1992 mercruiser 4.3L power loss (occasional)

[neilmw]

Might have mentioned this before,still havent solved the problem.......not been using the boat much over winter so will give it another go.
After 40 minutes of planing at 3500rpm power suddenly drops off,picks up then drops again and will continue to do this until engine eventually stalls. if left of or ticking over for a few minutes its fine again. for another 40 minutes ????

seems to run for hours at 2000rpm with no problem, have checked and cleaned fuel breather-anti-syphon-and visual check of inside fuel tank. according to the bills the coil was changed 1 year ago.
Any ideas would be great

 

[Gary H NC]

Re: 1992 mercruiser 4.3L power loss (occasional)

Maybe have the fuel pump pressure tested.Or throw another coil on and see what happens...could be defective.

 

[bruceb58]

Re: 1992 mercruiser 4.3L power loss (occasional)

Just to be sure it is not a venting issue, try running without the fuel cap on. Then if still a problem, try running off of a portable tank.

If that is not the problem, I think Gary is correct in suspecting the fuel pump.

Have you checked all of your filters?

This sounds like the same problem you had last September.

 

[neilmw]

Re: 1992 mercruiser 4.3L power loss (occasional)

Have changed the fuel filter, tried taking the fuel cap off and there was no change. will investigate the pump though

 

[bjcsc]

Re: 1992 mercruiser 4.3L power loss (occasional)

I'm not savvy enough to know what you have for an ignition system, but I was having a similar problem with my Jeep. I have a D.U.I. distributor in my CJ-7, and it is very similar to a GM HEI or the Delco EST in my boat. After installing headers, I would get wierd running including cutting out, etc. just like you. I also thought I had fuel problem. Turned out, after I spent a day trying to figure it out, that my ignition module was getting too hot. I shielded it, but the damage was done and it only lasted another month or so before it failed (no advance). The new one is still going strong and I have had no problems since then. At any rate, if you exhaust all your possibilities, this could be another one...

 

[Reel Poor]

Re: 1992 mercruiser 4.3L power loss (occasional)

I would recommend installing a mechanical fuel gauge between the fuel pump and the carb. Then run the boat till it starts acting up. The gauge will let you know if the fuel pump is pumping fuel to the carb.

 

[ziggy]

Re: 1992 mercruiser 4.3L power loss (occasional)

installing a mechanical fuel gauge

i don't understand what kind of mechanical fuel gage rp. a mechanical fuel pressure gage?

 

[Don S]

Re: 1992 mercruiser 4.3L power loss (occasional)

Here is a link on how to test your boats fuel system. (Not fuel pump pressure).

http://www.iboats.com/bbboard/bbBoard.cgi?a=viewthread;fid=24;gtid=1107009

Also have a look at the small wiring harness between the distributor and the ignition module. I've seen those get corroded and cause exactly the problem you describe.
The warmer it gets the more resistance in the connections and the more the problem shows itself.

 

[sabastianunf]

Re: 1992 mercruiser 4.3L power loss (occasional)

You may have sediment in your fuel tanks that you can not see and your new fuel filters could already be clogged again. My boat use to do the same thing all the time until I replaced the fuel tanks. Get a clear fuel filter so you can see if it is collecting any sediment. Also there is a small fuel filter where the fuel line goes into the carb which could also be clogged.

 

[Don S]

Re: 1992 mercruiser 4.3L power loss (occasional)

Get a clear fuel filter so you can see if it is collecting any sediment.

Clear fuel filters are not CG certified for I/O use in a bilge. IO's use aluminum bowls. The clear ones are mounted outside the engine compartments for outboard motors.

 

[Reel Poor]

Re: 1992 mercruiser 4.3L power loss (occasional)

installing a mechanical fuel gauge

i don't understand what kind of mechanical fuel gage rp. a mechanical fuel pressure gage?

This is a fuel pressure testing gauge set with just about all the adapters you would need to check just about any fuel pressure system. They are kinda pricey but very useful. With this and a vaccum gauge there is no part of the fuel system you can't check.

 

[neilmw]

Re: 1992 mercruiser 4.3L power loss (occasional)

Wow thanks chaps, great ideas to try !

 

[neilmw]

Re: 1992 mercruiser 4.3L power loss (occasional)

seen a few fuel pressure guages, once installed would it be ok to leave it as a permanant feature or could the guage cause problems? just thought it could be useful.

 

[Don S]

Re: 1992 mercruiser 4.3L power loss (occasional)

No, you don't want to leave it in the system. The hose is not marine rated and the fittings are usually plastic.
It's only a tool.

 

[neilmw]

Re: 1992 mercruiser 4.3L power loss (occasional)

Ok, going down tomorrow to check the wiring on the ignition module.

 

[bretz57]

Re: 1992 mercruiser 4.3L power loss (occasional)

unplug wiring harness and make sure its not all coroded. happened to me. would lose all power after running awhile, and all it was was corrosion

 

[bruceb58]

Re: 1992 mercruiser 4.3L power loss (occasional)

unplug wiring harness and make sure its not all coroded. happened to me. would lose all power after running awhile, and all it was was corrosion

3 year old post