Thread: 2001 Mercucry 115 outboard

Problems Problems Problems 115 Mercury

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I have a 2001 115 Mercury outboard and it started out going 36mphs ran fine for years.Now when i try to [plane out it will not reach max speed only about 24mphs and then it will slowly drop speed and rpm down to about 8mph.The whole boats starts shaking and this will continue untill i pull the throttle back off and start over.Then i am lucky to get back in to the landing. Installed new plugs,drain gas tank clean put new high octane gas and sea foam. Also check fuel injectors and they are firing okay,checked psi on fuel legs and it also holds up?????Any help is appreciated????

Are you sure your throttle linkage hasn't slipped and preventing it from opening up all the way?

Doesn't sound good, but I'm hoping it's something simple.


Wannabe...

Stop wasting money on high test gas. Your motor isn't engineered for it and it doesn't help a bit. Rebuild your fuel pump and be sure to get the kit from Merc as they contain new style check valves. Merc has a TSB out on that and I use to have access to it but Merc made the site remove them. I guess they don't want us to know what's wron with there motors.

Originally Posted by IBNFSHN

Stop wasting money on high test gas. Your motor isn't engineered for it and it doesn't help a bit. Rebuild your fuel pump and be sure to get the kit from Merc as they contain new style check valves. Merc has a TSB out on that and I use to have access to it but Merc made the site remove them. I guess they don't want us to know what's wron with there motors.

The dealer told me NOT to use high test gas, reg only and use the Quicksliver fuel additive. Said the high test would cause carbon build up.

I think the problem with the higher test octane is that it promotes detonation of the fuel charge and burns hotter than the regular. Potential for Kablooey in other words.

Wannabe...

have you done a compression check on the cylinders? that should be the first thing you do....then check spark....then fuel.......compression,spark and fuel and a motor will run.

may not apply to this but I had an older 10 hp that was doing close to the same thing. It turned out to be the power pack and not firing all the plugs when it was suppose to

Ok, ya'll making me get back into my old hot-rod drag car mentality here
talkin about octane...

High-test. High Octane. LESS detonation. HARDER to ignite.
CAN do funny things with heat because it is harder to ignite, so it
burns LATER over into the cycle...
Octane is basically ignition retardant.

Some of the really high octane race gas, I have been told on good authority,
if you poured it into your average passenger car, it would not even run.
It needs high compression ratio and hotter spark to burn.

Originally Posted by J White

Ok, ya'll making me get back into my old hot-rod drag car mentality here
talkin about octane...

High-test. High Octane. LESS detonation. HARDER to ignite.
CAN do funny things with heat because it is harder to ignite, so it
burns LATER over into the cycle...
Octane is basically ignition retardant.

Some of the really high octane race gas, I have been told on good authority,
if you poured it into your average passenger car, it would not even run.
It needs high compression ratio and hotter spark to burn.

This is true.

Hey guy's
Thank's for all your input, I have taken the boat to the local marina to be repaired HOPEFULLY.
When i get it back i will post a update
I have had a compression test and just fustrated with the whole thing.
I have turned my attention to the pontoon,
Thanks