91 Force 120 will not start

[oodlesiggy]

I had my boat out a week ago and it started right up, but would die a couple of times when I would throttle up but would run fine once I got going. Now I put it on the water started to throttle up and it died and would not restart. I changed the plugs, dumped the gas and started fresh, checked fuel filter. It would fire while spraying carb cleaner into the carburetor. Any ideas on what is wrong???

 

[oodlesiggy]

Re: 91 Force 120 will not start

I have also replaced a 3 batteries

 

[pnwboat]

Re: 91 Force 120 will not start

Maybe not getting any gas to the carburetors? Check your fuel lines for any deterioration. The check valve in the primer bulb can get stuck preventing fuel flow. Bad fuel pump diaphragm.

 

[foodfisher]

Re: 91 Force 120 will not start

Agreed, Runs when force fed fuel. Has to be the supply.

 

[Jiggz]

Re: 91 Force 120 will not start

One the best investment you can do is to install a see-through fuel filter between the discharge of the fuel pump and the inlet of the card. This will help you a lot on your troubleshooting. For example with your current situation if the fuel filter is empty you know the problem is upstream of the filter, i.e. fuel pump, check valve in the primer bulb, pick up tube or air leak. Or if the fuel filter is full of fuel and your engine is starved of fuel it will tell you the carbs got problems, i.e. clogged, or misadjusted floats.

 

[oodlesiggy]

Re: 91 Force 120 will not start

Ok I cleaned the carbs, and it's running like a champ out of water. I then took it to the lake and it started right up, but every time I put it in gear it dies. I took it back home and put the flushers back on it again ran great when in gear. Why would it be dying when I put it in the water?

 

[stubtail]

Re: 91 Force 120 will not start

Like PNW wrote: check your bulb, and replace the fuel pump diaphragm - not much money and easy to do.

 

[foodfisher]

Re: 91 Force 120 will not start

Ok I cleaned the carbs, and it's running like a champ out of water. I then took it to the lake and it started right up, but every time I put it in gear it dies. I took it back home and put the flushers back on it again ran great when in gear. Why would it be dying when I put it in the water?

Back pressure. Sounds like your idle rpms are too low.

 

[Jiggz]

Re: 91 Force 120 will not start

Ok I cleaned the carbs, and it's running like a champ out of water. I then took it to the lake and it started right up, but every time I put it in gear it dies. I took it back home and put the flushers back on it again ran great when in gear. Why would it be dying when I put it in the water?

At least two or three things things can cause this (assuming there is no misfiring). From the simplest one: Idle setting too low (on muffs it should be around 1000RPM~1100RPM) on water with gear engaged 700~800 RPM; Air-Fuel mixture screw (referred to as air screw) is improperly set. All carbs should at least have this set at 1~11/4 turn from lightly seated; and finally, exhaust leak either coming from the idle relief exhaust or from the exhaust manifold.

The exhaust leak can easily be detected while in the water only. The biggest indicator is the lower idling RPM while in the water compare when on the driveway with muffs, or when the cowl is off the engine idles perfectly but then struggles when the cowl is on while in the water.

 

[emoney]

Re: 91 Force 120 will not start

On a side note, I like to keep a clean fuel tank and new fuel lines on hand, that way, if I start experiencing any problems that could be tank/line/bulb related, it's easy to switch over to the temporary tank to verify. If it runs fine on the auxillary, then I've narrowed down the problem greatly. Don't know about where you live, but lots of yuck in this fuel in these parts. This Ethanol is eating up fuel lines (at least the older ones) like a dog that ain't been fed in two weeks.

 

[foodfisher]

Re: 91 Force 120 will not start

Back pressure. Sounds like your idle rpms are too low.

To expand, running on muffs the exhaust has an easy exit, out thru the snout (no pressure). Dunked in the lake, now the exhaust has to push the water out of the way to exit (back pressure). If idle rpms are correct the exhaust will exit out the idle relief ports. If the idle rpms are too low, when you shift into gear and the prop starts turning that's considerably more strain on an engine that's running too slow and it coughs/dies.