Automatic Throttle down feature on a Grady White Marlin?

[sickday]

Boat: 2001 Grady White Marlin 300
Power: Twin O/B OX66 Salt Water 250 Two Strokes

Symptom: In rough seas, while under power (2k RPM or more) starboard motor is throttling back on its own. Its always done this but I've never noticed it with just one engine and not as frequent. And it seems to be doing it in conditions less than what I would consider bad. Always occurs on the backside of the swell. For the most part, the engine runs well and purrrs while on plane at cruising speeds and on calm water :hmm

Question: Has this ever happened to anyone? Is there a simple fix or adjustment. Should I be worried?

 

[BobP]

No it doesn't, unless you are letting go of the binnacle lever. There's a friction adjustment for that.

 

[seasick]

Is this surging ( Revs go down and back up) or are the revs actually lowering and staying there?
In the first case, I have seen this happen when the VST screen gets partially clogged. I don't understand why exactly that occurs on rougher seas but it definitely does.

The second case could be the throttle friction but in that case, you would notice that the throttle moved and that moving it back restores the revs.
You may have a loose connection somewhere or a loose throttle linkage ( somewhat common). I guess more investigation is in order.
Let us know what you find

 

[sickday]

Yes, the engine automatically returns/Revs back to the previous RPM. I thought I heard a clicking (at the time of the issue) in my Throttle Unit at the helm, but I just figured I was hearing things. :hmm

Thanks for the responses,,,,I'll look into both issues

 

[Bill_N]

Just a guess but it could be some water in your gas that gets ingested only when it's rough. Switch your tank feeds and see if it has any effect. If not then you ruled that out...

 

[Fishtales]

I'd say it is the throttle friction adjustment. Try that first.

 

[seasick]

I'd say it is the throttle friction adjustment. Try that first.

If it were and the throttle moved, the revs would not come back up. It is something else.

 

[sickday]

From what I've read and learned, the evidence is pointing toward the VST screen/filter.

My issue is now, is this a project that I can handle on the water? Seems like a pretty involved project.

 

[sickday]

It was clogged VST screens. Solid layer of residue that made it barely transparent when holding up to bright light. Boat now runs better, stronger, faster then I've ever seen it since I bought it used 3 years ago. Oh, and its BURNING LESS fuel. Did approximately 100 miles yesterday and burned less than 70 gallons. If you have 2 stroke yamahas and have never serviced the VST screens, I would highly recommend it at your next service.

Thanks for everyone's input!

Matt