Home made trim tab on motor make sense?

Petesafloat

Recruit
Joined
Feb 6, 2014
Messages
3
So I'm brand new to this forum and back owning a boat after half a century away. I bought a 1987 aluminum "bass" boat. 15' poor mans' model. It came with a 1987 35 hp Force outboard. Runs quite well, but pulls right firmly at speed. Problem is, it has no trim tab on motor. The exhaust snout is asymmetrical. Starboard side is cut back farther than port. I assume it was designed to use uneven exhaust direction to compensate for motor rotation. If so, I hope the design team left to find another avocation. After much Google searching, and discarding discussions about adjusting a (non-existent) trim tab and changing the mounting height of motor on transom (quite impractical), I am thinking about installing my own trim tab(s) on cavitation plate. It is already drilled for a pair of hydrofoil fins. I'm thinking of experimenting using a 4 or 5" piece of 1" aluminum angle mounted on the plate. Possibly a piece on both sides of the lower unit. Anyone ever done this or thought of what possible problems might be encountered?
 

pnwboat

Rear Admiral
Joined
Oct 8, 2007
Messages
4,251
Re: Home made trim tab on motor make sense?

I don't know about your 35HP motor, but on my 125HP motor, the exhaust snout is the trim tab. The bolt that holds the trim tab on goes through an elongated hole. Loosen the bolt and you can move the trim tab to port or starboard.

If the exhaust snout is not moveable, then I guess you could try experimenting with different size pieces of aluminum angle.
 

MickLovin

Master Chief Petty Officer
Joined
Feb 18, 2013
Messages
822
Re: Home made trim tab on motor make sense?

What pnwboat said, it's a snout which you probably just need to move to centre or if it is centre try turning the front of the snout as you are looking at it to the left to compensate for it pulling right.

24.jpg
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,923
Re: Home made trim tab on motor make sense?

Your snout might not be adjustable.
Post a pic of the lower unit and show the tab in a couple of views.
If it is adjustable,from the rear, if the boats turning right?
Move the tab to the right.
If it's still a problem?
You can add strips along the bottom of the boat,kinda like a rudder.
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: Home made trim tab on motor make sense?

The exhaust snouts on almost all years of 35-50 HP Force engines (before Mercury lower units.) were never adjustable. The removable snouts were a zinc anode and can not be welded or soldered. HOWEVER: If you drill and tap two holes through the right side and attach a bent aluminum plate it should be sufficient. Bend the plate to the right until you get straight steering at whatever throttle setting you normally use.

Make the plate about the same width as the height of the exhaust snout and extend it about an inch past the rear. That should be good but you will need to play with it until you get what you want.

I would not use the existing holes in the anti-ventilation plate because I suspect there might be some interference with exhaust, prop, or water flow. Besides, the off-center mounting offends me aesthetically. LOL.
 
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