Need help - Mechanic can’t replicate issue

[DuckHntr479]

i have a 60 HP Mercury (2002ish) on my duck boat. Boat the boat and motor used from my uncle. He said he never had any problems and I have no reason not to believe him. The last three seasons, it’s given me fits! I’ve had it to two different shops and the last one twice. The last time I told them to keep it and run it on the water (their shop is on the lake). None of them could replicate the problem and simply cleaned the carb except for the last time.

Whether I’m fishing or hunting, it always runs like a champ going out but on the return trip 9 out of 10 times it looses all power. Never dies but sometimes back at the ramp if I kill it it’ll be hard to get it to start. Always cranks right up when I go out first though, even in sub freezing temps duck hunting.

I don’t know much about boats but it seems like it’s either flooding or fuel starved to me. When I throttle up, it starts to accelerate but then dies back. I can let off the throttle a lot and it runs pretty normal at that throttle level but if I try to throttle it up, it acts bogged down like it struggling under a load or something.

I took some videos today when I put it in for my preseason (duck season) check but can’t seem to upload them.

Any advice? I’d love to get it running smoothly before this duck season!

Thanks so much!

 

[roscoe]

Welcome to iboats.

Get a fuel pump rebuild kit from a merc dealer and instal it, $22, 30 minutes.
If the diaphragm inside is leaking internally, it will flood the crankcase as you described.
Let it sit over nite, and it fixes itself.

About 90% of the time, this will fix the problem.

 

[jimmbo]

Seems the problem occurs after a hot soak. Electronics can be heat sensitive, but so can the garbage that is marketed as Gasoline these days. It could be vapour locking(fuel starving) upstream of the fuel pump, or the fuel could be absorbing heat while trapped in the fuel hose between the fuel pump and carb(s), and when the inlet valve the carb open to let in fuel, the fuel being warm will flash/boil and flood the carb, either condition can be caused by a fuel with a low vapour point. Since most engines are FI these days and are less prone to either condition, some refiners have taken to cutting costs/increasing margins by selling fuels less resistant to flashing.

 

[Nauticaljim]

Did you solve the issue?

 

[DuckHntr479]

Roscoe, thanks.

Jimmbo, I don’t believe it is a temperature related issue because when I duck hunt, I’ll run it 15-20 min out to the blind and then it’ll sit for 4+ hours in the cold with plenty of time to cool off. And then when we’re headinf back to the ramp is when it will do this. Seems to be logical what Roscoe says as a possibility if the running it out is flooding it and then it isn’t sitting long enough for the fuel to evaporate. It smokes a lot once it starts acting like this too so that tells me something is going on with the fuel, fuel mix, or how it’s burning it. I do use Stabil in each tank of gas and occasionally run Seafoam through it. Is there a conditioner I can add that would resolve flash boiling you mentioned in case that is it or there something I need to check within the cooling system? I’m ready for a shotgun approach to fixing this.

Nauticaljim, not resolved yet. I just posted last night. Thanks!