www.iFourWinns.com

Any thoughts as to what could cause a 10mph top end loss? Engine is not mis-firing or stumbling, starts right up, idles smooth, full throttle RPMs are between 4200-4300 rpms. Slow to plane, it used to get up and out of the hole quickly...and RPMs only slowly pick up. Feels like the boat’s dragging or really weighted down. No water in the engine compartment. Top end is usually somewhere around 48 mph but we can’t get over 36 mph. Oil pressure’s fine, new oil, running perfectly besides the power loss. Steering feels stiffer than usually and possibly there’s a loss of responsiveness/directional control while reversing.

Thoughts on possible issues to troubleshoot please... TIA

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2008 278 Vista | 8.1 Gi Volve Penta
Mark II C Touring Zodiac w/9hp outboard

Check and see if something is wrapped up on the prop. Piece of rope or plastic.

We can’t see or feel anything visually - being a duo prop, could it be stuck somewhere we can’t see without removing the prop? My son did get a rope caught in the prop the last time out?

Do duo props suffer from “spun prop”? I believe I saw somewhere that they are solid... ?

While testing yesterday the throttle did not give the engine additional power from the half way engaged point to full throttle.

Fuel pump possibly bad?

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2008 278 Vista | 8.1 Gi Volve Penta
Mark II C Touring Zodiac w/9hp outboard

Husband wanted me to add that there was no discernible increase in power or RPMs from the half throttle to full throttle.

Fuel pump possibly bad? Although engine starts right up, is completely smooth... no stumbling or stalling.

In neutral the engine responses as it should, easily achieving 4000+ RPMs upon throttle engagement.

We thought shifter cables? Not sure because in neutral the engine responds.

These items lead me to believe something to do with prop/drive - whatever is accepting the power provided by the engine.

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2008 278 Vista | 8.1 Gi Volve Penta
Mark II C Touring Zodiac w/9hp outboard

Only recent change was to oil - used 25w-40 Sierra Premium Blend Marine oil that our marine mechanic said to use.

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2008 278 Vista | 8.1 Gi Volve Penta
Mark II C Touring Zodiac w/9hp outboard