Mercruiser 4.3LX Engine Problems...Help Please!

[jserr68594]

I recently purchased this boat with a '94 4.3LX engine. Prior to my purchase, it had set for two years. Upon first taking boat out (When I first purchased it two weeks ago), it ran fine for the first 20 minutes or so. The engine started to cut out and surge at higher RPMs and stalled once. If I backed the throttle down it would stay running.

After having this issue, I changed the fuel separator, spark plugs, and added dry gas. I then filled the tank. It ran fine the next time I used the boat, but I only used a little over ? tank of gas. The next time I took it out, the engine started surging again. I did nothing other than fill the tank up and the surging went away. Towards the end of this trip though, I noticed a little power loss. Also, the boat would idle very low and want to stall at idle. It is very hard to start at this point as well.

The next time I took the boat out, the engine wasn?t surging (It only seems to surge when there is less than ? tank of fuel). There was however a considerable decrease in Speed, RPM and power. The boat would normally run around 4800 RPM/52 MPH with two people in it. I could barely get 4000 RPM and 40 MPH. It also seemed to use a lot of fuel. I changed the distributor cap & rotor and it ran the same. Battery voltages are good. I also noticed there seems to be steam coming from the engine bay on the port side. I do not know if the flywheel is spraying water from the bilge or if there is a leak in the exhaust.

It seems the boat does not surge with a full tank of fuel; however I am now dealing with this sudden lack of power. I do not know if these symptoms are caused by the same or different issues. The boat only has 268 hours as well.

Any input is appreciated!!

 

[achris]

Re: Mercruiser 4.3LX Engine Problems...Help Please!

Hi and welcome to iBoats...

First thing I would do is a compression test... Then check that you have a wire between the distributor body and the engine block. That year seem to have a problem with grounding between the dissy and the block... A bad ground to the dissy would account for a lot of your problems (but I can't see there being any correlation between the fuel tank level). Next check the anti-syphon valve in the fuel tank line, also pull the pick -up tube out of the tank and check it for leaks... A quick way to check for that is to temporarily put a clear section in the fuel line and look for bubbles.... You see bubbles, you have an air leak. While you're at it, put a vacuum gauge on the fuel line and make sure you're not get any more than 2" vacuum... If it's more, then there's a problem in the fuel delivery system....

Plenty for you to start with... Let us know how you get on.

Chris.....

 

[cr2k]

Re: Mercruiser 4.3LX Engine Problems...Help Please!

How old is the impeller? If you don't know it is too old.

 

[tpenfield]

Re: Mercruiser 4.3LX Engine Problems...Help Please!

No wonder the boat was for sale . . .

I'm also thinking that there is a problem with the fuel pickup and/or fuel pump. If the fuel pick-up line has developed a perforation due to corrosion, then if would only work when the tank was filled higher than the perforation. IF the fuel pump was tired, then a similar symptom would occur.

If it is an aluminum tank, then maybe corrosion has set in and there could be bigger issues. See what the tank looks like from the outside, etc. and post some pics, etc.

 

[jserr68594]

Re: Mercruiser 4.3LX Engine Problems...Help Please!

Thanks for the input guys! I am going to look into these things.