85'115 hp Merc bogs down

[bigdogbalog]

The following has been done: Compression-good all cylinders. New stator installed and 2 new switch boxes. Carbuerators cleaned. Fuel pump rebuilt. New fuel lines and connectors installed, including bulb. Good spark when checked at all 6 cyl. Engine starts good and runs good at low speed. Will come up on plane and run great for about 5 minutes then just drops off and will not pickup again. Mechanic is pulling his hair out and I NEED to go fishing. Please help!!!

 

[LubeDude]

Re: 85'115 hp Merc bogs down

Fuel tank vent not open or plugged???

 

[mellowyellow]

Re: 85'115 hp Merc bogs down

i'd guess fuel starvation as well... check the<br />simple stuff first, like the gasket on the quick<br />connect, fuel lines/connections etc.<br />primer bulb stay firm when it happens?

 

[2cycle]

Re: 85'115 hp Merc bogs down

If you happen to have a built in tank check the anti-siphon valve (if it has one). I have a 74 150 and had similar troubles until I removed the anti-siphon valve and replaced it with a regular barb fitting. Like you, I had gone all the way through the fuel system only to find that this was the problem. The valve was new, however the fuel pump could not generate enough suction at WOT to keep running for sustained periods. If you have the built in tank, first try running it with a portable tank first and see if the problem goes away (just make sure the tank is vented). If so, you know where the problem is.

 

[bigdogbalog]

Re: 85'115 hp Merc bogs down

I should have told you, the mechanic was running the motor on a new 6 gal. tank and not on the built in tank, or he may have used his portable tank. I asked him if he used the main tank and he said no.

 

[vista4u2]

Re: 85'115 hp Merc bogs down

Sounds to me like what ever tank you are using isn't venting properly.

 

[bigdogbalog]

Re: 85'115 hp Merc bogs down

the mechanic was using his portable tank and fuel line. says the bulb stays hard.

 

[bigdogbalog]

Re: 85'115 hp Merc bogs down

found the problem finally. high speed coil in the stator was bad. this was a new stator which had been replaced early on. this was a bad new one!! thanks to all for the replies and help. even a bad day on the water is better than a good day at work.