Replacing the motor's trim tab question

[SmokyMtnGrady]

Hey yall:
I lost my trim tab in the Keys and suspect when they rebuilt my motor or when I did the 20 hour power head service it was loosened and it just rattled off. I got my boat back tonight after my brake system was replaced on it. I put the new tab on the motor without a problem. I have couple questions....the prop spins to the right which cause a small steering torgue to the right? Correct?

So, when I put the tab on motor and you see the tick marks and center mark on the anticavitation plate, I put the tab so it angles slightly to the left to counter this torque. Is this correct? As an aside, I honestly did not feel or notice the steering torque induced by the prop after I lost the tab. I know it serves dual purposes for the trim function plus as sacrificial annode so it is important to have.

 

[seabob4]

Single engine? With the motor tilted up, looking at the torque tab, the trailing edge should be at 1:00....

 

[SmokyMtnGrady]

Seabob, thanks! Yes, single engine and I will adjust it. I have it at 11....

 

[seasick]

If you remember that the trim tab adds drag in the direction is is turned, you will get the adjustment correct. The tab doesn't create thrust, its adds drag, so if the vessel tends to steer to starboard, you adjust the tab to starboard. The extrag drag counteracts the tendenct to steer to starboard.

 

[SmokyMtnGrady]

I thought it functioned like a tiny "engine rudder" to counter the torque of the prop spinning? I guess rudders do create drag in one direction like paddling and steering a kayak....I never thought of it in those terms....thanks for clarifying this...learn something new every day here..

 

[seasick]

I thought it functioned like a tiny "engine rudder" to counter the torque of the prop spinning? I guess rudders do create drag in one direction like paddling and steering a kayak....I never thought of it in those terms....thanks for clarifying this...learn something new every day here..

It took me a while to understand the concept and burn it into my head. I finally found a book with the explanation. It's funny but the 'logical' way to see it is as a rudder that redirects thrust. After messing around with tab settings and seeing the results, it makes sense now.
Enjoy..

 

[Capt Khaos]

Hello,
I read your post with great interest. I too have a 228 with an F250 and noticed the other day that my second trim tab/zinc was missing. The first time I thought the dealer screwed up during the 100 hour service but the second one I installed myself. I made very sure it was tight. The bolt was still in the hole so I reused it. Has anyone had this problem? What's up? Do I need Loctite?
Thanks,
Dan

P.S. I set mine in the center and it worked fine.

 

[seabob4]

Hello,
I read your post with great interest. I too have a 228 with an F250 and noticed the other day that my second trim tab/zinc was missing. The first time I thought the dealer screwed up during the 100 hour service but the second one I installed myself. I made very sure it was tight. The bolt was still in the hole so I reused it. Has anyone had this problem? What's up? Do I need Loctite?
Thanks,
Dan

P.S. I set mine in the center and it worked fine.

Sometimes they work fine that way. Each individual boat will be different...