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Lose spark above 4000rpm

Nitrofan16

New member
I have a 1988 Cris craft with a 4.3L & an omc drive. Boat runs great from idle to 3000 rpm then starts popping and studering . When you put a timing light on it you can watch the spark go away. Seems like the slower you rev it, the longer it takes to lose spark but never rev's above 4000. I used to run all day at 4600 rpms. What am I missing ?
 
I'd suggest going back over your 'new' work.....If it was ok before the 'mod' then the issue is highly likely coupled to the 'mod'....
 
The issue was the reason for the mods. Unfortunately I have double and triple checked everything. Water tested 4 times same result, seems to get worse the longer you run it, "better" when engine is cooler. Did compression test & all 6 were within 3# of each other.
 
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We have changed both feul filters both were clean and free of water. Someone mentioned shift assist? Not sure what that would have to do with it?
 
I have a 1988 Cris craft with a 4.3L & an omc drive. Boat runs great from idle to 3000 rpm then starts popping and studering . When you put a timing light on it you can watch the spark go away. Seems like the slower you rev it, the longer it takes to lose spark but never rev's above 4000. I used to run all day at 4600 rpms. What am I missing ?
Sounds like your spark isn't hot enough.built in condenser ?
 
All brand new, just switched to electronic ignition

If problem same as before, then likely something you didn't change... Are you using the same coil?

re: " Used to run all day at 4600 rpms(sic) ".... All day at 4600 rpm is " Put a $100.00 bill every hour in the "buy a new engine jar" boating". You should limit continuous operation to 80% of MAX WOT, i.e., 3680 RPM for reasonable life.
 
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Ended up figuring out that I started with a bad condenser and ended up with a bad rotor (brand new) 3 days of trouble shooting to find the rotor problem, crazy. It's fixed now and runs great. When I said 4600rpms all day I meant in short bursts. In the end I appreciate everyone's input and time THANK YOU ALL I'm now hooked on this forum !
 
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