Indmar 325 spark plug GAP

[BOWZ]

Hey guys, I have found a ton of information reading old threads on here and asking questions, but have not come up with any one else noticing conflicting information regarding gaping spark plugs between Supra's 2003 online owners manual and Indmars online operators manuals.

During winterization I pulled the spark plugs to spray in fogging oil and the gap looked huge, I checked all of them and were just a touch over .060. The boat ran just fine for me, I never pushed it hard in the upper rpms for more than 10 seconds but it never got above 4200 rpm, full fuel, 400lbs of lead, front bag 3/4-full, 2 adults and 2 75lb dogs so I'm wasn't to worried about not meeting max rpm range. I have always averaged 6-10GPH for the 60+ hrs I've had it.

Via Supras web site I was able to download my 2003 owners manual due to not getting one with the boat. On page 57 it has the spark plugs as AC 41-932/MR43LTS with a GAP of .045
Via Indmars web site I was able to download 2003 to 2005 online operators manual. On page B-1 it doesn't have a TBI engine but a MPI with a AC 41-932 spark plug with a GAP of .060.
With that nugget of information made me wonder if I have a 2002 model year engine in my boat, so I downloaded a 1994 to 2002 operators manual. On page B-1 it has a TBI with a MR43LTS plug and a gap of .045 but makes no mention of the AC 41-932.

The plugs currently are AC 41-932 and look to be burning a tad rich and gapped over .060 but besides that just fine. So what do you guys all think? After my first tank of fuel next spring I will change out plugs, wires, cap and rotor. I want to figure out what plug I should be running and then find the best place to get everything online/dealer. Thanks in advance for any help!

Bowz

[BOWZ]

wow, over 50 views and no input! anybody anything?


Bowz

[Jetlink]

Personally, I would run the gap that the engine manufacturer recommends.

[docdrs]

I would be more concerned with the max rpms. If you are only getting 4200 you are over propped for your purposes and putting more strain on the engine. These engines are brutes but it may make a difference over the long haul. I'd run at .045 as per boat manual and assess. .060 for mpi is most likely due to a better atomization and fuel to air mixture than tbi. Having a gap too wide could result in possible misfire. jmo

[BOWZ]

Personally, I would run the gap that the engine manufacturer recommends.
I think that makes more sense to.


I would be more concerned with the max rpms. If you are only getting 4200 you are over propped for your purposes and putting more strain on the engine. These engines are brutes but it may make a difference over the long haul. I'd run at .045 as per boat manual and assess. .060 for mpi is most likely due to a better atomization and fuel to air mixture than tbi. Having a gap too wide could result in possible misfire. jmo

As far as over propped I am for sure when I have it weighted down for surfing and was probably a little over when I opened it up as stated above. I think if I were to run the boat a longer distance full throttle I could have gotten a few more RPM to be closer to the 4400-4800 recommended RPM but would have still fallen short. I just cannot stand the typical hot oil PSI on these 350 blocks, hence only 10 sec full throttle burst. I am now running Amsoil with the hope that I don't have such a drop in oil PSI when it is hot.

I'm on the same page as you with the A/F mixture. It would be nice for supra to not have conflicting information with the engine manufacture. Maybe worth me sending an email, but I can hardly believe I'm the first one to catch it.

To go back and touch base on the prop, my plan is to upgrade my ballast and finalize my surf gates this winter. After a few trips next summer I will have an idea if I'm dialed in for surf and if so will be able to get the correct prop and use the current for a spare. I currently run close to the same rpm for surfing at 10.5 as I do wakeboarding at 21.. Yeiks.

Thanks again for the response!

Bowz

[CJD]

Run .060". It sounds like the Supra manual was not updated timely for the electronic ignition.

[BOWZ]

Run .060". It sounds like the Supra manual was not updated timely for the electronic ignition.

The Supra manual wasn't updated and the (2003-2005) Indmar manual doesn't have a TBI section. I'm pretty sure that I have a 2002 model year engine in my 2003 supra. Indmars 2004-2002 manual has does have TBI section with a gap of .045". So I think it should be .045" gap. I think I might have just confused myself. haha


Bowz

[Engine Nut]

Here is the straight spark plug scoop! If your 5.7L engine does not have catalytic converter exhaust, use the MR43LTS spark plugs gapped at .045" even though the engine may have come from the factory with 41-932 plugs.

If you have an engine with catalytic converters us the 41-932 or 41-101 plugs gapped at .060".

[BOWZ]

THANKS LARRY!


Bowz