Click for Cross Click for Nordhavn Click for Northern Lights Click for Westport Click for Abeking

Engine survey, 6-71's TI in good condition.

Discussion in 'Engines' started by dennismc, Feb 6, 2019.

You need to be registered and signed in to view this content.
  1. dennismc

    dennismc Senior Member

    Joined:
    Jan 29, 2009
    Messages:
    1,175
    Location:
    Vancouver BC
    OK, next step the mechanic want to run at wot for 10 minutes to check all temps , engine power output and any other issues that may come during that event. airbox inspection indicates approx 40% wear , no scoring all rings good.
    I was a bit taken back as I was under the impression that in pleasure craft with recreational use that a max of 2-3 minutes was the acceptable time for that run up. High idle was fine, ran up and held at 2200 with no issuesm may need a rack adjustment after load test.
    any comments appreciated.
  2. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,432
    Location:
    Fort Lauderdale
    Usually we do WOT for 5 minutes...….but if all is well they should go 10 minutes without issues. You should be a lot higher than 2200 rpms though WOT I think 6-71's are WOT of 2600 or 2800 rpms, I forget.
  3. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,649
    Location:
    Satsuma, FL
    Yes, High idle should be around 2600 for TIs.
    WOT in gear should be 2350. 10 minutes is a bit more than our trials but it will do it.
    I'm confused with; may need a rack adjustment after load test. Who said this and why?
    It's a simple and reliable rack once set up correctly. Operating at any speed will not alter any settings.

    I recall your running 12v71s now? It's the same engine setup.
  4. Pascal

    Pascal Senior Member

    Joined:
    Feb 29, 2008
    Messages:
    8,120
    Location:
    Miami, FL
    I m pretty sure 6-71s are 2300 rpm motors so 2200 is a BIG a red flag depending.

    10 minutes on the pins is a bit long. 3 to 4 minutes is what most surveyors do. It s not unusual for temps to creep at max rpm.
  5. Bill106

    Bill106 Senior Member

    Joined:
    Jan 9, 2010
    Messages:
    390
    Location:
    Beaufort NC
    Way back in the day many of the older guys who worked at Covington (once the local Detroit dealer) used to do startups on the dyno after full rebuilds by a full power under load run of 15 minutes or so after they came up to temps. Not all of them made it and I saw some pretty spectacular block ventilations but those that did almost always went on to long lives. If they're propped right and are hitting the governor at WOT there shouldn't be a problem but if one pops up it was likely going to happen soon anyway.
  6. dennismc

    dennismc Senior Member

    Joined:
    Jan 29, 2009
    Messages:
    1,175
    Location:
    Vancouver BC
    Helping a friend on purchase of these 6-71's, the high idle was close to 2200 I noticed on the guys tack was a look before going down to 600 low idle so I may be mistaken , all to be reconfirmed after we have done sea trial and load test , one turbo was not fully free turning and would bind ever so slightly, mech. would not accept responsibility for any sea trial WOT issues after finding that. so turbo in the dr's office getting overhauled. we have no confirmed background on previous readings of rpm's under load , hopefully next week we do that, we ran up my 12-71's after rebuild to 2100 pinned as we had downsized the injectors a few years earlier, if memory is correct about 5 mins was the timing on those runups. after shut down we discovered a stuck injector, luckily in the no fuel position, fixed that and re test all good.
  7. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,432
    Location:
    Fort Lauderdale
    You're 2100 rpms on your 12v71's is too low and you need to cut the props if you want them to live a happy long life. I ran a set of 8v71 TI's with downsized injectors and they ran great, crystal clean, but you must cut the props to match the reduced HP and still achieve WOT rpms
  8. dennismc

    dennismc Senior Member

    Joined:
    Jan 29, 2009
    Messages:
    1,175
    Location:
    Vancouver BC
    Good point, Tks.

    Probably easiest way is to go back to N70 injectors, the 65's where put in many yrs ago as a recommendation from a DD mechanic, no suggestions to recut props or otherwise, am now in contact with dealer for explanation of lower wot rpm and not advising of potential issues..at that time I was a true diesel novice, still am in actuality. again, thanks for the great feedback.
    Last edited: Feb 7, 2019
  9. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,649
    Location:
    Satsuma, FL
    IMO; All 71s should at least have N60s, I prefer N90s on 4 valve heads (TIs or Ns).
    If you want to run cheap, pull that throttle back.
  10. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,432
    Location:
    Fort Lauderdale
    Yeah, I've never heard of 60's on a 8v71 TI, the ones I ran went from 110's to 90's when they did the overhaul.