The OFFICIAL TomCat Permatrim BEFORE AND AFTER thread!!

[Captain Starbucks]

I wanted to lower my planing speed as much as possible. I operate almost entirely in the ocean in the PNW and conditions aren't always favorable for using the TomCat's legs. I knew at the end of last year, I was either going for new stern lifting props, or Permatrims, or both. After several conversations with Ken at PropGods, he talked me into trying the Permatrims first, and I'm sure glad I did.

Anyways, last fall prior to storing for winter maintenance, I thought I'd get some baseline data. To be perfectly clear, the conditions before and after weren't identical but I'll try to line out the differences as much as possible (noted in the image below).

I'm a bit suspect of the GPH figure on the With Permatrim side at the 4,000 rpm point. I'll have to double check that next time I'm out.

A few things of note: The boat was 300 lbs or maybe more lighter on the With Permatrim side. Also, the water had a slight ripple on it on the With Permatrim side. Ripple has a great drag reduction factor, ask any floatplane pilot.

[thataway]

Thank you and interesting take. I had a 2006, TC 255, with the Suzuki 150s. Stern lifting props (4blade), SS. I also added the Permatrims to attempt lower the planing speed, and cruising speed in semi displacement mode. I don't remember doing as an exhaustive analysis on the RPM/Speed, fuel consumption. (My impression was that the fuel gauge/flow meters were not that consistent--I was pulling data off the turbine type of gasoline flow meters, not the engine computers.

My impression was that the Permatrims threw a bunch of water up, on the sides/at speeds in the 9 to 10 knot range, Almost to the point I considered it possibly dangerous.

I also got lower high end speed, and decreased fuel use at the higher speeds. What makes your fuel/speed somewhat "suspect" (not being disrespectful, but wondering if other factors were in play????). Because most folks who use Permatrims find that the higher end they have a slightly increased drag and slightly raise the fuel consumption--many have found that they cannot achieve the same high end speed at WOT. (My WOT were at 6,000 RPM and very close to what yours are at 5700 RPM, which is exactly where you want to be with the Suzuki (Different gearing and using considerably greater pitch props--my recollection was I was running 21" pitch props. I had two sets one at 19 the other at 21. I rarely got over 2 mpg. An exception was where I ran almost 200 miles at a constant speed "Best efficiency" run. I am sure my boat was heavier than yours, with extra batteries, Honda Generator, full fuel tanks, full water tanks, etc.

So I am interested in if you sustain these numbers over longer distances, and longer periods of time, running two ways over the same course--distance, etc. I understand that GPS will give us numbers without having to use a measured mile--but GPS gives us speed by position and can be different that speed thru the water. This is why I like to use a measured mile, both ways. to get my most accurate mile.

I don't know if you were using the engine computer for "mileage" or an external Lawrence, like I was using. How did you determine you had 18 or 17 gallons of fuel in each tank? That is just to "pat" a number.i??

There are just so many variables.

Again, Thanks

[cmetzenberg]

I ditched my permatrims on my tomcat. I don't notice much of a difference. I'd be interested in adding a foil wing between the hulls aft to create lift....if there was such a thing off the shelf.