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1982 Mercruiser 140 wont accelerate

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apoc330

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"I have a 1982 Wellcraft bowri

"I have a 1982 Wellcraft bowrider 180 with a mercruiser MCM 140 4cyl engine. When I run the engine out of the water on mufflers it idles great and the acceleration seems to be good can run it up to 4500rpm's + with no problem.

I put it in the water for the first time since I completed the restore on it and it idles out past the wake zone just fine but when I try to accelerate it barely gets above idle speed and the rpms barely raise over 1500 or so.

The carb has been rebuilt, new spark plugs, cables, and points. Oh yeah and when I pulled it back out of the water and put it on the mufflers it ran great again so it seems to be a load issue.

Any ideas or suggestions would be greatly appreciated."
 
"Ok, the first thing I would o

"Ok, the first thing I would of said was to check your carb, but you rebuilt it so thats out. Did you change your fuel/water separator? Hows your prop? Is is banged up? Did you recently change it? Is your ignition coil getting hot? Possible bad coil. Any fuel line kinks? Blockages? etc.... Last thing I would also do a compression check. Heads could also be tulip from old or bad fuel."
 
"The first thing I thought of

"The first thing I thought of was the prop, I checked it and it is pretty dinged up so I am going to change it. I havent checked the ignition coil to see if it is getting hot but I will and I replaced all of the fuel lines so they should be good. If the prop does not work I will try the compression test.

Thanks for the suggestions."
 
If the prop is dinged up in ce

If the prop is dinged up in certain areas it will cause cavitation. The right prop makes a world of a difference. Bad/wrong prop can make your engine work twice as hard.
 
Take a timing light w/you next

Take a timing light w/you next time out to see if you are getting any timing advance under load. You do have oil in the OD??
 
You don't really say how i

You don't really say how it's running. Is it missing or spitting and sputtering when you hit the throttle? Is it smooth but just no power? Does it rev up but not go anywhere? Does it cut out and die completely? More details would help.
 
"It runs very smooth no spitti

"It runs very smooth no spitting or sputtering when I throttle up, it just has no power and the rpm's don't climb, pretty much stays at idle speed.

I can turn it off and it starts right back up with no issues at all."
 
"check the throttle cable, at

"check the throttle cable, at the carb, to make sure it opens the throttle plate all the way. Maybe the cable isn't hooked up correctly."
 
"If it were the throttle cable

"If it were the throttle cable wouldnt the issue be the same in or out of the water?
Also, John P asked me about a fuel water separator and I dont think my engine has one. Is this something I can add easily? Forgive my ignorance but this is my first boat so I'm in a pretty steep learning phase."
 
"...it ran great again so

"...it ran great again so it seems to be a load issue.... it just has no power and the rpm's don't climb..."

The engine idles and revs fine; too high w/o a load. Limit it to 1500 RPMs on muffs. Put the boat in the water and no go. Perhaps it's time to check dry and wet compression of the cylinders.
 
"I am going to add the fuel wa

"I am going to add the fuel water separator this weekend for sure, sounds like a good thing.

I am assuming I will need to take it to a mechanic to check the dry and wet compression or can guages for this sort of thing be purchased fairly reasonably? I have the manual, would that have the specs for both wet and dry compression?"
 
You can buy the gauge at an au

You can buy the gauge at an auto parts store. It has instructions. Engine should be warm and throttle open. Remove the plugs and ground the coil output wire. Connect the gauge and crank the engine several seconds and record the number. Do it for all cylinders. Repeat the test but squirt a tablespoon of engine oil in the cylinders first; record the readings.
 
"If it revs smoothly I doubt i

"If it revs smoothly I doubt it's water in the fuel becasue it will spit and sputter. But a filter is a good thing to add and cheap insurance.

Have you checked your timing? If it was way off towards retarded it could run smooth but have no power under load. Make sure it's not 8-10 degrees AFETR top dead center, it should be before.

I'll admit I did that once on an old car I tuned up (a long time ago). It ran but had no power at all and got so hot it melted the rotor and cap! After replacing everything and retuning it it actually ran great. That's a testament to the old subarus."
 
"Thanks for the info on the ti

"Thanks for the info on the timing and I think I left part of the story out, it did start to get hot when I tried to accelerate for any length of time, but as long as it was running at idle it seemed ok, I didnt take it out very far so I was able to just idle back and it never seemed to overheat.

Going to go an check the timing now and will keep you posted."
 
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