Mercruiser 4.3 Help

[Hamil007]

I have a 2002 Regal 2765 with twin Mercruiser 4.3's. The starboard motor has been performing strange. Sometimes it does not want to start right away, but then it idles fine. When trying to plane the boat, this engine is running approximately 300 rpms slower than the port engine. Also, when revving in neutral, the starboard engine revs slower and appears to be sluggish.

I changed the fuel filters and this did not help any. My next idea is to replace the spark plugs.

Does anyone with knowledge of this engines have any advice on what to try next? Thanks in advance!

 

[r.j.dawg]

Welcome to iboats. You really need to post your engine serial numbers before anyone can provide and constructive help. I had twin 4.3's in a past boat but without knowing exactly what you have....I would hate to give out some potentially damaging advice.

 

[achris]

Hello Hamil and :welcome: to iboats.

The 4.3 comes in many flavours, which particular ones do you have? (L, LX, LH, LXH, MPI, EFI, TKS)

Chris......

 

[Hamil007]

The engines are MPI's.

 

[achris]

The engines are MPI's.

Ok, MPIs.. Have one, and the software for computer diagnostics. I also have 2 friends with one each that I maintain and a third about to buy one. Do I qualify?

For your problem, I would be putting the computer on and making sure all the parameters are in the right zones. Check the operation of the IAC, and the accuracy of the tachos (the computer program has a pseudo-tach generator. Great for checking tacho accuracy without even running the engine. It also has an injector bank cut test.

A couple of things worth looking at is the 'in-gear' sense switch. And the IAC (idle air control). As you have 2 engines, just swap the IAC from one to the other.

The other option, and as you have 2 engines, I would suggest it, and especially if you have friends with MPI engine (V6 or V8), buy the software and hardware connection kit. Even if you can't read into the results, you can post them here and we can interpret them for you. Look at www.Rinda.com and look for the Diacom software, with the various harness connectors. It's not cheap, but mine has paid for itself already.

The software won't always tell you what's wrong, but it can certainly rule out a heap of things....

Chris...........