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1977 37 470 engine running poorly under load

D

daveolejnik

Member
"I Have a 3.7 mercruiser. I pu

"I Have a 3.7 mercruiser. I put new plugs and plug wires on it and changed the oil to get it ready for spring. It runs great, but when you put it into gear you cant get over 2000 rpms and cant even get the boat up on plain. The prop is a little dinged up,but I didnt think it was that bad. Also I dont know anything about points, in the distribuiter. But seeing it ran so good until under a load I thought everything was ok. Also I put regular plug wires for an electronic egnition on the engine, And my grandfather said He thinks they use differant wires for the older point style dis. When in nuetral the motor runs great and will go to 5-6000 rpms, but in drive your lucky to get 1700rpms. I know I can change the pitch on the prop, but I am not sure if the prop is the problem, or if it is in the engine. Any info would be greatly appreteated."
 
"Dave
Your not getting enough

"Dave
Your not getting enough fuel, when it runs great no load, doesn't run great with load means fuel sat to long and is clogging fuel jets or, possible pump or filter problem. Put some Sea Foam in the gas and run it try to clean out the carb or injectors, change any filter in system"
 
"If there is not a lot of fuel

"If there is not a lot of fuel, you can also dilute with clean new fuel.

Doubt you have plug wire issues as electronic ignition and points ignition should use similar wires and not cause your simptoms.

Consider checking the points as well if you have them. Will cause similar stubling and lack of power if you've got worn out points."
 
"Thanks for the help. Your pro

"Thanks for the help. Your probably right about the gas. I just bought the boat and I have no idea how old the gas in it is. The exhaust manifold gasket was out of it when I bought it, and the plug wires were bad. So it might not have ran for 1-3 years. I just assumed the gas was alright, when I got it running good (in nuetral). I will drain the gas, change the filter, clean the carb, and replace the points, and check the advance. Thanks for all the help, and I will let you know how it runs in a few days. (When it warms up again)."
 
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