setting trim pins.....

[bob johnson]

after posting about motor heights on another thread, I went out to really take a look at my set up..

I mounted a 10"set back hydraulic jack on my 20 ft mod V. then mounted a 1995 115 hp 2 stroke on that.

the motor has 4 sets of holes and the jack has two sets of holes on BOTH sides of the jack..

well i used the absolute heighest combo I could and it still doesnt get my cav plate above the bottom of the hull.....

AS THE TRIM PIN IS SET CURRENTLY

when trimmed all the way in...to pin setting hole #1 the cav plate goes way past parrallel with the bottom of the hull...and thus is actually at almost a 10 degree angle down from parrallel..

I have been using the boat all winter like that...I am not experiencing any negative effects that I KNOW OF!!

so i trimmed the motor out today and eventually when the cavitation plate IS PARRALLEL with the hull......it is dead even with the bottom of the hull!!!


but the motor looks like it is trimmed out maybe to PIN HOLE # 3, or #4

(there are 6 pin holes, set at 2 rows of three each one row above the other...)

SHOULD I set a pin at this spot that will not allow my trim to force the cav plate past parrallel???

I do not have issue with keeping the nose down...

mainly because i just have always trimmed IN until she stops..

some times for max speed Ill trim out and pick up maybe 3-4 MPH..

Trim is really only important to me under power, when :
1) the waves a rough and I want to get the bow way up, to keep them from breaking over it....and obviously i am not going that fast

2) when i am going as fast as i can on flat calm water..

all other times I am just planing, and or the water is too rough to go full speed.

here is a photo of the prvious motor I had mounted on the jack..a 90 hp ocean pro, but it is the exact same motor as the 115 ocean runner I currently have...these dont show how I mounted my current motor, but they show the holes for the trim pin.

thanks

bob

 

[Chris1956]

Re: setting trim pins.....

Bob, That picture shows the motor mounted all the way down on the jack plate. With the setback you have, I would mount it all the way up on the jackplate, and use the jackplate adjustment to set the height properly. You should be 2+ inches above the hull, with that setback, I would think. Observe the boat on plane to see how much above the water the AV plate is at plane speed. Watch for the water intake holes to be exposed. You can plug the top one, if necessary.

The tilt pin is a minor issue, since you have PTT. Set the pin on the most forward position, and forget it.

You are looking for max top speed, safe handling and correct waterflow to the motor, are you not? Concentrate on finding the correct height for these. Remember that if the motor is lower in the water, it has more drag, but will lift the bow better when you trim it. The optimum height is the one that gives you enough bow lift to reduce wetted surface, and still has the motor mounted high enough to minimize drag. This is likely different for each boat and load.

 

[bob johnson]

Re: setting trim pins.....

thanks for the reply...that picture was only to describe the pin holes... that was my previous motor, a 90 hp.. as i stated in the post.

the motor I am running now is a 115 and the motor is mounted as high as it can go...I can imagine Johnson making this motor without titl and trim, but the 6 sets of holes are there!!!

I was just wondering if people find there best trim spot and set a pin, so they can just peg the switch to get it 100% of the time, instead of monitoring the boats disposition to see if you are there!!!

I really dont want to play with the trim and jack all the time..

the jack was just a tool for shallow water motoring....

I wish there were a few extra mounting hole so i could raise the motor even more


bob

 

[Chris1956]

Re: setting trim pins.....

Bob, The best trim spot is different at different throttle settings. Generally higher RPM requires more trim for best performance. Minimum trim is for accelerating from idle. If you leave the motor all the way down, while at cruising speed, you are not maximizing speed, economy or handling.

However, it is your boat, and you may run it anyway you see fit.....