Mercury 35 Low RPM / Lost Power

A

Adaboat

Cadet
Joined
Aug 31, 2010
Messages
12
I have a 1986 Mercury 35 mounted on a 13' Glasstream fiberglass bass boat. The last time I used the boat it was running great around 5000 RPMs and suddenly slowed. The gas was low so I thought it was running out of fuel so I went to shore loaded the boat and went home. When I put the boat back in the water it still wont go but around 1500 RPMs at WOT. It cranks up great, idles good, has 150psi commpresson on each cylinder, new primer bulb/hose. At WOT the carb butterfly is wide open. It runs smooth, no skipping or smoking, just wont get over 1500 RPMs. Any suggestions? Thanks!!
 
A

Adaboat

Cadet
Joined
Aug 31, 2010
Messages
12
Re: Mercury 35 Low RPM / Lost Power

Okay I got my manual today....so far not much help. It don't have a troubleshooting section like I hoped for. Does anyone think the stator could cause this problem? Gonna try to test it this weekend.
 
W

westjr8

Seaman Apprentice
Joined
Mar 13, 2011
Messages
35
Re: Mercury 35 Low RPM / Lost Power

Compression seems good. I would also take your boat in the the local mechanic and have them check to make sure you have spark to all cylinders. If you have fire in all cylinders, I would then start thinking about the fuel system.

Is the gas tank vent stuck?
Have the carbs been cleaned/rebuilt?
Has the fuel pump been rebuilt?
Is the fuel filter clogged?
 
saumon

saumon

Lieutenant
Joined
Aug 2, 2004
Messages
1,452
Re: Mercury 35 Low RPM / Lost Power

A spark in all cylinders isn't enough, you need a STRONG spark, being able to jump a 7/16" gap. A lot of people are being fooled by this, checking that there's a spark and then moving on to the fuel system.
 
A

Adaboat

Cadet
Joined
Aug 31, 2010
Messages
12
Re: Mercury 35 Low RPM / Lost Power

Gas tank vent is working properly, the carbs have been cleaned, Fuel pump has not been rebuilt but seems to be working properly, when squezzing the primer bulb when running it didn't make any difference. I have fire on both cylinders but not sure how strong it is, it's a blue ark. I was reading some other post that said the Stator has a "Top End" RPM. Could this be the problem? If I run the OHM test the manual talks about will this reveal this?
 
A

Adaboat

Cadet
Joined
Aug 31, 2010
Messages
12
Re: Mercury 35 Low RPM / Lost Power

Motor cranks and runs fine in idle. When you are on the water and move to wide open throttle the engine only turns about 1500 RPM. Runs smooth but not fast, no spitting or sputtering or anything. It's like it's in limp mode. Is there anykind of "reset" switch? Does anybody think a stator or Trigger coil could cause this?
 
You must log in or register to reply here.
Top