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1994 40HP Mercury lack of power

R

rmmustangs

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"I have a 1994 40HP 4 cylinder

"I have a 1994 40HP 4 cylinder Merc that runs great idles smooth and when run with the muffs on revs great, but when in the water and in gear and under load it seems like I'm not getting full power or RPM's. Any idea what might be causing this? Any information would be appreciated."
 
"You need to check the compres

"You need to check the compression and spark on all cyl's. It might be running on 2 or 3 cyl's, hard to tell in nuetral. Certain death of a 2 cycle engine is a fuel/carb problem. A plugged jet on 1 carb means half the engine doesn't get fuel or OIL. Running in this condition ruins the engine."
 
Thanks for the info. I did a c

Thanks for the info. I did a compression test and all 4 came in at 120+ and all have spark. Do you think the carbs may need a rebuild? Thanks
 
"Is this motor new to you or i

"Is this motor new to you or is this a problem that just poped up.

It could be anything, carbs, electrical, or if its a new to you boat, over pitch prop.
Are you making max rpm?

As I said, if one carb goes and you run it, problems will happen, thats why we check the compression to see if a carb wiped out the engine. To be on the safe side, if the engine sat, overhaul the carbs. Be certain the main jet is clean.

A little more info might help."
 
I purchased the boat in April

I purchased the boat in April of this year. Prior to me buying it it had been sitting in the garage for about a year unused. I have only had the boat out 3 or 4 times and sometimes it feels as if I get full power (or rpm's) and other times I don't. I think I'll try the carb rebuild and see if that clears it up. As for the prop I don't see any markings on it at all so I don't know if its the correct one or not. Thanks for the input.
 
"Ok, try pumping the fuel bulb

"Ok, try pumping the fuel bulb while the engine is not producing full power, this will tell us if its a fuel pump or supply problem. As far as the prop, if it made full power before with that prop then it should again. To determine the best prop for max speed we need to know what max rpm is with 1 person in the boat, minimum load(beers). This can't be done till the engine runs right. Clean carbs is the safe way to go. You can put a timing light on each plug wire while running to check for a good consistent spark"
 
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