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Optimax 225 DFI - RPM's bouncing

Old 07-10-2020, 08:29 AM
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Default Optimax 225 DFI - RPM's bouncing

I have a 2002 Optimax (225hp) DFI. Last year i noticed an intermittent problem - when i am at cruising speed at approx 4200 rpm's, my rpms
would just suddenly drop to about 3800 rpm for a split second and than go right back to 4200 rpm's.
This condition would continue to repeat itself every 10-15 seconds.

This seems to come and go as it is very intermittent making it difficult to troubleshoot. some days i can go ocean fishing for 10 hours and it doesn't ever happen.
Other days it happens right away.
Its not a false gauge reading as i can certainly feel the boat slow down for a split second.
It can happen on completely calm days with flat sea conditions.
anybody come across this condition or symptom ?
Thanks Dan
Old 07-10-2020, 08:32 AM
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Sounds like it may be a Coil dropping out.
Old 07-10-2020, 08:36 AM
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OK thank you !! - i really hate to buy 6 coils without any diagnoses., any suggestions troubleshooting a coil. that is intermittent ?
Old 07-10-2020, 08:40 AM
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At idle disconnect coils 1 at a time, your looking for no change in idle. Could also have clogged injector or bad plug wires. Isolate the cylinder and go from there
Old 07-10-2020, 09:05 AM
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Ok - thank you. i will try your suggestion this weekend. , my only concern is that the issue is intermittent so i am not confident i will be able to identify a faulty part during testing at the dock.
Dan
Old 07-10-2020, 09:08 AM
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Could pull plugs to see if 1 is fouled
Old 07-10-2020, 09:15 AM
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I'd check wiring also I have had issues with bad connections at coils and injectors due to corrosion. First maybe wiggle them at idle and see if you get any change in sound? Unplugging them and plugging them back in a few times could help clean the contacts then add dielectric grease on the last insertion.
Old 07-10-2020, 09:18 AM
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I pulled plugs last year - all 6 looked the same.. and i pulled again last month- all 6 still the same .
FYI - i installed brand new plugs in May 2020.
Because this issue is intermittent i assume t is why i cant see any signs of fouling on the plugs.
Old 07-10-2020, 09:23 AM
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Thank you - i am a Dielectric grease junky !! LOL. - absolutely love the product.
i use it every spring season on all my wire connections: coil packs , fuel injectors, spark plug wires and my Air injectors
no corrosion on my wires..

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