1986 force 125 running rough and no speed at high rpm

[sajeschwab]

Hi there im new to this site but you guys seem to know your stuff.

the issue im having on my 1986 force 125 (2 stroke, 4 cylinder) is that it was running really well on the river getting up to about 40mph at around 5500 rpm. But when I was out with it, it suddenly bogged down like it had run out of gas, which was not likely as there was still plenty of fuel. but I added some fuel anyway (around 10L which is nothing for the 100L tank) and she started right up allowing me to get back to shore.

on my way back to the boat ramp it was back to usual running great, then suddenly died again, except this time I got it started again without adding fuel, but as it was running, it was having sudden drops in power like all ignition was gone for a second. overall it was running like crap and it was running around 5000rpm while only going 10mph.

I had some stuff falling from my cowling that could of been sucked up into the carbs, which I thought was the issue, or maybe air in the fuel lines, but I have since rebuilt the carbs and added all new fuel lines as well as a fuel pump and spark plugs, and am still having an issue with it. if any one has any advice on what it could be let me know. thanks

by the way the psi in each cylinder is 140psi and the block is super clean for the age. thanks, saje.

 

[tg3690]

That stuff falling from your cowling is probably foam sound proofing material. As it deteriorates it gets sucked into your intake. I wouldn't run it again until all of that foam is removed. That foam has killed many a Chrysler/Force engine over the years.

 

[sajeschwab]

Yes it was the foam. I’ve since cleared all of the old foam out of the cowling. How can I get all of the foam out? After clearing the carbs isn’t it just the reed valves that just need cleaning? I’m also gonna put some seafoam through it.

 

[jerryjerry05]

The reeds are visible when the carbs are off.
Or get one of those snake cams for the new
style phones. $11 for my Android phone.

Test spark on each cylinder, and then do a
starting fluid test.
Start the motor, spray SF around the intake side of the
motor, under the coils and packs and the base of the
carbs. If this makes the motor run different?? then it's
sucking air somewhere.

 

[sajeschwab]

The reeds look good and I also used my air compressor to blow them out, and there is no air leaks. I’m almost certain the foam insulation from my cowling is what got into the motor. I also blew out the fuel lines, and am having the same issue. Scratching my head. Not sure what else it could be.

 

[sajeschwab]

Also getting a bit of backfire when starting in the beginning

 

[puffitu]

Check fuel pump diaphragm??

 

[sajeschwab]

The fuel pump is brand new as well as the diagram. The carbs are clean, the reed valves are clean. I’m thinking it’s getting the timing down pat and it will be good to go

 

[The Force power]

The fuel pump is brand new as well as the diagram. The carbs are clean, the reed valves are clean. I’m thinking it’s getting the timing down pat and it will be good to go

Sucking-up foam particles will not throw the timing off, have you checked the spark-jump with a tester? (as jerryjerry05 mentioned)

You may have intermittent spark on one OR more Cylinders, here's a link to diagnose the ignition-system ;

https://www.cdielectronics.com/wp-content/uploads/2016/05/Tech-Guide-Digital.pdf

 

[sajeschwab]

Awesome thanks. And no I was messing with the timing arm thinking the T on it was for throttle, not timing. I just set the timing and it’s running really well, but I won’t idle around 700-800 rpm. But if I throttle it around 1000-1200rpm it will run great. is the idle screw the one going to the block from the vertical shaft that's connected to the cam? and will messing with it mess with timing?

 

[Gearhard]

Not that this will solve your problem, but what size boat do you have the motor on? My '89 125 Force has issues getting much above 32mph, on an 18ft center console, about 1800Lbs of boat.

 

[sajeschwab]

I have it one a 19 foot Reinell that weighs around 1300 id say, the thing was getting over 40mph but since I sucked up the foam into the carbs and messed with timing it hasn't been the same. I got I running well now so it idles just fine, but when giving it gas it runs rough and doesn't seem to have any power, could be because of the fuel to air mixture but im not sure.

 

[jerryjerry05]

The rpm's at idle on the hose, 1200
In the water, in F gear at idle 750-800

IF???? nobody's messed with the timing it should be ok.
They won't jump time like a car motor would.

Yes the idle screw is at the bottom of the towershaft.
It won't change the timing if you adjust the idle.

The timing is adjusted by the screw/nuts on the end of the
timing arm. Make sure they are locked in place.

 

[puffitu]

Keep in mind that a piece of debris the size of a grain of sand can block the tiny fuel/air passages in those carbs. It happened to me; the cowl insulation deteriorated, I removed it ultimately but some of the crap somehow made its way into one of the carbs and rendered the needle from operating properly so ...

 

[sajeschwab]

Keep in mind that a piece of debris the size of a grain of sand can block the tiny fuel/air passages in those carbs. It happened to me; the cowl insulation deteriorated, I removed it ultimately but some of the crap somehow made its way into one of the carbs and rendered the needle from operating properly so ...

as I previously stated. the carbs and reed vales are fine. I cleaned them a while ago, they are now clean. I have to set the timing between my carbs, my cam, and the tower shaft (I think its called, it runs from the cam to the head) and have had no luck with any videos.