Right Turn - Normal?

[Blue Mesa]

I'm new to this whole deal, so forgive me if this is a really stupid question. I recently inherited a 14' aluminum boat with a 1981 25 hp Johnson. It runs great, but above about half throttle it has a strong pull to the right. Is this from torque? Is this normal? Or, is there some way to trim it out?

Thanks for any help you can offer.

 

[tmcalavy]

Re: Right Turn - Normal?

There should be a small shark-fin on the lower unit of the outboard. Not the skeg below the prop, but up higher. Those little fins that I can't recall the name of for some reason, are adjustable to keep the boat from pulling one way or another. Yours probably needs adjusting or may be gone altogether.

 

[Blue Mesa]

Re: Right Turn - Normal?

That's interesting. I guess you are talking about a vertical "shark fin" there. I went out and looked, definitely no other fin but the skeg below the prop. Also, no place that looks like something is missing or broken off.

Is this something I can replace? Where exactly would it mount?

 

[Blue Mesa]

Re: Right Turn - Normal?

Ok, I've been reading a bit about trim tabs. If this motor ever had one, it's gone. Again, this is a 1981 motor, and a tiller, not a wheel. Should it have a trim tab?

 

[MikDee]

Re: Right Turn - Normal?

I'm new to this whole deal, so forgive me if this is a really stupid question. I recently inherited a 14' aluminum boat with a 1981 25 hp Johnson. It runs great, but above about half throttle it has a strong pull to the right. Is this from torque? Is this normal? Or, is there some way to trim it out?

Thanks for any help you can offer.

So what else is new, Steering Torque! rears it's ugly head.
There should be a mini trim tab mounted to the bottom of the Cavitation plate at the back, movable by loosening a cap screw through the upper housing of the Cav. plate to help with steering torque.
Here's my sticky: http://forums.iboats.com/showthread.php?t=250928

 

[dlngr]

Re: Right Turn - Normal?

The smaller Johnsons don't have this trim tab,also called a zinc anode...
I had the same problem with steering my 35hp .You can tighten the friction where the engine turns,so it doesn't move so easily,then you just have to put more pressure on the tiller to steer. My solution was to add remote controls and steering wheel.

 

[Blue Mesa]

Re: Right Turn - Normal?

The smaller Johnsons don't have this trim tab,also called a zinc anode...
I had the same problem with steering my 35hp .You can tighten the friction where the engine turns,so it doesn't move so easily,then you just have to put more pressure on the tiller to steer. My solution was to add remote controls and steering wheel.

OK, I was wondering if that was the case because there is just no place for this thing to have been bolted. I wouldn't have been surprised to find that my father-in-law had removed it at some point, but it doesn't look like it was ever there.

I ordered a manual a couple of weeks ago. I figured if it had a trim tab the manual would show it, but I still haven't received it.

Thanks

 

[jbjennings]

Re: Right Turn - Normal?

I was curious about your torquesteer problem so I checked the crowleymarine diagrams for an '81 25hp and it doesn't seem to have a moveable trim tab like I expected. It showed a split half lower unit which suprised me. I didn't think they still made the split lower unit in '81.
Therefore, the only thing I can think of is you have something bent on your lower unit. Is the skeg twisted? Is your motor in the exact center of the transom? Is your prop bent? I don't think a bent prop would cause it, though. It's a mystery to me, but I'd fix that since torque steer is very dangerous to me.
Good luck,
JBJ

 

[wbeaton]

Re: Right Turn - Normal?

The 1981 25 hp never had the anode the others have mentioned. That was only available with thru-hub exhaust lower units and not all of them had it. Tighten up the steering friction. If nothing is bent or damaged including the prop then its just torque steer.

 

[Whoopbass]

Re: Right Turn - Normal?

I had the same motor and every now and then would it pull hard to the right for a trip or two and and then it wouldn't for the next several trips.
I'm not sure why it did this. Maybe it was the way I had the boat loaded but it sure sucked. It would wear me out.
If it does this all the time maybe if you moved the outboard slightly to the left it would even it out but I might be wrong.

 

[reelfishin]

Re: Right Turn - Normal?

Do you have any holes or chips off the anti cavitation plate?
Look closely at the angle of the motor on the transom. I had a 1973 25HP that I used to run on a curved transom aluminum 15' boat, I kept the motor in the garage, off the boat, and if I wasn't careful about how and where I rehung the motor it would increase the torque steer. If it wasn't dead center and perfectly level it would pull hard to one side. I had another motor, an older Mercury that pulled hard due to a chip off the corner of the anti-cavitation plate. I ran it like that for years till finally making a patch plate and welding it on.

 

[Blue Mesa]

Re: Right Turn - Normal?

Thanks for all the ideas. I didn't put the motor on, it was already on the boat. I will measure to see if it is dead center. The prop looks fine. And I haven't seen any cracks or chips.

My father in law did extend the size of the horizontal fin above the lower unit. Is that the cavitation plate? He used a very thick plastic, and bolted it over the stock plate. I think he said he did that to make the boat plane better. I'm very new to this, so I don't know if that was either necessary or a good idea. He likes to tinker with things. I have to say the boat does plane well. I believe it is set on the second to the lowest hole on the bracket that adjusts the tilt. Sorry, I don't know all the terminology here. I can't wait to get the manual so i can read up on some of this.

Other then that, my guess would be some of it is natural torque, but maybe the motor is off center too. I'll check it tomorrow.

It doesn't feel dangerous to me, just annoying. I guess if I fell overboard, or lost the ability to hold the tiller for some reason, it could be an issue, but barring that, it just doesn't feel as balanced as I would think it could.

I keep editing this post. i was just looking at the hydrofoils for sale on iBoat. That is exactly what my F-I-L did to this motor. I think his is home made, but after seeing some of the manufactured ones, he may have actually purchased it and installed it. Apparently that's not unusual. But then I guess you all knew that already.

 

[reelfishin]

Re: Right Turn - Normal?

Try it without the hydrofoil.
Some factory made hydrofoils offer additional trim tabs to eliminate torque steer as well but anything you add will also take away top speed.
I would consider a bit of torque steer normal, but too much will get tiring after a long day on the water. A 14' aluminum boat with a 25hp motor shouldn't need any help getting on plane. I ran a 15hp on a flat bottom 14' for a number of years and would get 24 mph out of it. A 25 hp on a 14' should just about fly.

Got any pics of the set up?
(Lower unit pics, motor relationship to transom, mounting height etc.)

 

[Blue Mesa]

Re: Right Turn - Normal?

Try it without the hydrofoil.
Some factory made hydrofoils offer additional trim tabs to eliminate torque steer as well but anything you add will also take away top speed.
I would consider a bit of torque steer normal, but too much will get tiring after a long day on the water. A 14' aluminum boat with a 25hp motor shouldn't need any help getting on plane. I ran a 15hp on a flat bottom 14' for a number of years and would get 24 mph out of it. A 25 hp on a 14' should just about fly.

Got any pics of the set up?
(Lower unit pics, motor relationship to transom, mounting height etc.)

no pics, I can get some. I did move the motor about an inch to the right to see what that does. Again, I can live with it anyway, but it would be great to get rid of the turn.

25 mph? I can only get about 16, that's with my wife and I and a bit of gear. The motor seems to run well, but I have nothing to really compare it to. I do wonder if it will need to be re-jetted. My f-i-l lived at about 5000', I live at 8000'. But that's a question for a different thread.

 

[jimmbo]

Re: Right Turn - Normal?

Part of the right turn thing is due to the trim of the engine. Trimming the engine in will cause the engine to want to steer the boat to starboard, trimming it out will reduce that pull, further outward trim will eventually cause a pull to port. It has to due with how the effective pitch of the prop changes due to a different angle of attack unless the propshaft is parallel to direction of travel

Another part is Newtons 3rd law 'for every action there is an equal and opposite reaction'. Looking at the engine from above. When running the flywheel will be spinning clockwise, thats the action, the the opposite reaction is the rest of the engine is going to try and rotate counterclockwise. When the ouboard piivots in that direction it will steer the boat to starboard(right). Friction in the steering system and/or your arm on the tiller prevent it

 

[jbjennings]

Re: Right Turn - Normal?

You should get better than 15 or 16mph. Is that on GPS?? Even with a decent load that 25 should give you 22 or 23mph with a 14' aluminum boat.

BTW, I get 25mph with a '57 18hp on a light aluminum boat by myself, and about 21 or 22mph with my 250lb. father, 2 shotguns, goodies, etc. with the same 18hp. My '56 15hp with lots of wear goes about 21mph with just me.
Just to give you an idea. My dad's brand new yamaha 25hp went 27mph on a 14 foot aluminum boat with both of us in it and just a little gear. All GPS measurements of speed.
Just my opinion,
JBJ

 

[Blue Mesa]

Re: Right Turn - Normal?

You should get better than 15 or 16mph. Is that on GPS?? Even with a decent load that 25 should give you 22 or 23mph with a 14' aluminum boat.

BTW, I get 25mph with a '57 18hp on a light aluminum boat by myself, and about 21 or 22mph with my 250lb. father, 2 shotguns, goodies, etc. with the same 18hp. My '56 15hp with lots of wear goes about 21mph with just me.
Just to give you an idea. My dad's brand new yamaha 25hp went 27mph on a 14 foot aluminum boat with both of us in it and just a little gear. All GPS measurements of speed.
Just my opinion,
JBJ

See, that is good to know. I am new to this and have no frame of reference. The boat seems to move right along to me, but my hand-held GPS says 16, or it did the first day out. I have made a few changes since then.

I am going to remove the hydrofoil and see what that does. The boat is painted and does need new paint. The bottom is somewhat rough. I may fool with the trim a little, but from what I can read that seems close.

I do wonder if the motor is running rich at this altitude. I think I will try to get some pictures of the motor set up for you guys to look at.

I really appreciate all the help.

 

[Blue Mesa]

Re: Right Turn - Normal?

Here are a few photos of the motor set up. The first pics show it as I have been running it, with the hydrofoil and set on the lowest tilt setting. The last ones show it the way it is now. I have removed the hydrofoil, and moved tilted the motor out one notch.

What I noticed: The hydrofoil/anti-cav plate is a little over 2 inches below the bottom of the boat - Is that too low?

With the motor on that lowest tilt notch, it it is well beyond level - pointing up (pushing the bow down).

Even after moving it up a notch, it is still going to push the bow down some.

I thought this was probably as much as I should change until I get to try it, but I would really like some opinions here. i don't know why my father in law set it up that way, and I don't think he would remember at this point. So tell me what you see.

 

[reelfishin]

Re: Right Turn - Normal?

Here are a few photos of the motor set up. The first pics show it as I have been running it, with the hydrofoil and set on the lowest tilt setting. The last ones show it the way it is now. I have removed the hydrofoil, and moved tilted the motor out one notch.

What I noticed: The hydrofoil/anti-cav plate is a little over 2 inches below the bottom of the boat - Is that too low?

With the motor on that lowest tilt notch, it it is well beyond level - pointing up (pushing the bow down).

Even after moving it up a notch, it is still going to push the bow down some.

I thought this was probably as much as I should change until I get to try it, but I would really like some opinions here. i don't know why my father in law set it up that way, and I don't think he would remember at this point. So tell me what you see.

Your motor is too low, too long, the anti cav plate should be about 1 to 1.5" above the bottom of the boat. Never below it. A longer motor will create drag and that hydrofoil is probably just plowing water that low. Removing it will help but you will either need to find a shorter motor or build or buy a jack plate to make it right.

I have that same motor, I last had it on a 15' aluminum boat and ran it with the pin in the second hole from the transom, no hydrofoil.

On my old 14' boat, I had tried several set ups, the motor was a Yamaha built Mariner 15hp. When I got it it had a problem of over revving at top speed, I increased the pitch but had trouble getting on plane as fast, so I added a hydrofoil as an experiment. The hydrofoil took off 8 mph, the prop increase lost me about 400 RPM but didn't stop it from blowing out the prop. With the original set up, I could get as much as 31 mph lightly loaded. Fully loaded, with the higher pitch prop and hydrofoil got me about 23 mph. I eventually just put all back the way it was and lived with the fact that I just couldn't run wide open throttle without some weight in the rear. It was stick steer, so with just me in the boat, it was a bit rear light. A rear passenger would actually help it and I could run all out if needed.
I eventually hung a 35hp on that same boat, I didn't gain much speed, but gained gobs of acceleration. I got 36mph, but it shot out the hole like a rocket and sucked down three times the fuel. The added weight of the extra fuel I needed to get to where I fished actually made it slower. If I could have run with less fuel, it would have really flown. I had to carry 18 gallons of gas rather than only 6 to make it there and back. I didn't keep it long after that. I had found a larger boat and had all but stopped using that boat soon after.

I wish I had it back with the 15hp with the price of fuel these days though.

 

[Blue Mesa]

Re: Right Turn - Normal?

Your motor is too low, too long, the anti cav plate should be about 1 to 1.5" above the bottom of the boat. Never below it. A longer motor will create drag and that hydrofoil is probably just plowing water that low. Removing it will help but you will either need to find a shorter motor or build or buy a jack plate to make it right.

I have that same motor, I last had it on a 15' aluminum boat and ran it with the pin in the second hole from the transom, no hydrofoil.

On my old 14' boat, I had tried several set ups, the motor was a Yamaha built Mariner 15hp. When I got it it had a problem of over revving at top speed, I increased the pitch but had trouble getting on plane as fast, so I added a hydrofoil as an experiment. The hydrofoil took off 8 mph, the prop increase lost me about 400 RPM but didn't stop it from blowing out the prop. With the original set up, I could get as much as 31 mph lightly loaded. Fully loaded, with the higher pitch prop and hydrofoil got me about 23 mph. I eventually just put all back the way it was and lived with the fact that I just couldn't run wide open throttle without some weight in the rear. It was stick steer, so with just me in the boat, it was a bit rear light. A rear passenger would actually help it and I could run all out if needed.
I eventually hung a 35hp on that same boat, I didn't gain much speed, but gained gobs of acceleration. I got 36mph, but it shot out the hole like a rocket and sucked down three times the fuel. The added weight of the extra fuel I needed to get to where I fished actually made it slower. If I could have run with less fuel, it would have really flown. I had to carry 18 gallons of gas rather than only 6 to make it there and back. I didn't keep it long after that. I had found a larger boat and had all but stopped using that boat soon after.

I wish I had it back with the 15hp with the price of fuel these days though.

Thanks for the input. Could you check out the other thread I started on set up? It describes what I experienced when I took off the hydrofoil and raised the motor a bit. I'm a little confused about what is going on here.