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Low power when put in the water

M

Michael1234!!!!

New member
Motor runs good when on muffs but once I put it in water it seems to only be half throttle. 40hp only pushing boat about 12-15 mph. Give me everything to check cause it’s starting to drive me crazy
 
No it hasn’t. Had to redo the transom so cleaned carbs and all when i put motor back on. Boat hasn’t ran in about 10 years and I’ve been trying to get it going
 
It's worth doing a compression test. I learned as a young pup working at a dealer 50 years ago. Whatever the engine came in for, you do compression, spark, and gearlube check before you ever turn a wrench on it. If you have spark ( although it should be checked at 3/8 gap on a spark checker that most people don't have). If the engine hasn't run in 10 years, it could be anything, does one spark plug look wet and the other dry?
 
I’m gonna do a compression test when I get home this week and both plugs looks similar to me. The bottom one may be a little more wet than the other but it’s nothing drastic
 
fitz73222 said:
It's worth doing a compression test. I learned as a young pup working at a dealer 50 years ago. Whatever the engine came in for, you do compression, spark, and gearlube check before you ever turn a wrench on it. If you have spark ( although it should be checked at 3/8 gap on a spark checker that most people don't have). If the engine hasn't run in 10 years, it could be anything, does one spark plug look wet and the other dry?
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I’ve got about 65psi on top cylinder and around 70psi on bottom cylinder. That’s way too low right?
 
Also, Try another gauge. Or try that gauge on something that works well, say your lawn mower. If readings are still low, you have a bad gauge. Some of those Amazon units are poor quality.
 
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