Logo
FULL SITE MENU

1988 Merc 25hp

J

joho5

Member
"My dad has this motor and we

"My dad has this motor and we are having troubles. It starts and idles fine most of the time, but it wont top out. It runs smooth and sounds fine, but just wont get to the top end rpm's. We changed out the coils because they were cracked.

The guy he got the motor from has a Johnson/Evinrude gas fitting on the tank. So the gas line has 1 end Johnson/Evinrude and then the other that connects to the motor is Mercury. Could that be a problem with air?

the next thing we are going to do is pull and clean the carb.

If any has any other suggestions about why it wont run at top end, please let me know. I only own Johnson and Evinrudes so I am inexperienced with a Merc motor.

thanks

Matt"
 
That gas fitting is fine. I ra

That gas fitting is fine. I ran one like that for years. You could have some clogged high speed jets in the carb. When you rebuild that I would also rebuild the fuel pump. Be sure to get the kit from Merc so you get the new style check valves.
 
"is the jet, just the bottom s

"is the jet, just the bottom screw that screws off and works as the bowl plug? Or is the jet the passage way all the way up to the throat of the carb? if so, how does that come out? which jet is the high speed? I pulled the carb today and cleaned it as much as I could, but I would like to double check the high speed jet.

thanks"
 
"Matt, the "passage" i

"Matt, the "passage" is cast/pressed right into the carb and doesn't come out. That's why usually you will disassemble and soak the entire carb, then blow some compressed air up the tube to get the last of the "cooties" out.

There's no other real easy way to do it..."
 
"We found the potential proble

"We found the potential problem. That passage is actually been bent...therefore when you screw the bottom bowl plug / jet in the bottom, it wasnt having the passage seat right in the jet. It was off to the side and then bowing up that passage. What we are going to try is sticking something in the hole from the other side and straighten it out while putting the bowl plug / jet back on. Im sure that was the problem, you can shine a light through there and see all the way though...its clean. I just think that passage wasnt seating with the jet correctly, causing inconsistent performance.

any thoughts?

thanks"
 
"You want to be careful becaus

"You want to be careful because if it gets screwed up you will have to replace the entire carb.

If you can find a Tap that fits, may be the way to go. At least it will screw in properly and give some support/less stress than using something else that may slop around when trying to realign it..."
 
Back
Top