Adjusted my trim, now the boat pulls right.

[bdm26]

Hi All-

This summer I got myself a mid '80's 35HP Merc tiller which has been a welcome upgrade from the 7.5HP Merc I had before on my 14' Lund.

When I first put it on I wasn't sure how high/low to set the trim with the pin, so I picked a spot in the middle and gave it a shot. After running around like that for a few trips, I felt like it was to high and needed to be down a bit. I reasoned that because when the boat would get on plane the lower unit/prop was no longer perpendicular to the water and was "pushing down" if you will vs forward when on plane.

So when I had it out of the water again I adjusted it so the lower unit/prop would be more perpendicular to the water when on plane. Issue now is the tiller wants to pull left out of my hand as we are cruising (thus turning the boat right). I'm not sure how adjusting the trim has anything to do with this which makes me think its related to something else but honestly I don't know where to start.

Any help would be great and if I'm going at this trim thing wrong please call me out on it, I want to get it right.

Thanks!

 

[kemer1]

Re: Adjusted my trim, now the boat pulls right.

I think you may be on the right path with this trim thing. I had a 18 foot bowrider with an I/O and obviously power trim. When I would trim up too high I would also feel a tug at the wheel and it would want to turn on me (no power steering). So that's how I knew when I went too high, then I would blip it down till it tracked straight and that was that.

 

[svxtech]

Re: Adjusted my trim, now the boat pulls right.

Do you have an anode under the cav plate above the prop? might need to be adjusted/tightened

 

[jacoboregon]

Re: Adjusted my trim, now the boat pulls right.

You may want to do a search for 'prop steer', prop torque', or 'outboard steering torque'. you'll find a lot of useful information. Have you tried adjusting the trim tab on the ventilation plate? adjust it in the direction you notice the torque, (which i believe in your case would be to the right/starboard, if I understand correctly it turns easier to starboard).

When on plane, the ventilation plate should be at water level, and the bow should be up some without porpoising so the bow doesn't dig in when turning, which can happen if the trim is set to close to the transom and the boat runs too flat on plane.

 

[smokeonthewater]

Re: Adjusted my trim, now the boat pulls right.

I suspect that you are now trimmed too low and the bow is plowing causing your steering problem.... You want to try the trim in various positions until you find the best speed without porpoising. AFTER that adjustment you then adjust the trim tab for neutral steering at the speed you most often run.

BTW no the engine does not need to be exactly perpendicular to the water surface....

 

[KDAVID1]

Re: Adjusted my trim, now the boat pulls right.

I suspect that you are now trimmed too low and the bow is plowing causing your steering problem.... You want to try the trim in various positions until you find the best speed without porpoising. AFTER that adjustment you then adjust the trim tab for neutral steering at the speed you most often run.

BTW no the engine does not need to be exactly perpendicular to the water surface....

+1. Typically when you are trimmed correctly--you get zero torque. Below and you get alot of torque.

 

[bdm26]

Re: Adjusted my trim, now the boat pulls right.

Do you have an anode under the cav plate above the prop? might need to be adjusted/tightened

I do...did have an anode on the cav plate. I went out to look and sure enough its missing. I know it was there when I bought the motor and looking back on it, it was loose and just spun!

Going by your suggestion, I was wrong in assuming that was normal.:facepalm:

The good news is I found it here for a price that I can swallow (although out of stock, so more searching is required): http://www.marineengine.com/newparts/part_details.php?pnum=MER31640Q+4&ptype=&Engine=&Model=

Included two pictures for some evening painful laughs. I am hoping that this is all the pulling issue is. I am going to order the replacement and hope it gets here soon enough to get the boat out one more time to see if that corrects the issue before I have to wait for spring. In the mean time, I am going to do some googling on the other terms talked about here to become more familiar with them.

 

[bdm26]

Re: Adjusted my trim, now the boat pulls right.

I just have to add...I can't understand how I missed that damn thing not being there when adjusting the trim.../sigh Can't help but chuckle to one's self.