1986 Force 125 Low Speed/Low RPM Problem

glachiew

Cadet
Joined
Jun 27, 2011
Messages
7
BACKGROUND INFO: I am the second owner of this engine. I bought it from a friend who had it stored in his barn for ten years. It's always had problems running at low RPMs (or idling for long periods (more than 1 or 2 minutes). It cut out on me last week on a very windy day. I had to beach it and then the wind switched and the stern swamped. Took two days before it could be recovered by the rangers. I mucked the boat out this weekend, dumped all the gas (had water in the tank from the breather vent) and threw in 6 gallons of new fuel. I replaced the fuel line and primer ball earlier this year and all the hose clamps are the screw type. Additionally my tach is not hooked up because the motor is now mounted on a different boat with mismatched gauges in the dash (next years project). But the engine RPM's "sound" fine, well within normal range IMO.

THE PROBLEM ON THE WATER: I fired it up on Saturday and let it idle for a couple of minutes at the dock. When it began to stumble I had my friend squeeze the primer ball and that helped it to recover. We ran across the lake at a good speed (30mph) with no further problems. When I fired it up again to make a move it started just fine, began to move, then bogged down. My friend primed it again (squeezed the ball) and we were off and running again. If I repositioned the boat after a drift at low speeds, it kept needing to be primed (2 or 3 squeezes to get into postion). But, if I wanted to move across the lake and get it to a high speed (say more than 10-15mph) it was just fine after one squeeze.

THE QUESTION: I've read a couple of threads about similar problems with idling and some of the conclusions were clogged intake jets on the carb. I've thought that possibly the diaphragm was shot after sitting in the barn for ten years and would just replace either it or the fuel pump. There is no inline fuel filter that I can see. Is it worth just going after the fuel filter to start or should I start with something simpler?

Thanks for your sage advice!
 

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,842
Re: 1986 Force 125 Low Speed/Low RPM Problem

IMO, any motor that has been sitting for that long, needs to have the carbs rebuilt.

Also, rebuild the fuel pump.

Replace any fuel lines and clamps that have not been replaced. Especially the ones from the fuel pump to the carbs.


Last but not least, idling is greatly effected by the fuel recirculation system. This system takes unburned fuel from the crankcase, and tries to re-use it by routing it back into the fuel system. Cleaning it out is a real pain, but may need to be done.
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: 1986 Force 125 Low Speed/Low RPM Problem

Like roscoe said: After sitting that long, you should assume that all wearable parts need replacement and the carbs are varnished. So: remove the carbs, disassemble them and clean well (I like WD 40 as a cleaner) replace the diaphragm and gasket on the fuel pump, change the fuel lines, ADD an inline filter between the pump and carbs, and clean the screen under the black plastic fuel inlet to the pump.

If the engine has a quick-connect in the fuel line, remove it and clean both male and female fittings.

And by the way, it would be a good idea to change the lower unit oil and water pump impeller too.
 
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