2007 40 hp losing power

[trapper 12]

My 40 hp is losing power intermittently when powering half power and up on one cylinder. Under half power and idling it don't miss a beat. Have checked fuel lines and clean the carburetor. Dealers in the area won't take a look at it till the spring and I need the motor working now.

[99yam40]

posting a complete model # and where this thing is located(country) may help us know what 40 this is

you make it sound like it is just a 2 cylinder motor, but I thought the 2 stroke 40 went to 3 cylinders long before 2007
do you have gauges or any LED indicators for oil or temp problems

[trapper 12]

The model is a f40mlhf 67c, 3 cylinder. It is a 4stroke and I am located in canada

[walleye1]

You need to explain in better detail. trapper.

[99yam40]

The model is a f40mlhf 67c, 3 cylinder. It is a 4stroke and I am located in canada

no gauges or led lights for trouble indicators?

possible low or high oil pressure (out of normal range) could cause RPM limiting
or could over heating

[boscoe99]

If you pump the primer ball when the motor starts to lose power what happens?

[trapper 12]

Last winter the water pump gave out and I had replaced it this summer. I also replaced the thermostat. No warning lights are on. It only happens when you power up over half throttle. I tried pumping the primer ball but it doesn't make a difference. When it starts to happen it well run good for about 15 to 20 seconds than sputter for a second or 2

[99yam40]

If you have lights, you need to make sure they function as they should.
I believe but not sure on that 4 stroke ,RPM reduction due to oil pressure or overheat should happen around 2000RPM .

verify good compression, and then oil pressure, spark, and timing at the problem RPM.
If all checks out then you are left with too much or too little fuel to burn properly

[TownsendsFJR1300]

Did you retrieve ALL the rubber parts of the WP impellor (IF it came apart)??

[trapper 12]

I took the cover off where the thermostat is to and flush it out. Done that a few times after having the motor running. And also took the lines off and flush out. But there still could be some in there because she don't seem to pumping out enough water. Also took the anodes out while flushing.

[walleye1]

You will have to pull the head and exhaust cover to get the rubber out, pull your water pick up screens off on the gearcase and look in there too.

[trapper 12]

You will have to pull the head and exhaust cover to get the rubber out, pull your water pick up screens off on the gearcase and look in there too.

Done this and picked out a handful of rubber and flushed out the lines

[TownsendsFJR1300]

The cover and the HEAD are two very different things...

There have been threads / posts where a small piece of impellor (broke off) caused over heating and other issues in critical areas...

You very likely cannot get to all the internal head/cylinder water jackets W/O pulling the head...

[walleye1]

You will have to pull the head and exhaust cover to get the rubber out. What lines?