2.5 Runs then quits after an hour

[broncobill]

I have a 1986 Renken 16 1/6" open bow with the 2.5 OMC I/O.
We took he boat out this pass Sunday and it was running good. Would idle good and pull a tube good.
Then about an hour to an hour and a half later, it would bog down, then run good and back and forth for a little bit.
Then it would not idle at all. I could get it started but not for very long.
Then it would not start at all. The fuel filter was about half full.
The following day, I pulled all 4 plugs. Looked good, dark brown and dry. Rotor and cap looked good too.
Put the muffs on the outdrive and it started right up. I let it idle for about 10 minutes, turned it off and it started right back up.
This is the first time I've had it out this year.
The last time I had it out last year, it did something very similar. I thought I had hit switch for the fuel pump. But now I don't think so.
What could possible wrong?

 

[alldodge]

The fuel filter was about half full.

If this is a canister filter, then you have a weak pump, an air leak or a restriction.

 

[broncobill]

It's a see thru in line filter.
Should the filter be completely full?

 

[alldodge]

It's a see thru in line filter.
Should the filter be completely full?

Oh that's bad news, not that it keeps the engine from running, but its a hazard on a boat and not allowed by USCG regs.

Being half full is normal for those type filters.

I'm thinking you have a fuel issue. Its either the carb, fuel pump, filter or a restriction. Restrictions come from filters, collapsing fuel line, anti-siphon valve. The fuel pump should output 4 to 7 psi at all rpms. At least with the inline filter it would be easy to install a pressure gauge to check.

Does you fuel pump look like the one in this link
http://www.mercruiserparts.com/bam/subassembly/30903/963/110

 

[broncobill]

It has an electric fuel pump on it. I replaced it last year too.
I'm guessing I need to put a metal fuel filter on it.
Last night the engine fired right up. Ran it for 15-20 minutes at different rpm's with no issues.
When the engine died on me in the middle of the lake, the filter was at least half full. So the carb should be the issue?

 

[jerryjerry05]

The tank vent line could be clogged??
​Ethanol?? if so the E could be messing with the hoses and causing them to collapse??

The electric fuel pump isn't usually a good idea unless you have an oil pressure switch and a setup like the newer motors have.
They don't know if the motors running and if the motor stalls they continue to run and can fill your motor with gas and other problems..BOOOOM!!

 

[alldodge]

My guess is you current filter is between the pump and carb. If this is the case, your pump may be clogged up. Check the anti-siphon valve at the tank. Its the barbed fitting the that the fuel line is attached to

I would install a canister fuel filter so you can use the standard spin on fuel filter. Keep the fuel filter even with the tank output fitting.

 

[broncobill]

Yes, the filter is between the pump and carb. If the pump was clogged, wouldn't the engine empty the fuel filter?

 

[alldodge]

Yes, the filter is between the pump and carb. If the pump was clogged, wouldn't the engine empty the fuel filter?

The motor sucks the fuel out of the carb from the jets in the base of it, but cannot do the same from the fuel line its on top the carb.

I just thing its a fuel problem so I would look at everything, including any rubber fuel line. Older rubber line and collapse in side and show no signs on the outside. The type A1 fuel line has better properties to stop this then the older type, and currently only one which is USCG approved for boats

 

[broncobill]

I will replace all fuel lines and filter. Before I hook the line back up to the carb, I'll make sure the pump is working. I may even put a filter between tank and pump. If this does not solve the issue, I'll have to rebuild the carb.
Thanks for the help.

 

[alldodge]

I may even put a filter between tank and pump.
.

You welcome

and the filter is there to protect the pump and carb, and it should be before the pump