1983 mercruiser 260 350cid Low RPM issue

I have a 1983 mercruiser 260 that has been rebuilt a couple of times. On the last rebuild, the mechanic said that he couldn't get a lot of RPMs out of it. Currently it tops out at 3,000 RPMs. Brand new, the motor did 4,600-4,800 rpms.

Is this common? or did they really screw something up? Low compression?

Is there anyway to restore the high RPMs?

 

the advance has seized in the distributor

the secondarys in the carb are not working

rebuilt a couple of times....what was diagnosed
Does it have all original components?

 

A rebuilt motor should get the same RPMs as a new one, once it's broken in a bit. The mechanic should not have charged you for a rebuild if he can't make it work properly.

 

Was it rebuilt because of low RPM? Certainly the secondaries would be a good bet.

 

The last rebuild was... if I recall right... from a valve hitting the piston.

If the secondary's are not working, is that generally a replacement or can I clean out the carb to get them working again? I'm new to carbs. I've cleaned them before, but they were smaller and simpler designs than the boats carb.

Should the mechanic have retimed the advance when the engine was rebuilt? I'd assume that he would have done that, but you never know. We got the rebuild done for cheap because we are very close friends with the marina owner. I'd say it is safe to assume that it still has original ancillary components.

Thanks for your responses. I am looking forward to getting to know marine engines better. I've already learned a boat load

 

Does it still have the original Rochester Quadrajet carb?
If so you will need someone to show you how to pull that apart or buy a book
post a photo

 

I'll check.... might take a day or two to get out there. I'm guessing it is still the original.

 

Was the engine running ok before the valve and piston deal?

 

If your mechanic noticed "he couldn't get any RPM's out of it" then he darn well knew what was wrong and that it was probably his fault. He screwed up, it happens, but you don't have to pay for it. If he doesn't make it right, then small claims court will quickly clear up the mess. He also knows this, so call him and get the real story or make him pay to have it done right thins time (which is what the court will force him to do).

 

I can't recall at this time. It got rebuilt 4 years ago.

 

The boat wasnt in the marina was it. Im thinking fouled prop.

 

If it was a fouled prop, the mechanic would have been able to rev it up out of gear, but that's not what he said. If he had something other than himself to blame, you can bet he would have.

 

The prop is fine. It runs the same with an old prop or a new prop.

Is low engine compression a possibility?

The boat starts easy and runs smooth, it just can't get the RPMs up past 3k

 

Nope, even with low compression (which you shouldn't have after a rebuild) the engine should pull a full set of RPM's. It's likely he reused some parts that should have been replaced and is making excuses for it. It could be as simple a distributor advance spring or a stuck weight.

 

Agreed.