Spark plug question for Indmar Assault in 2014 Moomba Mondo

[bjrow]

OK so 10 yrs on I'm finally doing the spark plugs and coil/module.
have replaced the rotor, cap and leads, original leads probably ok and have kept as spares.
The spark plugs are ACDelco 41-101 but cannot seem to get them here in Oz, purchased the 41-993 as the 2014 Moomba manual has both types listed.
The engine is MPI and has Cats, the gap in the manual says 0.040" however I noticed in the 2015 Manual it has the same sets of plugs but a gap of 0.060".
So a bit confused atm and wondered if anyone had been down this path as well.
The 41-101 I can only get thru Amazon Oz and frankly they'll be knockoffs for sure, they are like half the price but not falling for that one.
So just wondered about the gap 0.040" or 0.060", I can pull out one of the old ones but I'm wondering if there'd be much to go by after 10+ yrs albeit 190hrs on the clock.

Best Regards, BruceR, Melb AUS.

[MJHSupra]

OK so 10 yrs on I'm finally doing the spark plugs and coil/module.
have replaced the rotor, cap and leads, original leads probably ok and have kept as spares.
The spark plugs are ACDelco 41-101 but cannot seem to get them here in Oz, purchased the 41-993 as the 2014 Moomba manual has both types listed.
The engine is MPI and has Cats, the gap in the manual says 0.040" however I noticed in the 2015 Manual it has the same sets of plugs but a gap of 0.060".
So a bit confused atm and wondered if anyone had been down this path as well.
The 41-101 I can only get thru Amazon Oz and frankly they'll be knockoffs for sure, they are like half the price but not falling for that one.
So just wondered about the gap 0.040" or 0.060", I can pull out one of the old ones but I'm wondering if there'd be much to go by after 10+ yrs albeit 190hrs on the clock.

Best Regards, BruceR, Melb AUS.

Here is a past post from Larry at Indmar - aka "Engine Nut"

https://forum.moomba.com/showthread....Spark-Plug-Gap

[Holdmybeer]

I know the plugs are 10 years old, but at 190hrs they are more than likely still fine. You could probably measure an accurate gap also before ordering new ones.

The coil, rotor/ cap, and wires can all decay so time plays a factor. I have never seen the ceramic or copper of a spark plug decay.

[HFarr]

So you have had that boat 10 years and only put 190 hours on it?

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[MJHSupra]

Those GM motors were easy to work on and tune up.


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[bjrow]

Thanks for your reply's.
Yeah first time out this season and under lots of load it started to miss fire, load reduced ran fine.
Replaced rotor, cap and leads, went out and miss fired about 45mins into our ride, not loaded. Was pretty bad, at higher rpms it seemed better but aborted the day as a precaution.
So have new plugs and a coil with module, fingers crossed otherwise it's off to service guys and throwing cash away most likely.
Will take one of the old plugs out and see what gap they may have been then set the same for the new ones.
We get out a fair bit 6-12 times a season each trip we're out for 4-5hrs only and the engine shut off if we are not going somewhere.
I look at the few new boats on the lake and turn green with envy but at 250K plus nowdays I'll pass and enjoy what I have.
Thanks again, will advise once I find the fix, hopefully.
Cheers BruceR, Melb AUS.

[Tommy2slow]

Is your fuel fresh? Those misfires could be a symptom of stale fuel. Try adding a bunch of fresh fuel to the tank and go for a blast before turning to expensive repairs.

[bjrow]

Thanks for your suggestion, have trialled that without success.
Smells like unburnt fuel coming out the exhausts when running badly, figured I'd try the ignition stuff then if no good must be fuel related, it's off to the doctors if that's the case.
Cheers BruceR, Melb AUS.

[Holdmybeer]

Thanks for your suggestion, have trialled that without success.
Smells like unburnt fuel coming out the exhausts when running badly, figured I'd try the ignition stuff then if no good must be fuel related, it's off to the doctors if that's the case.
Cheers BruceR, Melb AUS.

Bruce,

If you are smelling unburnt fuel, you are on the right track.
Ignition components most likely. I would guess coil if you did the plugs already. Try running platinum plugs this time. They are a little hotter and are gapped at 0.60 for catalyst motors.
Only other thing it could be after that is leaky fuel injectors from gummed up old gas or carbon deposits.

Cheers

[bjrow]

Right, just in from doing the plugs and coil module.
We've owned the boat from new, the plugs in it originally were marked as 41-101 and were gapped at 0.060", all 8 of them. The Moomba owners manual says 0.040" as well as the Indmar engine manual for 2012 thru 2014. I ended up gapping the 41-993's at 0.060" and put them all in. Started the boat and it ran somewhat same as before for the 20 or so seconds I let it. Replaced the coil and module assembly and ran it again, quite a noteable change in the way it ran. Initially was hunting (cold start) and as it warmed over 15 secs or so the hunting smoothed out to a steady cold start rpm speed, phew!. Let everything cool down over a few hours (cat exhausts were only warm to the touch after running) then ran again, nice smooth cold start idle straight up. Seemed very eager to run compared with what I had become used to. Will test on the hose for hot idle then take to the lake in the next week or so. I did notice on the original coil a dot of paint that was red in colour, the new one (bought from Indmar parts here in AUS) had a blue dot of paint, not sure what that is supposed to reference if anything at all. Maybe someone knows and can chip in.....
So far pretty happy, just have to wait for the rain to clear and give myself a day off during the week.

Appreciate all your comments and suggestions.

Regards BruceR, Melb AUS.