1989 omc 5.7 misfire above 2500rpm

[Paul.v]

Hey guys, I have a 1989 OMC 5.7 in a 19' cuddy. Under 300 hrs on 2006 engine. This year I changed the points, and condenser they were surprisingly corroded as well as the rotor & cap replaced. Points set to .017. Starts fine but misfiring on acceleration. I pulled the fuel filter/water seperator , clean, no water. Installed new filter no change.
coil is 1.7 ohms primary, 11k secondary.
Compression is 150-160 on all cylinders on cold engine .
timing checked, mechanical advance is free & springs look good.
I can get on plane but anything above misfires badly. Not sure if its electrical or fuel issue..
Any thoughts?

 

[alldodge]

Check you fuel pressure between pump and carb, it should be between 3 to 7 psi

 

[Scott Danforth]

Check the dwell along with fuel pressure

 

[Paul.v]

Thanks guys, my line from fuel to carb is solid, I guess I’d have to cut it to put in a T ? I’ll have to purchase a gauge. Might be easier to just put in a new pump considering this one could be original??
ill check dwell too but didn’t think it would be far if gap is set on new points...?
thanks for your input!

 

[alldodge]

A vacuum fuel pump tester cost about $20 an can probably be rented from an auto store. You can make a Tee out of rubber fuel line and clamps. The fuel line will go over the end of the metal one. Only thing you will need is the fitting for carb and it can find at an auto store also,

 

[HT32BSX115]

Don't cut the line. Just make up another one using flexible fuel hose and appropriate fittings. All you're doing is a temporary test. If your fuel pump is REALLY old, you might consider replacing (or at least having a spare on hand) but test first!

I can get on plane but anything above misfires badly.

How "badly"? If it's REALLY bad it might be your ESA activating.....Make sure your Shift Actuator is centered once you're in gear and advancing the throttle.

 

[Paul.v]

Ok, fuel pressure is consistent 7psi, dwell was at 22deg, adjusted points to reach 28deg, still same... could it be carb?

 

[HT32BSX115]

Ok, fuel pressure is consistent 7psi, dwell was at 22deg, adjusted points to reach 28deg, still same... could it be carb?

It could absolutely be the carb. If it's old, you might consider rebuilding.

If your wiring & dist cap are old, replace them too.

 

[Paul.v]

Thanks, distributor cap is new.

 

[Paul.v]

just tinkering some more..I notice some side play on the distributor shaft, maybe 0.010 . I could see it in the points.. any thoughts?

 

[alldodge]

The play (if side to side) will cause all kinds of problems with ignition. The .010 wobble can change the point gap +/- .010

Need to rebuild or replace the distributor

 

[Paul.v]

Thanks AllDodge, I didnt think it looked right. its not sloppy but I can definitely move it by hand so it could be interesting at 3000 rpm. May not be my issue but needs to be addressed. Any recommendations on replacement?

 

[Scott Danforth]

just tinkering some more..I notice some side play on the distributor shaft, maybe 0.010 . I could see it in the points.. any thoughts?

go to napa and spend $5 on a distributor bushing.

 

[Paul.v]

Thanks Scott, I'll look into that for sure!. I checked dwell today. from idle to 2000 rpm I lose 5deg of dwell

 

[alldodge]

With only 5 degrees I don't see an issue

 

[Paul.v]

I read that 3deg indicated excessive wear..???

 

[alldodge]

I read that 3deg indicated excessive wear..???

Your correct, when I read your comment yesterday I thought it was idle to WOT but it was only to 2K

 

[Paul.v]

So, thinking out loud, at idle, dwell is ok, as rpm increases dwell is decreasing having less time to build energy in coil so weak spark? I'm looking for bushing/bearing. Napa Canada doesn't have it as far as I can see., I may go to local bearing shop. May be a week or so but I will update progress. Thanks guys for the input!

 

[MBAKER]

I would change the condenser again. Put in a all new distributor on a previous boat years ago, started acting the same way. Checked all the same stuff you are, then on a whim swapped in the old condenser and ran like a top. Never a problem after that. Just a thought but its an easy and cheap fix to try.

 

[Paul.v]

I would change the condenser again. Put in a all new distributor on a previous boat years ago, started acting the same way. Checked all the same stuff you are, then on a whim swapped in the old condenser and ran like a top. Never a problem after that. Just a thought but its an easy and cheap fix to try.

Good idea! I will try that also. Thanks!