1994 Force 90 Dead Cylinder?

['94 Pro-Line 170]

Last weekend it was running perfect at about 5000 rpms when it started running rough. It wouldn't take the throttle over about 2200 (spit and sputter, no power). Back off and it seems to run better. Came in at 6mph. Never recovered. Held pressure on primer bulb (no change). Inline fuel filter is clear. Seems to be in the top cylinder (removed plug wires one at the time-runs ok without #1, barely runs without 2 or 3. Swapped 1 & 2 plugs, but problem still in top cylinder. I'm looking into the carb, but it is sooooo clean! The others were too when I looked at them a couple of months ago. Planning to re-build fuel pump (can't hurt). I stuck my finger in the intake hole after removing the carb. One reed seems a little sticky, but not hard to push open at all. #1 seems to have good spark (accidentally shocked myself silly). Compression is good in all 3. Don't see any water. What am I missing?

 

[roscoe]

Re: 1994 Force 90 Dead Cylinder?

If spark is good, and compression is good, then it is fuel (carb).

It may look clean, but it doesn't take much to clog a jet.

 

['94 Pro-Line 170]

Re: 1994 Force 90 Dead Cylinder?

Thanks, it really does seem like trash in the carb. The "main jet" has a pretty large hole in it and is clear. I can cover it with my finger and blow up through the main nozzle and feel the air coming out in the throat. I guess I'll go ahead and take the whole thing apart. I didn't want to because the idle tube sticks down through the main nozzle making it hard to use a screwdriver to get the nozzle out. Maybe I'm not getting the fire I think I am. I'll check that more closely. Didn't crank on it with the plug out where I can see the spark. I thought it was running ok under 2200, but it must be missing at idle too because that's how I tested to find that #1 was not contributing. I may try spraying fuel mix directly in the throat and see if it will run. Any advice is welcome. I have a Seloc manual that I've been reading. I haven't had the boat long, and I don't know all the history on it. It idled really rough and flooded when I got it. I adjusted the idle mixture screws as the manual said, and it made a big difference. The only other thing I did was replace the rectifier (not charging and old one was visibly burned up). I got a deal on it because it was jumping out of gear. I had the rounded edges machined flat fwd gear and shift dog, re-shimmed, new seals. No more shift problems. Now I'm ready to just go fishing without fighting these little odds & ends.

 

['94 Pro-Line 170]

Re: 1994 Force 90 Dead Cylinder?

Ok, I know this is going to sound out-of-the-ordinary, but I think I have found the problem. I checked for spark on the top cylinder, and it was good. The engine had been making a rattling sound at high rpm, but I had assumed it was a broken-off bolt or something as there were several that hold the cowlings and covers on. Turns out it was a flywheel magnet that had come loose and was sliding down. Every time it went around it hit the stainless steel shield under the stator. I pushed the magnet back up, and it started running smooth again. Apparently, this was throwing the timing off. I also notice that some of the plastic from the stator has been shaved off. Hope it wasn't touching. I'm planning to remove the flywheel and secure the magnet with JB Weld. I haven't been able to get the bolt loose yet. It's been soaking several days. I'll put the torch to it this evening, and if that don't get it I'll haul it to my dad's and use the impact wrench.