mercury keeps fading

[barrashee]

I've got a 1997 115 hp 2 stroke mercury. Came with the boat, so new to me. It will run fine at 5,000 rpm for about 5 minutes then begin to bog down as if starving for fuel. If I throttle back to idle for a bit I can rev up again for a short time, then its repeat the procedure. This problem is worse coming back than going out, so I'm wondering if its heat related. Engine will work for hours at a slow pace for trolling. Ideas?

 

[KJM]

I've got a 1997 115 hp 2 stroke mercury. Came with the boat, so new to me. It will run fine at 5,000 rpm for about 5 minutes then begin to bog down as if starving for fuel. If I throttle back to idle for a bit I can rev up again for a short time, then its repeat the procedure. This problem is worse coming back than going out, so I'm wondering if its heat related. Engine will work for hours at a slow pace for trolling. Ideas?

Is the gas tank venting properly?

 

[racerone]

Tested the overheat horn ??-----Installed a new impeller when you got the boat ??-----Inspected / cleaned the carburetors ?----If unit sat for years the carburetors could be gummed up.

 

[barrashee]

Tested the overheat horn ??-----Installed a new impeller when you got the boat ??-----Inspected / cleaned the carburetors ?----If unit sat for years the carburetors could be gummed up.

thanks for that. I did have the carbs cleaned because I got some bad gas. Also got rid of that old gas. Runs a lot better since carbs cleaned but still has the aforementioned problem. I took to dealer, they couldn't get leg off to check the impeller. Where iss the overheat horn? Also in leg? Oh, no horn sounds , the engine just bogs down. Or are you suggesting the engine IS in fact overheating but the horn is failing to sound? That would make sense.

 

[barrashee]

Is the gas tank venting properly?

yeah, we checked that. Also dropped the vacuum created from 8 to 4.

 

[racerone]

Find another shop to get a new impeller installed.----Have them test your over heat horn !

 

[Dukedog]

when it starts losing power push tha key in.. also try pumping tha bulb under same scenario.... if that changes anything then ya may have a mechanical fuel pump or blub problem.....

 

[Chris1956]

A shop could not get the gearcase off? That's a new joke, right? If no joke, you need a new shop.


Overheat alarm sensor is on the cylinder head. The sensor should ground when it detects overheat. The overheat alarm should have power to it when the ign key is on. The other side of the overheat alarm is connected to the overheat sensor, so when it grounds, the horn will sound. You might ground the overheat sensor and see if the alarm sounds.

 

[barrashee]

WOOT! solved the problem. Someone suggested it was blockage on the mesh filtere of the fuel pick up . I pumped fduel bacxk through the fuel line to the water separator. Now runs fine for 20 minutes, at which point I was satisfied and stopped the test. Thanks to all who contributed good ideas. And hold this as another idea to suggest next time

 

[tphoyt]

That’s great news but what about that water pump? When’s the last time it was done?