Proper Trim

[mikeroe]

I have an '89 Tracker 1800FS with a Johnson GT 150 motor. My problem is porpoising. I Have to trim the motor all the way in to get up on plane. If I try to trim out any at all she starts porpoising real bad. The previous owner put the 150 on it. He got with a 115. He also added a hydro-foil to help with the porpoising. I was just wondering if, even though it's rated for a max of a 150, if the additional weight would tend to make this boat overly stern heavy. I like the power of this motor but if this is the case I may go back to a 115.

 

[CWKboat]

Re: Proper Trim

I have an '89 Tracker 1800FS with a Johnson GT 150 motor. My problem is porpoising. I Have to trim the motor all the way in to get up on plane. If I try to trim out any at all she starts porpoising real bad. The previous owner put the 150 on it. He got with a 115. He also added a hydro-foil to help with the porpoising. I was just wondering if, even though it's rated for a max of a 150, if the additional weight would tend to make this boat overly stern heavy. I like the power of this motor but if this is the case I may go back to a 115.

Sounds like the motor is sitting too high on the transom. Do you have a jackplate? If not, I would suggest lowering the motor one hole at a time and see if this remedies the problem. It's trial and error to find the best setting.

I have a manual jackplate on my boat, so at one point did have to lower the motor after I had raised it too high and was experiencing similar symptoms.

If it's porpoising, you also have the issue of potentially overheating the motor if the water pump pickup isn't getting enough water, so I would try to lower it one hole at a time and see what happens from there.

 

[Another retired guy]

Re: Proper Trim

The quick check for correct motor height is to see where the anti-cavitation plate is in relation to the keel. Position the motor so the plate is level - it should be in line with the keel. Can be 1/2" higher, but no more.

 

[mikeroe]

Re: Proper Trim

Well this added whole other set of issues. I just measured the cavitation plate / keel and the bottom of the plate is 3/4" above the keel. The bad part is the motor is as low as it can be set. I'm thinking a jack plate is needed?

 

[Another retired guy]

Re: Proper Trim

Well this added whole other set of issues. I just measured the cavitation plate / keel and the bottom of the plate is 3/4" above the keel. The bad part is the motor is as low as it can be set. I'm thinking a jack plate is needed?

3/4" is not too bad - not ideal, but before buying a jack plate have you tried trimming the boat by moving some weight forward?
You may also want to try it without the hydrofoil.

 

[mikeroe]

Re: Proper Trim

The only weight I have aft is me. with the boat on the trailer I leveled the boat. I noticed when I set the trim all the way in the motor was almost straight up and down. Shouldn't it be at an angle in? I had planned on removing the hydro-foil for my next time out.

 

[Texasmark]

Re: Proper Trim

My engine is more like 1 1/2 inches above even, no setback, no jack plate. Engine is 1 notch up. Runs just fine. SS Ballistic prop.

I think you nailed it with the added weight. Usually you can power your way through porpoising but there are limits. Other thing is that hull might have a hook in it which can cause the problem.

In your case is it a problem hole shooting tucked in? If that bad maybe trim tabs are in order.

Mark

 

[mikeroe]

Re: Proper Trim

Maybe I'm "tilting at a windmill" on this issue. After the last post Texasmark I got to thinking. From a dead stop the boat will get up on plane pretty fast with the trim all the way in and runs pretty good just like it is. I noticed today while cruising at 30mph, with the trim in I was trimmed the way it should be running and the motor was running without sounding strained .My OCD mind keeps get hung up on the trim gauge. I guess I need to ignore that and just listen to the boat.

 

[Texasmark]

Re: Proper Trim

Maybe I'm "tilting at a windmill" on this issue. After the last post Texasmark I got to thinking. From a dead stop the boat will get up on plane pretty fast with the trim all the way in and runs pretty good just like it is. I noticed today while cruising at 30mph, with the trim in I was trimmed the way it should be running and the motor was running without sounding strained .My OCD mind keeps get hung up on the trim gauge. I guess I need to ignore that and just listen to the boat.

Sounds like a plan. All the gauge is for is to tell you where it is, not how to use it....the trim. You're using your head on this man. Great idea. Maybe you'd be better off just masking tape over the gauge. Grin. If you want to know where the engine is, do as I do and take a quick peek over your shoulder. Good luck.

Mark