3.0l OMC stalling at WOT

[greasemonkey1985]

My brother and I have a 1986 thundercraft that was bogging out at WOT but is now getting up to plane then stalling out, it will surge a little then stall, start right back up, cruise at slow speed but will stall out at WOT. we have replaced fuel pump(electric) and checked all lines, replaced anti syphon valve, drained out all the gas and replaced with new gas, checked and cleaned carburator, replaced coil, checked points(replaced by previous owner at beginning of season) seems like rotor moves free for timing advance, not too sure what else to check. It seems that the more we fixed fuel problems, the worse the problem got. Someone had mentioned ESA (or something like that) anyone help with checking, or bypassing to verify the problem or have any suggestions on what next??

 

[futz]

Re: 3.0l OMC stalling at WOT

86' did not have a electric fuel pump. i don't know even on a 2009 3.0 merc if it has a electric fuel pump.

I don't think omc ever put a electric fuel pump on a 3.0 i don't think so.

How it is getting power i don't know. The electric fuel pump giving you 4-6 psi no less and for sure no more then 7 psi, it will overpower the needle and seat.

That alone will not let the motor run, and flood out the carb.

Ok on the water with a driver, you disconnect the esa module, it is connected to the micro switch, on the shift converter, it is the little plug with the spring clip. There maybe 2 spring clip module plugs one is for the overstroke switch, disconnect that one also.

So when your in gear going already about 10 mph unplug the esa.

Now be aware there are 2 / 50 amp fuses in holders also with spring clips, they pass thru a plate, don't disconnect those.

post the result we will go from there.

 

[greasemonkey1985]

Re: 3.0l OMC stalling at WOT

thanks, the boat came with the electric fuel pump already installed and ran great for 2 runs, once when we bought it and for about 30 minutes of our first run which we really gave the boat a hard run. We were hopping some nice waves and a couple of times the prop even came out of the water(not on puropose) would that cause any problems or anything else to look into?? but I will check the module the way you said,

 

[futz]

Re: 3.0l OMC stalling at WOT

What kind of fuel pump is it, just a auto one and the fuel boss where the mechanical one is supposed to be has a plate blocking it off?

I don't know even if the boat is safe. You ever get boarded bye the coast guard you could get a ticket or towed in.

You could get blown up and i am serious.

Where is power getting takin from for the pump?

They hook it to the keyswitch? That is a big no, no.

That previous owner, could be held liable for selling you a unsafe boat.

If it's a marina i would bring it to them, and have them install the correct pump, the right way.

So where is the overflow tube that comes from the carb go. or did they block it off with a plug, see overflow from the carb is supposed to flow back to the fuel pump. And not in the bilge so a pool of gas can form, and blow you and everyone within 50 feet up.

 

[greasemonkey1985]

Re: 3.0l OMC stalling at WOT

ok, I will look into that, I didnt realize that it was that big of a deal but I do see what you are saying and look into it. Honestly I thought that the electric pump would be fine and less problems than a normal pump. I will look into it, Thanks.
I looked at the ESA and whoever wired up the fuel pump, shared the ground with the ESA and moved the spacer from behind the ESA to the other side where the nut is and pinched the wires almost flat. It actualy made an indent into the ESA where the wires are, there are no bare or broken wires but I assume the insulation is no good when 4 wires are squished together that close and that thin. We just ordered an module and due to noone having time to go out and test it I will hope for the best,
I will check out the fuel pump stuff and see what I can do, Thanks again

 

[greasemonkey1985]

Re: 3.0l OMC stalling at WOT

Now, I just talked to my brother and he said that the float is what stops the fuel pressure and that the pump doesnt run over 7 psi, alot of the boats that he looked at had electric pumps, where would I look or go to see if this is a problem. Not to sure where you are from, I am in Ontario Canada and maybe some rules are different, I do see your point about not pooling fuel in the bilge(i assume bottom of boat near drain plug) but there is never a gas smell before or after starting or running the boat.

 

[futz]

Re: 3.0l OMC stalling at WOT

good luck just let me know when your boaing near me so i won't be there.

 

[Daviet]

Re: 3.0l OMC stalling at WOT

I agree, there should not be an electric fuel pump in your boat. Know to the WOT problem, get a can of aerosol carb cleaner, when problem starts spray THROUGH flame arrestor. If engine picks up and gains RPM you have a fuel problem, carb most likely.

 

[tpl71bug]

Re: 3.0l OMC stalling at WOT

I have a 88 omc GM 5.0 with same problem at wot i been chasing all summer please post if you figure anything out im going to also check my esa this weekend ! FUTZ after esa is unpluged should i throttle up . i have a few other threads bookmarked on how to check it. id like to get all the knowledge i can thanx

 

[futz]

Re: 3.0l OMC stalling at WOT

yes unplug the esa at say 10 mph and then run it wot see if the problem goes away.

See if you can get the motor to idle around 500-550. then you can try it without the esa for a while.

 

[tpl71bug]

Re: 3.0l OMC stalling at WOT

Well had boat out this weekend and when it started cutting out on me i unpluged the esa. It stalld out on me once more but i could smell fuel in exhaust ,so i think there is also a small fuel problem . but after unpluging esa it did run much better . i would just shut down the motor before pulling it out of gear . i plan on ordering a new esa for next year . i m only gonna make it to lake maybe twice for the rest of the year , i live in pa its a short season .thanks for your help futz