A poorly Force 85 - beats me!

[Craig cK]

Right here goes:<br /><br />Just bought a boat with an 85hp Force engine (89 I think)<br />It runs; but back back fires loads. Discoveries and experiments so far:<br />I have a sprak at all plugs<br />I've swapped coils around for different cylinders and still have the problem.<br />No. 2 plug always fowls up black<br />I've stripped and cleaned all carbs.<br /><br />That's about it so far!<br /><br />I'm currently guessing it could be the stator under the flywheel?<br /><br />All help very very much appreciated! The engine is otherwise in very good condition!

 

[rodbolt]

Re: A poorly Force 85 - beats me!

what color are the coils? what color is the motor? have you checked the fuel pump diaphram and cleaned the puddle drain system? is the timing link to throttle tower adjusted properly? have you ever seen the motor run correctly? if so what transpired from correct running to poor running?

 

[WillyBWright]

Re: A poorly Force 85 - beats me!

The stator makes electricity for charging the battery and powering the ignition system. If even one cylinder is getting good spark, the stator is probably good. The middle sparkplug turning black is what needs to be eoncentrated on. Broken or leaking reeds usually leave a cleaner plug than the rest, but could make it blacker. Spark wouldn't cause blackness unless it was way off time. If the other two are on time, then all are. Weak or no spark would leave a cleaner plug.<br /><br />Make sure the throttle butterflies are synchronized, but I'm betting on a bum fuel pump. It takes pulses from the crankcase to push on a diaphragm. Those have two-stage pumps and are driven from two different cylinders. Methinks you have a bad gasket or a torn diaphragm in the fuel pump. Rebuild kits are cheap. I'd start there After a compression test. That's always first.

 

[Craig cK]

Re: A poorly Force 85 - beats me!

Wow! Thanks for the prompt responses!<br /><br />I forgot to list those two things!<br /><br />checked the fuel pump diaghragm - all looks good.<br />Compression was similar between all cylinders.<br /><br />I've heard of this spill / puddle drain system - what is it and where do I service it?<br /><br />It seams to run better with No. 2 plug cap off - smoother without the back - fires.<br /><br />The motor (block) is black and the cowling a charcoal colour. The coils are blue.<br /><br />Timing link to the throttle tower? All butterflies are opening evenly.<br /><br />Not seen it run right - bought at an auction! Wouldn't start on the day!<br /><br />Thanks ever so much for the help gents! You're stars!

 

[Craig cK]

Re: A poorly Force 85 - beats me!

A few more thoughts.....<br /><br />It will not tick over, but what tickover there is seems high (unsure)<br />The throttle linkage cam does not engage with the black roller when hand throttle is given - is that normal? <br />Mixture screws are all about 3/4 of a turn out<br /> would it be worth making No. 2 leaner?<br /><br />I pressume it's screw in for leaner?

 

[Craig cK]

Re: A poorly Force 85 - beats me!

yup...she ticks over with no 2 plug cap off; but back fires to a halt with it connected.<br /><br />Do you think I should strip that fuel pump again?

 

[chuckz]

Re: A poorly Force 85 - beats me!

Check the center carburator for a hung up float or a broken reed.

 

[Craig cK]

Re: A poorly Force 85 - beats me!

The floats ok, I'v checked that...will go look for a broken reed....thanks!

 

[Craig cK]

Re: A poorly Force 85 - beats me!

Nope.....the reeds are ok! (or seem to be) Looked in through carb and pressed with screw driver - resistance felt on all.

 

[Craig cK]

Re: A poorly Force 85 - beats me!

Oh, don't leave me alone on this one!

 

[Craig cK]

Re: A poorly Force 85 - beats me!

Could it not be a duff power pack? Just an idea! Clutching at straws as one could say!

 

[eurolarva]

Re: A poorly Force 85 - beats me!

NIne bucks will get you a rebuild kit for that fuel pump. The diaphram may look good but could be stretched or dried out from ethynol. Check the fuel valves closely. Two are press fit. Verify that the springs work in them and that the gaskets arent broken. The press fit ones are almost impossible to get out without breaking them. Mercury sells the fuel valves for about 5 bucks a piece and the gaskets for them for half a buck.<br /><br />Is back fire coming out the carb or out the exhaust?

 

[Craig cK]

Re: A poorly Force 85 - beats me!

Many thanks! <br />The backfire is out of the exhaust.<br />I'll strip that fuel pump again then!<br />I've seen advertised a similar engine, so I think this may be the best route - especialy if their hydraulic ram is good.<br />Would be nice to have this one running though - she looks very clean and unused and very lttle corrosion.<br />I'll keep you posted!.....

 

[Craig cK]

Re: A poorly Force 85 - beats me!

Fuel pump.....<br /><br />Should it look like this?<br /><br />Is that diaghragm too stretched?<br /><br />damn! can't upload pictures!

 

[OBJ]

Re: A poorly Force 85 - beats me!

Craig....just a thing to try...<br /><br />Pull each spark plug and bring each cylinder up to top dead center....you can use a screw driver to feel the rise of the piston. Then mark the flywheel at the timing pointer which cylindr it is. With a timing light on one spark plug lead at a time, crank the engine and see it the numbers on the flywheel match the cylinder the timing light is on. This indexing will tell you if the spark is on the right cylinder.

 

[Craig cK]

Re: A poorly Force 85 - beats me!

Thanks OBJ! I did actually try every combination of plug caps incase! (dare I admit that!)<br /><br />I've just fixed it! I'm so so so happy!<br /><br />I've just re-built the fuel pump with liberal amounts of silicone grease and she's a beaut now! All I need to do is invest in a seal kit and I have myself a screamer! so so happy! <br /><br />I had made an appointment to view another similar engine tonight! Just found this in time!<br /><br />I'm pondering if the other engine may have the same problem - the guy said it's running really smokey - I recon it must be a common fault with neglected engines????<br /><br />I sent a piccy to WillyBWright of the fuel pump diaghragm and he thought it looked stretched so fingers crossed for a trouble free season! <br /><br />Thank you everybody for all your help! Think I owe you all a round!

 

[bnk999]

Re: A poorly Force 85 - beats me!

My Chrysler 75hp was running poorly and it would only run with the cover off -- turned out to be a stretched out fuel pump diaphragm-- Easy to fix -- a little hard to diagnose