Is There a "Best" Engine Angle With a Permatrim?

[Writer_Ron]

Now that I've added a Permatrim to Muse's Honda 150 -- and actually tried the thing -- I'm wondering if roughly horizonal is the best engine angle. I ask because small trim changes increased/decreased speed (keeping engine RPM constant).

This means that small engine-angle changes increase/decrease PT drag -- no great surprise.

The trim sweet spot at 4500 RPM was a slightly negative needle. For the record, my prop is a shiny, new stainless steel Apollo: 14.4 x 15.

I've searched, but haven't found any recommendations.

 

[localboy]

I have no idea. The entire "to Permatrim or not" debate is a hot potato for me and I vacillate between yes...and no...

 

[colobear]

I think there is a technical answer relating to the angle between the permatrim and (something else, I cannot remember). For us, we simply move the engines up and down depending on speed, water conditions, boat load, etc. For us there is no one spot that is always the "right" one.

 

[Dreamer]

For us, about 3 bars up on the Honda Digital gauges is a good start. If the water is exceptionally smooth, another one or two bars helps. Watching the gallons per hour and the speed carefully will disclose the "sweet spot". Of course, load in the boat factors in too..

 

[Will-C]

Every boat is a little different because of the way they are loaded, hull designs etc. I start off with engine trimmed all the way down. When it bottoms out it makes a different sound,then I bump it back up with a couple quick touches on the up trim. Thats where I begin. If you are running along on plane you can adjust the trim till the speed increases or slows down to find the sweet spot. I like to run our engine in the 3500 to 4000 rpm range as it get decent fuel mileage there. Different sea conditions call for different adjustments to you engine trim. Running into a head sea I would trim down the motor some to keep the bow down. In a following sea i would trim the engine up to keep the bow up a little and to ride on the back side of the swells especially when coming into an inlet. Experiment with the trim button the boat will talk to you.
D.D.

 

[Writer_Ron]

Experiment with the trim button the boat will talk to you.

That seems right. I'll play with trim at different RPMs (and sea conditions) and make up a table of starting-point trim angles.

Thanks for all the feedback.

 

[thataway]

All good suggestions--but none of the posters have a C Dory 25 with a 150 Honda. The Permatrim should run just at the surface of the water. Its function is to put the bow down into chop. To get the proper running, you may have to move the engine up or down a hole or two. If you are looking for the most effecient running, then where the RPM is the highesst, wiht highest boat speed, and same throttle setting.

We had a C Dory 25 with a Honda 130 (That and a Suzuki 140) are slighly underpowered. The Permatrim gives stern lift and improves planing, as well as improved handling in a chop. The 135/150 Honda and other 150's on up, tend to not need as much stern lift, unless they are very heavily loaded.

 

[Writer_Ron]

All good suggestions--but none of the posters have a C Dory 25 with a 150 Honda. The Permatrim should run just at the surface of the water.

This of course is when the boat is up on plane -- which I found decidedly tricky to view.

I believe that an alternative (out-of-the-water) mounting "height" is to position the Permatrim at roughly the same level as the Bennett trim tabs. If so, my prop may be a tad too deep. I'll have our local dealer correct it during the next 100-hour servicing.

I understand that water flowing over the top of the PM impacts performance. But even if this is happening, there should be an engine trim angle that maxes lift and mins drag.

 

[Hunkydory]

I understand that water flowing over the top of the PM impacts performance. But even if this is happening, there should be an engine trim angle that maxes lift and mins drag.

Ron, ideally the Permatrims would be aligned with the bottom of the boat & acting as an extension of it with the hight as Bob said, set to create the least drag & most efficient contact with the water.  In reality the position of the Permitrims  in conjunction with the prop angle is important only for the end goal  of making the bottom of the boat best align with the water to make it as efficient & the ride the most comfortable as possible.  To accomplish this as many have stated, there is rarely any set position that will accomplish the goals intended,  just to many  changing variables involved.  I stated on a previous thread on this subject that for me the best set up was just aligning the Permatrims with the boat bottom & using the trim tabs for the boat angle desired for comfort ability  & efficiency.   Now after more than a month of running here in Alaska with huge variances in weight distribution, I have like most others here found a general starting point to go from, but no constant that works all the time.    For me they do the job as advertised & I'm very satisfied with their addition to the boat.

Jay

 

[Writer_Ron]

Now after more than a month of running here in Alaska with huge variances in weight distribution, I have like most others here found a general starting point to go from, but no constant that works all the time.    For me they do the job as advertised & I'm very satisfied with their addition to the boat.

I began the kind of "fine tuning" you're talking about on my first time out with our new Permatrim. As I said, I'll take the time to develop an engine trim table that gives me different engine angle "starting points."

I thank all for the additional input.