28 SPL engine misfire

First time poster, looking for some help, thanks in advance. A little background on the engine, it's an 87 Johnson 28 SPL long shaft, I've cleaned the carb, conducted a de-carb on it using sea foam deep creep and sea foam in the gas tank, I have the proper spark plugs (champions), just haven't changed them yet as I'm still working on the de-carb. Well, while trouble shooting the misfire, I switched the plug wires and found a wire somewhat erratic on resistance meter reading. Also, the bottom plug fell off while running the engine at above idle and the engine actually ran smoother than when both plug wires are on. The only thing I have not accomplished yet is the link and sync, it appears the timing is off for the bottom cylinder (#2 cyl I would guess) although, not sure how that would work. Thank you again for any input regarding this.

Re: 28 SPL engine misfire

How about a compression test ??

Re: 28 SPL engine misfire

By the way, welcome to iboats

Re: 28 SPL engine misfire

Thanks Ken, checked the compression, both cylinders 110 psi. Any ideas?

Re: 28 SPL engine misfire

try switching the coils, completely swap them, see if it follows the coil.

Re: 28 SPL engine misfire

Switched the coils, it appears to be running better, still rough though and it smokes a lot, but it always did that. One thing I found was a few wires that were exposed with the potential to ground out against the block, not sure what all of them were, but one of them contained the inline fuse (covered them up with electrical tape for the time being). When pulling the plug wires off this time, it ran worse, no matter which one. Need to get it on the lake to really open it up and see what happens.

Re: 28 SPL engine misfire

i take it that it is electric start. the line with the fuse is the positive feed to the ignition switch.

Re: 28 SPL engine misfire

Yep, electric start. Well, seeing as how I haven't blown the fuse yet and it starts, then that's obviously not one of the issues. Thanks for the info though, good to know for the future until I can find the good manual for it.

Re: 28 SPL engine misfire

Took the boat out to the lake today and it seems there's a new/hiding issue, it seems the backfire/misfire has disappeared. When operating at full throttle, it seems to want to stall out, if I push in the electric choke, it seems to recover, but not always. The primer bulb is always soft after this attempt at stalling. One suggestion made to me was the possibility of the fuel hose being too long, can that be the case here, or is it possibly something else. Thanks for any info in advance.

Re: 28 SPL engine misfire

you now have a fuel restriction issue, clogged filter, weak fuel pump, alr leak fuel line, vent not open on fuel tank.

hose length should not be an issue.

Re: 28 SPL engine misfire

I've checked all the hoses, put hose clamps on all fittings/hoses and it continues to sputter, fuel is good. Does this engine have a fuel filter, looking at the parts breakdown, it doesn't appear to show one, unless it's in the gas tank which is brand new. Also, it looks as though the fuel that is in the bottom of the housing is coming from the carb. Any more thoughts.