Propeller Trim Tab Confusion

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
whalerron
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Joined: Sun Mar 06, 2016 8:31 pm

Propeller Trim Tab Confusion

Postby whalerron » Tue Apr 06, 2021 9:52 pm

Many years ago, there was a discussion here in the GAM forum about propeller trim tabs. Here is a link to that discussion http://continuouswave.com/ubb/Forum1/HTML/021079.html

That discussion included quite a bit of technical detail about why a propeller trim tab is needed on an outboard motor. On Yamaha outboards, until recently, a propeller trim tab has always been original equipment and it doubles as an anode for the lower unit. The propeller trim tab on my 2004 225 hp Yamaha 4 stroke outboard has deteriorated and when I bought a new propeller trim tab, the new one didn't have a fin on it. The new part is simply a domed anode that fits where the propeller trim tab had been. I have contacted three dealers, and each told me that the propeller trim tabs for all Yamaha V6 outboards have been superseded by the new fin-less units.

For my motor, the original finned propeller trim tab part number 61A-45371-00-00 is no longer available and it is superseded by part number 6CE-45373-00-00 which is a fin-less part.

When I visited the Yamaha webpage, I saw that, indeed, all of their V6 and larger outboards use the fin-less propeller trim tabs. This surprises me because my boat steering is very noticeably affected by the finned propeller trim tab. When the tab is incorrectly adjusted, my motor is harder to steer in one direction than the other.

I guess that Yamaha has decided that the old motors no longer need propeller trim tabs.

What has changed with the newer motors to allow them to operate correctly without finned propeller trim tabs?

If nothing has changed, were these trim tabs ever really needed on the larger Yamaha outboards?

jimh
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Re: Propeller Trim Tab Confusion

Postby jimh » Wed Apr 07, 2021 7:28 am

The element of the outboard engine that has changed, particularly with larger engines like a V6 engine, is the use of hydraulic steering. There is no feedback at the helm steering wheel from propeller torque with hydraulic steering, whereas with mechanically linked steering or wire-rope-and-pulley steering there will be.

Also, propellers with high blade rake angles are more common now, and having a trim tab projecting into the propeller aperture space would create interference with the propeller blade rotation.

But those are just possible causes. Maybe Yamaha just wanted to carry a one-size-fits-all part.

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Phil T
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Re: Propeller Trim Tab Confusion

Postby Phil T » Wed Apr 07, 2021 9:33 am

I think you have the wrong version.

The flat annode is for twins or engines with hydraulic steering.

Call Andy at SIM Yamaha. They will get you sorted.

https://www.simyamaha.com/search.php?search_query=61A-45371-00-00%20&section=product
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