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4.3 LX - Possible fuel/carb/choke issue?

mike523

New member
New boat owner here, and I'm already wondering if it was a horrible decision haha. Long story short, first time out on the water had a ton of issues, timing chain cover broke spraying oil everywhere and I had to get it towed back in. Luckily seller is a good man and tried to help fix things and paid for half of the repairs (harmonic balancer broken, water pump cracked, timing chain cover replaced, put new plugs in, changed oil) but 1st time back out on the water after repairs I had the same problems.


Boat idles fine but throttle response is terrible and if you go wide open she bogs down, won't get over about 25 mph or around 2500-3000 rpm I think. Backed off the throttle and she ran for about another 30-45 seconds before dying and I was dead in the water. Took about a half an hour to get her to start up again and limp back to the boat ramp making a TERRIBLE sounding racket kind of like squealing belts but also sounding a bit like metal on metal. Also, checked the dipstick and the oil seems pretty thing and watery and its hard to tell but the strange smell is probably fuel in it.


Here's a short video I made so you can get an idea what it sounds like.
https://www.youtube.com/watch?v=OR5_8eZ_qGE
 
Just a possibility. Don't know what kind of engine yours is "but" might be the fuel pump went bad if it is a mechanical pump. "Maybe" diaphragm ruptured and dumped gas in oil pan from you description. Not really enough info for diagnosis.
 
Just a possibility. Don't know what kind of engine yours is "but" might be the fuel pump went bad if it is a mechanical pump. "Maybe" diaphragm ruptured and dumped gas in oil pan from you description. Not really enough info for diagnosis.

Yeah I know I don't have a lot of info - its the Mercruiser 4.3LX Alpha 1 Gen 2 i/o setup though.
 
Ayuh,.... Do a compression, 'n leak-down test,.....

Sounds like it was runnin' Lean, 'n ya detonated it to death,...
 
Detonated to death...we talking pistons and rings?

As "Bondo" said, do a dry/wet compression test on each cylinder. That would be a very good place to start troubleshooting to let you know the condition of your rings. Post your readings here so members will have a better idea on how to advise you on your next step.
 
Compression and Leak down test. Wet/dry will not tell you.

If you find a few dead holes, time for a long block.

Pull the belts off and see if the squeak noise goes away.

If not, sounds like a wrist pin.
 
Ok so according to the mechanic its a bearing (if i understood him correctly its the main crankshaft bearing). Apparently this means the only solutions are:

A. remove and rebuild engine
B. replace with a different 4.3
C. if i'm going to replace the motor, maybe move up to a 5.7, possibly increase resale value of the boat

Any thoughts here?
 
Ayuh,.... Go with B,....

With C, you'll need a different drive, as the ratios are very different,.....
 
Ayuh,..... Commonly available props run from 15" to 23",.....

Dependin' on the pitch ya had with the small motor, ya may not be able to prop it high enough to compensate the difference,....
 
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