Crusader 454 losing RPMs

carb or fuel injection? I'd check fuel pressure. A weak fuel pump may not deliver enough fuel to keep the carb bowl full at cruise rpm. At idle it will refill the bowl(s) and next time out the engine runs ok for a while and then bogs down again.

How does it respond the next time out? Does it run ok for a while and then start to lose power? This would be indicative of a fuel delivery problem to the carb.

Changing fuel filters is relatively cheap and easy. Fitting a fuel pressure gauge requires a bit of care but can be done. I have had a fuel pump deliver normal pressure right up to about 2500-3000 rpm and then drop off slowly to 0. This only occurred under load. At the dock it was fine. You will need a mechanic and an operator to test this. If the operator cannot see the mechanic while operating the boat then you should also have a spotter.

You can get a dial back to 0 timing light for around 50 bucks which will give you total advance. You can check both engines to see if there is an issue with the timing advance. Most likely it is mechanical (It could be electronic or vacuum) Assuming it is a mechanical advance you would not expect the springs to contract and stick while they were already providing advance and the engine running properly. So from your description that is unlikely.


PS. Saw your post on the other forum also.

I second the fuel pump. We travelled from Upstate NY to SC last fall. Never had a problem until we reached the Delaware Bay. We travelled the whole trip at 1500 to 1800 RPM. We wanted to speed up to get off the bay and cruised at about 3300 rpm for about 1 hour. Then the RPM's started to drop to approx. 2000. Investigated the problem in SC and discovered the fuel pump wasn't pumping anough fuel to maintain +3000 RPM. Replaced the fuel pump and no further problems. Those 454's really like the fuel at +3000 RPM's.

I'm sorry I really can't. I've been diesel for 6 years now and my current mechanic only does diesel work. I did most of the work myself on the gas engine so I don't even have an old contact.

I agree I would start with fuel pump first.

Although I have 350's, as I was driving my boat home for the first time after purchase, my port kept losing power down to about 1200. I could bring it down to idle, then power it up again for about 4-5 minutes before it would happen again.

Strangely enough it was the beginning of my distributor going bad. Not the cap nor rotor, but the actual distributor 'shaft' that goes into the engine.

Sounds serious. Lobes on the Dist. shaft? How many hours on the engine?

The distributor shaft was ok, but something to do with the assembly and some electronics on the top were shot. Before long the engine wouldn't start at all. I really don't know much about it; my mechanic used his meter and probes to determine it went bad. I believe it had around 600 hours on it. We've replaced the block since then due to internal bearings going bad.

Actually check the fuel tank vent even before that. I've seen on gas boats where the vent got clogged and when you went to cruise the tank had too much vaccuum and the mechanical pump couldn't pull enough fuel.

Fresh water cooled (heat exchanger) engine would be 185 degrees. Sea Water cooled (no heat exchanger) engine 145 degrees.

Yes, change it to the correct thermostat for the engine. Not sure if it would be 195 or not but definitely in that range. The 145 is a compromise to keep mineral deposits from building up too quickly when sea water is pumped through the engine. However putting a raw water thermostat in a FWC system is a pretty odd screwup. Or a pretty amature one. At some point somebody who didn't know anything (or didn't are to) worked on those engines. I'd also verify that the correct radiator caps are on those heat exchangers.

What I would do first...

I would start with running the appropriate amount of Sea Foam Motor Treatment (engine cleaner) through each fuel tank first. I have 25 year old 454 Cursaders that were topping out at 3600 rpm when they should be at 4400 rpm. I put 2oz per gallon of gasof of Sea Foam in each 200 gal fuel tank had them purring at 4200 rpm afetr 30 minutes of cruising. I didn't push them any further as I rarely have the boat over 3000 rpm. Did I mention it's 25 years old...

I have a 1990 Carver 3607 with twin 454 Crusaders and last summer had the same type RPM problem, the longer I ran the worse it got. I got the same advice about fuel pumps. I guess I'm just contrary but I replaced the plugs, wires, distributer cap and rotor. Problem solved, engine now powers up to 4600 rpm and holds it.