85hp Force - Backfire? - w/ video

[devl]

Please take a look at the videos and let me know what the issue is. Before this it ran great then we took it out for fun. 17' bass boat.....running full throttle in 2' waves. Ran fine for 20 minutes then started to skip/spit. Hard idle/stalling to get back to the dock. Sounded like a vacuum leak at the dock but then when we got it home and the cowl off. Im thinking either the timing or water in fuel. I would love a quick reply as we need to take it out Friday!

http://www.youtube.com/watch?v=K4AHjMO6jvc

http://www.youtube.com/watch?v=eslMghlqxQk

 

[roscoe]

Re: 85hp Force - Backfire? - w/ video

Try fresh fuel in a portable tank.

 

[jerryjerry05]

Re: 85hp Force - Backfire? - w/ video

In the drive way you need to have the motor straight up and down.Won't run right.Low trailer? Run it up on small ramps.Check the fuel for water.
Install a water/fuel seperating filter.Available on this site or any marine place even Wally World.
Replace the diaphram in the pump.Replace all hoses and squeezie.Do a compression test too(just in case)
Timing won't usually change unless you do something to the linkage.

 

[devl]

Re: 85hp Force - Backfire? - w/ video

I just wanted to update in case anyone else runs into this very weird issue. The problem is a transfer port cover gasket is blown causing the #1 cylinder compression/fire to blow out the gap. I didnt even know this part existed but after an engine inspection while idling close to dark outside I saw the flame. This was actually a very real fire hazard so just a tip: keep a fire extinguisher handy while doing any engine work!

 

[Frank Acampora]

Re: 85hp Force - Backfire? - w/ video

Those gaskets--especially if they are original-- do not usually fail. You need to invesigate WHY it failed.

Since you will have the cover off to replace the gasket anyway, inspect the piston through the bypass ports. Remove the sparkplug and get some light through there.

Rather than wait for a new gasket, buy some 1/32 thick gasket paper from the auto store and make your own. Use a childs hole punch to make the bolt holes. It will take you about 10 minutes to make a new one.

 

[devl]

Re: 85hp Force - Backfire? - w/ video

Thanks Frank, unfortunately I already ordered the gasket. Ill do a thorough inspection when I change it and then a compression test.

 

[yoyopurple]

Re: 85hp Force - Backfire? - w/ video

hey i have a 85 force and it does the same exact thing after 3 coils and a impeller change with a carb tune.

how would i go about changing this port transfer gasket?

 

[devl]

Re: 85hp Force - Backfire? - w/ video

@Frank - the issue was just a loose bolt. Right where the gasket blew out the bolt was barely in there.

@yoyo - This is kind of a rare problem but I guess it wouldnt hurt to check. If you remove the plate your coils are attached to right behind there are the transfer ports covers. Mine was easy to see it had a blown gasket as it was sticking part way out from under the cover.

 

[yoyopurple]

Re: 85hp Force - Backfire? - w/ video

hmm... i have the same exact year force, and it misses"sneezes" exactly like that.

But when i went to go in for the transfer port gasket they said there was 3 gasket, that i would have to possibly change.

and when i opperate at 4500rpm at 3/4 and i push it that last 1/4 at WOT the rpm doesnt change, and sounds as if im running to lean and not enough gas is comming in.
I had the carbs synced adjusted and rebuilt. replace the fuel diaphragm just incase and th e screen and pump itself was in excellent shape. all fuel lines and primer bulb are great.
A buddy told me if there was a leak that acted like a vacuum will make my motor run like this

thanks for replies saves me a bunch of headaches