitch and derated his governor to WOT at 1600rpm. THEN, he put pyrometers and pressure gauges to the engines to see exactly what improvements happened. The proof's in the results even if it's counterintuitive to folks who believe that the engines in nondisplacement hulls must be pushed to 200 ticks off WOT--slow speed running coupled with proper loading at the prop yields very happy older, heavier engines and fabulous economy.

    Little of this helps for my boat, though, because the wimpy 1.5" shafts I've got (assuming they're 304SS) can take no more than about 160 slow-turning diesel hp. High revving diesels like Nanni or Yanmar are good for up to 300hp, but who cares since we normally putz along at hull speed? Hence the interest in low output Lehmans, particularly since this is the last boat I ever intend to outfit.
  13. acellist

    acellist Member

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    Planing, exhaust and shaft size for 46' Roamer Riviera

    Our 8V 71N Detroit Diesels are rated at 320 hp in the original manuals from Detroit that came with our Roamer.
    The shafts are 1.5 inches in diameter.
    Wheels are four blade 28X28s.
    The exhausts at the stern are 6 inches OD about 5.75 inches ID.
    We took her up to her maximum rpm (2100) and achieved 20.5 mph.
    That is 2.5 mph below Chris Craft's 1969 rating (1968 was an estimate at 27 mph) over-sized 4 blade props are probably the culprit.
    The bow started to rise around 1800 rpm c 17 mph.
    As I lowered the trim tabs on the way up to 2100 rpm the bow dropped somewhat, but not to a completely level attitude.
    There are few places around Pittsburgh where you may even think about performing such a feat.
    The two photos below were taken in one such place on the Monongahela River.
    Our wake was still a bit deep for true planing in my estimation.
    She was rooted and very stable at that speed.
    I do not know if she would have "planed" or gained more speed if I had raised the trim tabs when she stabilized, since we ran out of wilderness after 3 miles, what do you think.
    At best it remains an experiment for the Spring season.

    Attached Files:

  14. Seafarer

    Seafarer Senior Member

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    It may well be that they were rated for 320, and the fact that they also powered the trucks in my grandfather's business as 318's is why he called them that? That's what he referred to them as, and that's what i grew up calling them. 318hp, 866lb/ft. - it's entirely probable that he was quoted on-road specs.

    acellist seems to have much more relevant information for this discussion, though!
  15. q240z

    q240z New Member

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    acellist, thanks for the numbers. I love the shot out the transom window.

    1.5" shafts with 871s? Hmmm...that leads me to believe that the shafts are not made of 304 stainless. Your exhaust sizing tells me that these boats were purpose-built for the power they originally came with. A sister ship to mine (ie 427 gas-powered) also came with the 4"ID pipes. So, given that I'm not interested in refitting shafts or exhaust on this boat, the limiting factor to the max HP I can install is the exhaust (assuming gas boats came with shafts of the same material as diesel boats).

    OK, so with 640hp on tap you can and do thunder down the river at 20.5mph. Tell us, what speed to you tend to travel at and why? Also, at 10kts or so does your boat handle like a pig?

    Cheers,
  16. acellist

    acellist Member

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    That shot out the transom certainly made things clearer to me and in answer to your questions q240z, we traveled the 2250 miles of our trek from Harrison Twp, MI on Lake Saint Clair through Lakes Huron, Michigan and the inland river system from Chicago to Pittsburgh aiming to average 100 miles a day. It took us 25 days to make Pittsburgh. Fortunately, although I was making allowances for waiting time at locks, there were only two long periods (more than 15-20 minutes) spent sitting at idle. One was Brandon Road Lock on the Illinois River System (3 hours) and the other was a few days up the Ohio where we waited an hour and a half or two. (That’s pretty efficient river traffic handling, 32 locks and only 2 extended waits.)

    If anyone wants to see them there are 79 out of the 6159 pictures Kim took on our ride at: http://outdoors.webshots.com/album/560759815Ntalud

    As to what speeds I tend to favor, I had been told by a reliable source prior to departure from the Detroit area that diesel engines like to run at two-thirds of their maximum rpm and pretty much kept to 1400 rpm throughout the journey which produced c10.5 mph on the GPS. We left every day about 7:00 AM and arrived at each next stop around dusk. Occasionally, when port arrivals demanded, we would push up to around 1500 to 1600 rpm and produce c12.5 mph. That’s all subject to slowing to no wake speeds when passing marinas, cities, and partying boaters pulled up on beaches along the way. These rivers were sparsely peopled for the most part.
    You asked about handling. Frankly, I was delighted at her performance at any speed (the port engine is idled a little slow and tended to cut out when pulled all the way back.)
    South of Peoria I gave my wife and two crew members a respite and towed them in two turns on a two man inflatable triangular raft, positioning the tow rope to hold them atop the front edge of the third roller in the middle of the wake at 10.5 mph. During those rides I performed two 360s, one to port and one to starboard. Far more stable than our previous Bayliner 2855 Ciera with the 7.5 liter Mercruiser outdrive.
    She handles like a charm when making small detailed maneuvers docking at idle speeds. I manage docking by approaching at 900 rpm or so and going into neutral about one to two boat lengths away, executing landing at idle speed using only the gear shifts with the rudders angled away from the dock side. Having those big four blade props helps greatly in controlling motion and drift at those idle speed maneuvers. I can honestly say that she responds to the touch and handles with ease in every situation I’ve come across, including backing down immediately from two sudden and harrowing encounters.
    Out the eight cruisers I’ve owned, she’s my favorite without any doubt!
    Stay well everybody, and have a great new year,
    acellist

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  17. q240z

    q240z New Member

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    Excellent write-up, acellist. If I recall, you averaged just about 1nmpg on that trip.

    Funny thing about the 90hp set of Lehmans...they burn about 1gph while producing sufficient power to theoretically push this boat along at about 8-9kts. That's about 4x the fuel economy of your average Hatteras LRC 48, which came with twin DD 4-53 @ 110hp.

    If you haven't experience bad handling at less than "planing" speed, I'm feeling a little bit of love for these fuel sippin' Fords.
  18. Seafarer

    Seafarer Senior Member

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    Check the Huckins thread to see a 65' planing hull running, without the quotes.
  19. q240z

    q240z New Member

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    Seafarer, I don't understand what you mean. What Huckins thread and what quotes?
  20. Seafarer

    Seafarer Senior Member

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