1995 Mercury 115hp. Wot bog

[Lk40hp]

Hi, I have a 95 mercury 115. It starts, idles, and runs great except for wide open. Wide open it's about 4500rpm. If you feather the throttle back to about 3/4 to 7/8th throttle it'll jump up to 5000rpm. But if you push it back to wide open it bogs back to 4500rpm.

I tried running it with 1 plug unhooked to see what cylinder it's not firing on but it only pulls 4100rpm on any 3

Any ideas?

 

[Chris1956]

It may be a fuel restriction. See if pumping the primer at WOT fixes it. If so, look for air leaks in the fuel line, dirty filters, clogged antisiphon valves or a clogged fuel tank vent. That motor should have a 5/16" fuel line. Smaller will starve it.

 

[racerone]

Start with a compression test.----Post your numbers.----Run with a timing light 1 cylinder at a time to see if you have spark issues.

 

[Dave1027]

Also to add, if pumping the primer bulb helps, look at the fuel pump. If the fuel pump has never been refurbished, it's due any way.

 

[flyingscott]

Test your stator high speed windings are a known failure on those.

 

[Lk40hp]

Compression test shows 145 across the board +/- 3psi. How do you test the high speed windings?

 

[Lk40hp]

Also I can check with a timing light, but cranking it shows a healthy spark on all 4.

You're saying get a buddy to drive the boat and test spark with a timing light while it's having its issue at 4500 rpm?

 

[flyingscott]

Get a factory manual or buy the ignition guide from CDI and test the stator.

 

[racerone]

Drive the boat.----Lay timing light on a seat so you can observe the flashing light.-----Steady flashing indicates steady spark.

 

[jimmbo]

The carbs shouldn't go past Wide Open, but not knowing the History of the Motor, I would recommend checking to see if the Carbs aren't going past Wide Open, and are closing again. As I said, they shouldn't but

 

[Lk40hp]

Finally got to testing it. Steady flashing on all 4, priming bulb Also doesn't help