Merc I/O 140, Ongoing problem, HELP PLEASE!

[steve147]

Hello and thanks in advance for your time and help.
I've got an '89 VIP with the 140hp inboard GM 4/cyl engine. The problem which started late last summer:
Put it in the water, it starts/runs fine. Has a LITTLE hesitation upon throttle, but works.
After approx. 20 minutes or more of running both high and low speed, it will not accept any throttle to accelerate from idle, simply comes off idle, sputters and dies.
From idle, no matter what you do it'll die. Slow feed of throttle or jam it, sputter, sputter, dead.
At first signs of trouble it will idle fine while not in gear, only die when you put it in gear, then it gets to where you have to give it throttle just to start it, drop it back to neutral, and then TRY putting in gear, only for it to die again.
As I said, it started this last outing last year.
I Just rebuilt the carburetor with new accelerator pump, the whole works, new alternator, filled it with new premium gas and Sea Foam, replaced and gapped the points, checked the 2 year old spark plugs which still look new, and last year I once again replaced the ignition coil and and added an external resistor (it seems to burn up coils...).
HELP PLEASE?!?
THanks, Steve W.

 

[cooter2506]

Re: Merc I/O 140, Ongoing problem, HELP PLEASE!

Sounds like a fuel delivery problem. Run it on an auxillary tank. If it still does it then we know its engine side if it runs good no problems then it is tank side. Does it have a water/fuel sepperator filter on it?

 

[steve147]

Re: Merc I/O 140, Ongoing problem, HELP PLEASE!

Sounds like a fuel delivery problem. Run it on an auxillary tank. If it still does it then we know its engine side if it runs good no problems then it is tank side. Does it have a water/fuel sepperator filter on it?
__________________
It's got a "cone" shaped thing on the fuel pump, or right next to it. Is this the separator?
The fuel pump is hard piped to the fuel tank, how would I go about trying an auxilliary fuel tank?
Thanks, Steve W.

 

[Bondo]

Re: Merc I/O 140, Ongoing problem, HELP PLEASE!

It's got a "cone" shaped thing on the fuel pump, or right next to it. Is this the separator?
The fuel pump is hard piped to the fuel tank, how would I go about trying an auxilliary fuel tank?

Ayuh,... That's just a Filter,...
You should plumb in a cannister type spin-on water seperating filter too,...
Just Before(Upstream) of that 1...

At the inlet of the fuelpump is a good place to plumb in a test tank...

 

[jimsheila1996]

Re: Merc I/O 140, Ongoing problem, HELP PLEASE!

I had a Searay Seville with that engine that had similar issues.

It drove us mad as you say, fire it up run out in the lake a ways then begins to act up. I bought coils, points, rotors plugs wires fuel filters, rebuilt carb and on and on.

It sounds wierd but check the advance mechanism for the distributor BOTH the weights and check that the distributor itself rotates as it should a bit and springs back (maybe 1/8 turn.

It might not be your problem but it's worth a look.

We finally figured it out after we'd bought another boat. It has worked fine since as I see the people who bought it all the time.

 

[steve147]

Re: Merc I/O 140, Ongoing problem, HELP PLEASE!

I checked and oiled-up the cetrifugal advance, it seems fine.
Also checked the fuel filter on the pump and the hoses and check valve and vent on the tank, all seemed OK except the filter and hoses seemed to have very little fuel in them upon disassembly, some, but NOT full...
Took the fuel pump off, seems to work by hand, and no fuel in the lower vent housing, I'm gonna try to rig-up a fuel pressure gauge and check that out before I try the auxilliary tank idea and actually go back out on the lake. I HATE being pulled in!
Any other ideas?
Thanks, Steve W.

 

[jimsheila1996]

Re: Merc I/O 140, Ongoing problem, HELP PLEASE!

Just in case you didn't but it sounds like you did. When you oiled up the advance, could you grab the rotor and twist it maybe 1/10 turn against the spring? That was really the root of my problem that shaft was set up even though the weights could move it was only 1/2 working.....I will shut up now

 

[steve147]

Re: Merc I/O 140, Ongoing problem, HELP PLEASE!

Yup, the distributor shaft will turn by hand and snap right back, so I don't think it's the advance mechanism.
I'm gonna put a fuel pressure gauge on it tomorrow and check the pump pressure. I just removed the fuel gauge from the tank so I could see in there, and the dip tube is solid metal and not damaged or restricted, so I think the tank's fine.

 

[fishrdan]

Re: Merc I/O 140, Ongoing problem, HELP PLEASE!

Check the fuel hose from the tank to fuel pump, make sure all the clamps are tight and the hose isn't cracked/split. I had problems like this on my old boat and it turned out to be a small crack in the rubber fuel hose at the tank fitting, it wouldn't leak fuel, but would suck air.

When this is happening, pop the top off the carb and see how much fuel is in the bowl. Is the float adjusted correctly and was the carb's fuel filter replaced?

Is this problem related to only to shifting into gear,,, or all the time; in neutral, going into gear, while in gear.




Did you set the dwell when you replaced the points, or just gap them?