98 90 HP Force by Mercury Marine, won't stay running

[dbmacboat]

Hey guys, hoping to get some insight. My 90 hp Force was turning over but not starting/firing. Primer bulb was a little soft and I had a new one so replaced it. I put some new plugs in just to be sure. Hooked her up to some water in the back yard and she started and ran, throttled high and low, idled, shut it off and came back in an hour, started again, ran fine again.

Got her out to the lake and it started once in the water, stalled out and couldn't get it to fire so back to where I started. Again, the starter cranks the engine but the engine won't fire.The gas is good (new), as is the gas/oil mixture ratio at 50:1. When I pulled the plugs they were wet with fuel so it seems to be getting fuel to cylinders.

Not sure where to go from here. Anybody have any suggestions?

Any help is much appreciated!

Thanks,

Dennis

 

[jerryjerry05]

Do a compression and spark test.
Then start with the fuel system.
Check all the hoses for soft / mushy hoses.
Check the pump diaphragm and check valves.
The 98 has an enricher for a choke.
Unhook it and see if it's working right.
Turn the key and push in and see if it's pumping.

 

[dbmacboat]

Thanks jerryjerry05! I took it in to a mechanic, he pumped the heck out of the primer bulb, it started and ran without fail, throttled up and down, idled, shut off and re-started without fail! Thought that I had squeezed the bulb enough, guess not. Guess I'll try it at the lake again. might still be a problem, if so, maybe air getting in through suction hoses from tank to fuel pump? Hose clamps?
Thanks again!

 

[Jiggz]

The best thing you can do now in addition to what Jerry's suggested is to buy a clear fuel filter and install it between the fuel pump outlet and the carb's inlet. Even a G2 type from (Walmart) will do and it costs less than $5. During testing, make sure you prime the fuel so that the clear fuel filter should be at least 3/4 full (because of initial air in the filter, even at 1/2 full will do as long as the primer bulb becomes firm). Now do a test run. The clear fuel filter should stay at least 3/4 full at all times. If not, you have fuel delivery problem, leaky fuel hoses, faulty fuel pump, restricted pick up, faulty primer bulb check valves, restricted tank vent, etc.

If it stays full (clear fuel filter), and the engine is still not running well, it means you could have carburetor or electrical problems. If the motor seems to run fine while on the driveway but will not even start or idle while in the water, it could be an indication of leaky exhaust. To test for this, try using a trash can to submerge the lower unit (up to the cavitation plate) while testing at the driveway (just make sure the cowl cover is on at all times). In this case, you are simulating running the motor at the lake. If motor will not run or idle in this setup (unless you take the cowl cover off) there is a good indication you have exhaust leaks. The exhaust is being recirculated back into the carbs starving the motor of fresh air, thus cannot run properly.