Force 97 Model 75HP - Will run at Fast Idle but that's it

[rwhisenant]

Motor will start with Fast Idle on. When you pull control back to take put it in gear the motor goes dead. It starts very easily and will run as long as you leave it on fast idle. Any suggestions would be greatly appreciated. This is a project boat, and I want to make sure I've covered all the bases before I take it in for service.

 

[pnwboat]

Re: Force 97 Model 75HP - Will run at Fast Idle but that's it

Have you done any basic maintenance? Plug wires, spark plugs, fuel pump diaphragm, etc?

 

[rwhisenant]

Re: Force 97 Model 75HP - Will run at Fast Idle but that's it

I haven't at this point. We had to put a new starter on the motor, but it ran like a dream till the last time we went out. When we were idling back into the dock it quit and we couldn't get it re-started. Then the next day we tried to start, and got to where we are now.

 

[pnwboat]

Re: Force 97 Model 75HP - Will run at Fast Idle but that's it

Taking it in for service might be a OK if you have a lot of extra cash on hand. First thing to do is a compression check. If compression checks out OK (approx. 120LBS in each cylinder), then if you haven't replaced the fuel pump diaphragm, that's a good place to start. They should be changed on a regular basis and are relatively cheap (about $12). The other thing to check is the reed valves. That's a little more involved and more expensive. Reed block assy's are about $70 each + associated gaskets. There are three of them on your motor. If you have a broken reed petal, you only have to replace the broken one, not all three. Late 1990's model Mercury/Force motors are known for breaking or cracking reed valves.

 

[rwhisenant]

Re: Force 97 Model 75HP - Will run at Fast Idle but that's it

OK. Here is what I've done. Replaced plugs, rebuilt fuel pump diaphragm, tried to run fuel treatment through it. It is the craziest thing. It runs perfectly at fast idle as long as you keep it over 3,000 rpm's. If you let it get below that ie... move it back so you can put it in gear it goes dead very quickly.

Any more suggestions, it's driving me crazy.

 

[Frank Acampora]

Re: Force 97 Model 75HP - Will run at Fast Idle but that's it

You also need to check the stator and CD box. I'm not sure about that particular engine, but it has Merc electronics. SOME Merc ignition systems used a dual ignition mode: One part for low speed and one for high speed. If yours IS like this and the low speed portion failed, It will start and run fast, but die at low RPM.

 

[foodfisher]

Re: Force 97 Model 75HP - Will run at Fast Idle but that's it

Does it have a neutral safety switch that may need adjustment?