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Port & Starboard Engine is off by 200 RPM's is this normal?

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Port & Starboard Engine is off by 200 RPM's is this normal?

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Old 04-29-2017, 09:15 PM
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Default Port & Starboard Engine is off by 200 RPM's is this normal?

I have a 2008 Fountain Lightning with staggered twin 496HO. My Port & Starboard engine is consistently off by 200rpm's. Is this normal? Water pressure , temps etc...are all the same.
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Old 04-29-2017, 09:42 PM
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It's a built in design. You need more skanks on the higher revving side!
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Old 04-29-2017, 09:48 PM
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Take your props to a prop shop and give him the info and he will tune the props so that the RPM's match assuming that both engines are running good and not missing.
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Old 04-29-2017, 09:50 PM
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Have you checked the trim levels out of the water? I was about 200 off also and did a quick check end realized I need to tweek my trim switches alittle cause the drives were at different points when gauge said they matched, ever since I'm dead nuts on with each other, I didn't have mechanical indicators like you more than likely have
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Old 04-29-2017, 09:57 PM
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My one motor runs slightly lower RPM's due to the power steering pump causing a little bit of lag. Does you lower RPM motor have the pump on it?
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Old 04-29-2017, 11:11 PM
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Your props are fine. It is impossible to accurately trim with the trim indicators due to cable stretch, different lengths of cable for port/starboard engines, rigging, etc.

The past two years of having this boat I have found it impossible to trim out properly. This has affected my top speed and with constantly trying to find the sweet spot balancing the drives with each individual trim switch I'm looking more inside the boat then outside watching where I'm going.

I just installed a Drive Sync from MDC (Marine Design Corporation) and it syncs up the slow drive to the fast one to within about 1/64th of an inch I believe. Basically when setting up, drives are in the full down position and you index the trim senders, then calibrate to full up and you are done. Now I will be able to use the throttle mounted trim switch instead of the dual panel switches.

It's awesome to watch the drives stay synchronized while on the trailer. I will have the boat out in the next few weeks and hope to finally break into triple digit speeds.
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Old 04-30-2017, 12:40 AM
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Found a plug wire bad on one of my 525's using the Rinda scan tool in the cylinder test mode ......was about a 200 rpm diff.
It payed for itself right there
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Old 04-30-2017, 07:55 PM
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Thanks for all the tips. I'm going to start the process of elimination and try to narrow down the issue.
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Old 05-02-2017, 10:04 AM
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Maybe an issue with throttle cable adjustment as well.
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