2005 Merury 40HP 2-Stroke - 3-Cyclinder - Loss of RPM/Power

[BearKatt]

1st Timer:

I have just purchased a (used) 2005 Mercury 40hp, 2-stroke, 3-cyclinder outboard.

It stats fine. But, as soon as motor is warmed up, RPM/Pwer drops from 4500rpm to 3000rpm and of course, loss of speed.

Have drained carb bowl, 3 brass nuts, and replaced original; spark plugs with new. when replacing plugs, cyl 2 plug was wet, 1 and 3 were dry, I thinki means 2 was not firing(?)

Some good buds tell me it must be a coil failing once motor is warmed up.

Has anyone else come across this and could they provide actions and results?

Thank you,

BearKatt

 

[jrodgers321]

Re: 2005 Merury 40HP 2-Stroke - 3-Cyclinder - Loss of RPM/Power

My 50 hp is doing the same thing. If you find out what it is please post what it was. I will do the same......
It doesn't seem to be ignition to me. Mine continues to run good, just lower rpm. If I throttle down, then gas it , it takes off then slows down. It is almost like a sensor is making it do what it does. I am thinking fuel, next time out I am going to shoot it with some eather and see what happens.

 

[BearKatt]

Re: 2005 Merury 40HP 2-Stroke - 3-Cyclinder - Loss of RPM/Power

You can count on it..., I've taken it to a marine mechanic and he's taking a look at it..., I'll advise of his findings and hopely, the solution..., just frustrating. This forum seems to have a lot of great information and advise, through networking with the experienced marine mechanics and vetern boaters who have been through the ropes a few times!!

 

[BearKatt]

Re: 2005 Merury 40HP 2-Stroke - 3-Cyclinder - Loss of RPM/Power

Hey, check your compression, my mechanic says my 40hp 2-stroke mercury is only at about 80???

sounds like I will need a ring job over the winter.

BearKatt

 

[Tido25]

Re: 2005 Merury 40HP 2-Stroke - 3-Cyclinder - Loss of RPM/Power

Could be a fuel problem you could rebuild your fuel pump and carbs or it could be a bad stator and it's acting up once it gets hot. Good luck

 

[bayouhntr23]

Re: 2005 Merury 40HP 2-Stroke - 3-Cyclinder - Loss of RPM/Power

I have the same motor with the same problem. So far I've replaced the fuel pump, cleaned and rebuilt the carbs, changed the water pump, gas, fuel lines, check the thermostat for proper operation and flushed the water passages. Still the same problem though. I guess my next step will be to bring it to a Mercury service mechanic. Anyone find a solution?

 

[123roger]

Re: 2005 Merury 40HP 2-Stroke - 3-Cyclinder - Loss of RPM/Power

I have a mariner bigfoot 60 with a similar problem. Runs fine for an hour or so, then will only run up to about 2200 RPM's. Please post findings. Thanks, Roger

 

[Faztbullet]

Re: 2005 Merury 40HP 2-Stroke - 3-Cyclinder - Loss of RPM/Power

You need to test engine when it fails to see if it has dropped spark to a cylinder. A bad CDM module can cause this along with trash floating in carb bowls stopping up high speed jet. If you drain fuel bowl capture the fuel in a small container and pour thru a white paper towel, if it has black specks in it the fuel lines are deteriorating internally....

 

[123roger]

Re: 2005 Merury 40HP 2-Stroke - 3-Cyclinder - Loss of RPM/Power

I'm more agreeable to the dropping a cylinder. I've replaced the fuel line, filter, plugs, drained the carbs, cleaned the tank and filled with fresh gas. I always use stabil. Everytime out it has run great for about an hour then will only run at about 2000 to 2400 RPM's. I was thinking stator,coil, powerpack or trigger. What's your best thought? Thanks, Roger

 

[BearKatt]

Re: 2005 Merury 40HP 2-Stroke - 3-Cyclinder - Loss of RPM/Power

Folks, I've given up and I will be taking my 40hp Merc to a Mercury dealer shortly and get it done, sounds like it could be a rebuild as the compression is so low 80psi+. As a novice, I should have had it checked prior to buying, rookie mistake on my part.

I want to thank all who have provided their input as all seem like great ideas, but as I am not a mechanic..., I'm stuck.

Lessons learned, eh!!

Getting it ready for spring up here in Belleville, Ontario, Canada..., once the ice is gone for sure, I can't wait to get it out on the water to do a little fishing with the grandkids and a few buds!!

Keep'er on the right side of the bouy's!!! LOL

Again folks, thank you all for your valued input!!

BearKatt