'96 Evinrude 25hp - kills at trolling speed

[BoxMN]

Have '96 rude 25hp 2-stroke. Last year was fine. This year it started acting as if the bulb has leak - need to pump it up after sitting just a min or two. Also won't troll at idle, it will slowly lose rpm and kill unless you goose it a bit. At higher than idle it will troll for extended periods.

I replaced the fuel line and bulb, but reused the same fittings (good tight hose clamps). Still same thing. It sure seems like it has an air leak. Could the gas tank filler cap be leaking?

I did not change plugs this spring, could bad/old plugs do this? At slightly higher rpms no killing at all, and it starts a bit hard and needs lots of choke even when warm.

Thanks for any advice.

[marine_man]

The gas tank filler cap shouldn't make any difference - the tanks are open to vent, unless you're not opening the vent on it.

Follow the fuel hose all the way to the pump - any leaks when you pump the bulb up?

I'm guessing that it's not a leak, given that it runs fine at higher speeds. It might be time for a fuel pump rebuild.

marine_man

[BoxMN]

Thanks. There is no vent on the tank, like on our merc tank. I just screw the cap back on tight after filling up, and off we go. I am not supposed to losen the cap am I? I always thought Mercs you needed it vented, and OMC were closed tanks, no?...

No visible leaks anywhere. Is the fuel pump rebuild doable on the water? Is there a kit I can buy? I think it is just that little diaphragm right?... or not...? I am not a mech, but not afraid to tear into it

Thanks!

[Surface Tension]

The tank might not have a vent screw but theres a spring loaded vent. If your certain theres no air leak in the fuel line then I agree with the fuel pump. I dirty carb, namely, the low speed end will do that but you said you had to keep pumping the bulb up.

Its a simple diaphragm pump.

[boatfixer]

Those have some pretty small passages in the low speed circuit of the carb. Doesn't take much to obstruct gas flow. I'd look at a good cleaning and rebuild of the carb. As the other mentioned, rebuilding the fuel pump is an easy fix as well.

[riverrat56]

I had a '91 40hp Evinrude do the same thing, had the carbs cleaned and bingo, she runs like a champ.

[BoxMN]

Thanks all. Looks like I might wait till fall, then do a little cleaning while it is on shore.

[Maverick]

I would replace the connections on the gas line at the tank and at the motor. I had a similar problem and it turned out to be the O ring in one of the connections.

[MWellner]

I used to have a 95 Evinrude 25hp with the same problem, it would bog down and then rev up. Turned out to be a crack in a plastic fitting on the gas tank, too much air was getting in.