Ignition Coil Issues?
 

I have a 99 VP 5.0GL with SBC and yesterday had odd ignition issues. I think the coil but wanted some other advice.

Boat ran great for ~30 minutes then would notice it would feel like it would drop cylinder or two in low speed , no wake areas, would run OK on plane (might have been slightly down on power, was hard to tell, if it was not by much). As boat ran longer it ran worst. I noticed when I ran the trim pump to trim up or down would change the way it ran, usually would run smooth. (weird huh). I had a small tool kit along and ran a 12+ wire directly to battery to by pass boat wiring, switch etc. thinking it might be voltage problem to battery (bad connection, high resistance deal). Ran exactly the same with boat wiring by-passed. Odd, not boat wiring then. We stopped for lunch threw anchor and ate lunch, when boat cooled ran OK for ~ 30 minutes again then same progression is poor running. Stopped again to chill and swim in cove, boat cooled off and ran fine for a while to get us back to ramp, was starting same deal when we got to ramp. Got home (boat had cooled on trip home) and fired right up to flush it, all 8 cylinders sounding fine. I would think coil all day long, but why the heck would the trim pump have effect???

The boat has what appears to be standard cylindrical ignition coil, (Prestolite distributor) I wonder if it it is marine specific in case nobody has VP part locally.

Sorry for the very long post.

i'm not sure its the ignition... the coil is a really simple device... its an oil filled capacitor. yes they fail but rarely and while i read a lot about them getting hot and not working, in my experience that is an extreme rarity... and , as will be written in a few minutes by 50 people, they are cheap so buy a new one and satisfy yourself that that's not it. for me, tho, if it was to be ignition, i would look at the amplifier ( if it has one) the electronics are far more susceptable to thermal issues.

having said all that though, to me it smacks of the fuel overheating either in the float bowl because the the carb is heat soaking or something along those lines. an easy test pop the hatch when its happening and just feel the carb. if its 200 degrees, that will tell you something and if thats the case you should be able to test the fix by cracking the hatch a bit when you are running to let the sytem stabilize and see if the problem goes away. its hard to think of why this sort of thing happens all of a sudeen when everything used to work fine the way it was but sometimes if the float level drops it's easy to have happen. when the fuel gets really hot, the system leans out and gives you your sort of issue...

is it electronic ingition or points? I have seen coils do a partial breakdown after they got hot, or the elctronic pick up in the dist., most of the time they shutdown completely, but not always, and like mentioned, check for heat soak.

It is electronic ignition (no points).

When it runs rough it seems rich (unburned fuel) so I really think it is ignition related. The coil is easier/cheaper so I am going to start there, but also realize the module in distributor might be bad. Have old coil off and going to take it to local autoparts store and try to match it up .

During winter did you unhook the batteries? Make sure all the grounds are tight. Was this you first trip out this year year, If so was the fuel treated and do you have new fuel in there now or is it old gas from last year? Have you pulled fuel filter off to check for water? If all that is ok then you might want to pull the spark plugs and look to see if any are cracked, Before you pull the plugs out you should try to wiggel the plugs to see if you can tell if they are loose or cracked, if they are cracked then some times you can hear them crack a little more easaly or it will feel loose. If they are ok then i would try runing the engine at night time in the total dark and look at all the spark plug wires at each end to see if you can find a spark going to ground some where, Also check your dist cap for any thing even if it is all new some one may have done a bad job. Hope this helps, Good luck

I put a 360 crate engine 380 HP in a 92 Dakota. I ran into a similar situation, truck would run fine for 15-30 minutes and then it just crapped out. Yup it was the coil. May not be the same problem but a good place to start. As one of the other posters indicated coil is a quick semi cheap first shot.

I bought a new MSN master blaster coil this afternoon and will install tomorrow night after work. Not the 1st run of the boat, I am lucky enough to boat year round and boat gets about 200hrs a year, ran fine 2 weeks ago when used last. Might be bad fuel or tune up, bit sure seems ignition related since comes and goes with temp. Cap/rotor etc. has about 100 hrs on it so pretty new.

Cleaned all connections, replaced coil with MSD Blaster and sea trialed boat tonight. Ran fine on muffs for ~20 minutes and in water for another 30 minutes. Then shut off like you turned the key off. I have +12V to coil "+" and no voltage pulse when engine turning over on "-" side. I think the module take the place of old school points and condenser, so should pulse as the hall effect swings place the toothed gear right? I believe I have found the issue, bad module in distributor. Experts agree before I drop $175 on it?

ttt

It makes some sence it could be the module, I would hate to see you waste your money if it is not it, That is a hard one to find some times becouse you normaly would be needing to be watching every thing that could be makeing it run that way at the time it want's to do it, Like watching the fuel and spark/timing and takeing temp readings all over the engine in order to see what is really going on with the engine. Have you tryed to restart it now after cooling? If it did not start you might want to rehook up the old coil just to see.

Trouble shot it some more last night and 99% sure it is the module. Factory manual had a pretty good section and you set Hall Effect between two teeth and check voltage on both side of coil. With module hooked up low voltage on neg side, unhook module and goes to +12V. Manuals says that means module is shorted inside (makes sense).

So I removed it from dist. and the potting material on bottom side is cracked, I bet moister got into it. New one is on the way, should be here Tuesday or Wednesday.

Bought the new module and arrived today via UPS and I installed it tonight after work. Boat fired right up and runs fine on hose, going to sea trial tomorrow after work. I did check the ohm readings of my new high output MSD Master Blaster coil. The primary side is inline with factory coil (1.5-->2.0 ohm) but the secondary side is about 5k and factory specs are 9-10k. Hopefully the new coil is compatible with my ignition.

Update: Sea trailed it last night. Ran it around for about an hour and half, ran good whole time. Power was back, no low speed misses etc. :-)

Bring on the weekend.

you have to be carefull as some coils and ignitions don't mix...Rob

most blaster coils are oil filled and should be mounted in the vertical position. the msd high vibration coil is epoxy filled and can be mounted in any orientation

I have the coil mounted vertically so good to go there. I wonder how I can determine if my coil is compatible. I would think the primary side resistance is most important to the rest since it is weird to the module but???????????

Called MSD, either I got a guy that was having a case of the Fridays or their customer service suks. He wouldn't tell me anything. Answered like he was totally reading from script. Eventully I asked him if I was understanding ignition theory is that as long as the primary side resistance is same I cant hurt module and he said "yes...in theory, but he is still not sure my new coil is OK". WTF.

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