Permatrims on a CD25 with twins

D

Dora~Jean

Active member
Well I did it, ordered the Permatrims a week ago (Monday), on my doorstep Friday. I bit the bullet because I determined that my stern needed more lift than the trim tabs could do alone -- efficiently. Background: My boat runs best with the motors all the way down (negative trim) and with some trim tabs at 15-18 knots, my normal speed. If I trimmed the motors to neutral (i.e., AV plates parallel to the water flow), the boat was slower at the same throttle setting even after adjusting the trim tabs for maximum speed.

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More pictures in my album here.

I was pleasantly surprised on the quality workmanship and finish, right down to the near perfect color match to my Yamaha 80's. All the hardware (SS) was packaged well and the proper count. The instuctions are a bit weak, mainly a crude drawing, but adequate. I conversed a fair amount with the vendor by email on installation, performance expectations, and other technical details, he seemed quite knowledgeable -- another pleasant surprise. And most emails were on SUNDAY'S!

Took me about 2 hrs to measure, re-measure, position, re-position, mark, re-mark the holes on the first engine. Then 20+ minutes to drill that first HOLE, then about 20 minutes to drill 9 more -- a tip, drill the two end 1/8" pilot holes first, then 1/4" and insert bolts, that will mitigate any possible movement of the Permatrim while drilling the remaining pilot holes. An important note not mentioned in the instructions: After you remove the prop, cover the spindle and area with a plastic bag to keep the shavings out. I carefully cleaned the surfaces and applied a good bead of 3M 4200 (they recommend 5200, too permanent for my tastes), inserted the 1/4" SS bolts, washers and nylock nuts, torqued down to snug only, got to be careful with SS, it is fairly soft, the vendor pre-warned me.

Some downsides I came up with re this add-on: 1) More difficult to fish around, 2) More difficult to clear the prop of seaweed or other debris, 3) Will probably search out your knee when you least expect it while walking around your boat.

Upside, should improve gas mileage (efficiency), especially for twins. The true amount of difference will take some time to determine based on sea conditions and boat loading over the next several months. I plan to start with engines at neutral attitude, then inch them down when at speed (15-18 kts) until maximum speed vs rpm, then memorize that position. Will use the trim tabs only to balance the boat laterally if needed.

Stay tuned for data updates, I go to Catalina this coming weekend, but boat will be heavier than usual with scuba gear on board. Looking forward to try'm out!
 
I installed the Permatrim on my Yamaha 50 to power my 16'er. Couldn't imagine running with out it. There are no trim tabs on a 16. For the same reasons you mention I want to increase the lift on my 19'er which has trim tabs and is powered by a Honda 90.
I built a gig out of cardboard to aline the holes and to get the correct position on the cavitation plate for the Permatrim on the Yamaha. Came out perfect ( no other way :D ). I plan to do the installation the same way on the Honda. Wish me luck :wink:. I will watch to see how you like the performance on the twin 80's and the 25'er. I know my 16 didn't like bow down at higher MPH. Only slower in rougher water.
 
Steve,

One of the things that I did when I put the Permatrim on Constant Craving was to cap each of the stainless bolts with an acorn nut. Sooner or later, I expect that I will try to use the plate as a swim ladder and slice myself up, hence the acorn nuts.

By the way, your install looks great!

Steve
 
Thanks for the good words, I feel great now that it's over. I thought about acorns nuts too, might do that, but will try cutting off the bolts first then light grinding to smooth out, if doesn't work, the bolts should be about the right length for acorns then.

One other downside I forgot to mention, the Permatrims are almost 1/4" thick. This causes some interference with a normal socket and low profile 3/8" breaker bar to get to a couple of the lower end bolts. Might have to sacrifice and grind down a socket a bit just for that purpose.

I also plan to try various combos of engine trim while feeding some trim tabs (mine are oversize) and see if I can find some optimum settings. All of course depends on speed, sea state and boat loading, lots of variables. I have a 'before' speed vs rpm chart with specific loading, I'll try to duplicate that someday under the same conditions.
 
Hi Steve,

You will like the PTs. Will really get the bow down, will allow you to stay on plane a couple of kph slower, will give you some lateral trim without the trim tabs (trim tabs are better for this). I wouldn't go back.

Mark
 
Went to Catalina this weekend, now I have some data and impressions.

Short story: The Permatrims are KEEPERS.

Details: There was a VERY surprising, unanticipated, first thing I noticed when I got up to speed, 15-17 knots while still in the bay. It's like I installed Power Steering!!! I have hydraulic steering and twins, both CW rotation (had to go to 115hp min to get counter-rotating props), they have a fairly strong pull to starboard. I have the lower end trim tabs adjusted way over, about 30 degs each. With the Permatrims and their down-turned edges, they must really reduce that torquing effect. Other devices that have 'fins' will most likely perform similarly. But wow, steering is so effortless now, unbelievable. I think the hydraulic steering may outlast everything with so little pressure on it!

Going out I could only do 7-9 kts due to the waves and chop. I lowered the Permatrims (engine) about 1/2 way of total neutral to negative span. Then adjusted the trim tabs to adjust the attitude and side-to-side level. I'll get out there and measure the angles, might be easier to visualize.

Coming back, I adjusted them only slightly negative to provide a bit of lift, then again used the trim tabs to level and adjust attitude. Very nice, no porpoising or other behaviors, following seas -- no problem, no digging in. This was the first time I was able to run the engines at a nearly level attitude to the water flow, quite a difference. But the trim tabs are definitely needed as well to keep the bow down correctly.

Efficiency. I took some rpm vs speed measurements, they show a substantial increase in speed at every rpm. This is partially not right, shouldn't be much change at the lower rpms. I was alone on this trip but with full scuba gear (~120 lbs). I was lighter by 17 gals gas, 1 person-my son and gear (160 lbs), smaller ice chest, but same water amount aboard. So I figure maybe 175 lbs lighter in total. Not sure if that would have made that much of a difference in the speeds. Maybe the low end speeds were due to the lighter weight and the higher speeds the Permatrim/trim tab combination. I'll have to post the charts later, out of time for now, sorry.
 
Dora~Jean, keep me posted on the trim tabs because i have the same twin honda 90's on a 25 C- Dory... If they work for you then i may install them while my boat is out of the water....I pulled it two days ago for a going over....... keep your life jacket on.... tucker
 
OK, I'm ready to write my comments on using Permatrims as well as trim tabs on a CD25 with twins.

Before adding the Permatrims, I had to run my outboards all the way negative trim (to the base mount stop, no rod installed). If I tried trimming them up, even slightly, then compensating with more trim tabs, I'd lose speed at the same throttle. This convinced me that I was running the motors at an inefficient angle (prop angle) just to maximize my speed vs rpm.

I'll repeat my boat's configuration so that others might judge how their boat is similar or not, my boat is probably lighter than most. I have twin 80 4-strokes, only 2 batteries (stern mounted, both 24 size), a bait tank mounted on the splashwell (empty most trips, very light), stern anchor/chain/rode stored in aft compartment slightly forward of splashwell. I don't have a water heater, marine toilet or holding tank; boat w/trailer, full 100 gal gas, 10 gal water, full ice chest, gear for 2 people for 3 days, 6 fishing poles, radar, raft and dingy motor weighs in at just under 7,500 lbs, certified weight.

I noted yesterday that the boat felt like it had Power Steering with the Permatrims. I now believe it is because I was able to trim the motors up to a more horizontal position, thus easier turning -- vice my first idea of the down-turned edges providing better tracking. I haven't dialed in the exact angles for the combo of Permatrims to trim tabs, probably never will since it will be different every single trip -- different loads, different speeds, different sea states. But I will try to determine several baselines with say 2 people on board with gear and running at various speeds in smooth water. Then I can vary from those baselines depending on conditions.

Do I think Permatrims are worth the $150 each? Yes, for me that is. It has certainly provided the extra lift needed in the stern with my twins while reducing the angle required on my oversize trim tabs, plus the added benefit of significantly easier steering effort -- actually wonderful! I do believe it has increased my overall running efficency (fuel mileage), but won't be able to put a number on it until maybe a year's worth of trips comparing to past mileage figures. Each trip's conditions are so different.

Hope this helps others. I still need to put together my new speed vs rpm chart showing before/after Permatrims. If you do decide to buy them, I'd certainly give Andrew Munao at Shipyard Island Marina a big :thup :thup :thup . He is very knowledgeable on this product, goes out of his way to understand your needs and configuration, explains in technical detail what they will and won't do, and provides excellent tips on how to mount them. Very refreshing.

Here's his contact info for those interested:

Andrew J. Munao, Jr.
Shipyard Island Marina, Inc.
U.S. Distributor for Permatrim Marine
Toll Free #800-213-3323
Fax #920-847-2066
Website: www.permatrims.com
E-mail: andyjr@shipyardisland.com
 
If you have fuel flow guages, it would help to determine the effeciency when you run with the Permatrims. I agree about Andrew--very helpful.
I will most likely put one on the CD 25 in March.
 
William and Beth Tucker,
Yep, money, had to wait 4 months for the 'kitty' to refill, lots of "House of Mac Doh nell" fine dining...!

Dr Bob, fuel flow meters, love to have them, but still VERY low on the list. :sad
 
Here is the data with and without Permatrims. As I mentioned before, I'm skeptical that there's so much difference (11.0% average increase in speed) even at low speeds. Interesting to note the reduced delta near or just beyond hull speed. I calculated that the boat was about 175 lbs lighter on the "Permatrim" run. I'll try to get more data on future trips.

CD25_SpeedvsRPM_080227.jpg
 
Interesting--suggests that the "lift" has improved effeciency??--but hard to know until you have fuel consumption.

Was 4500 the max RPM you could achieve with the Permatrims?
 
Bob,

No, 4500 wasn't the max RPM, just the fact that I was about to see the Cabrillo launch ramp breakwater up close and personal inside San Pedro harbor! It was raining pretty hard by then too, visibility issues. I'll get a chance to wind her up on one of my trips. Beginning to eye 4-blade props now, to bring the WOT down within range where it should be.
 
Thanks for the great information. I suspect that those with overly heavy sterns and those with twins (almost twice the hydrofoil lift and lateral trim enhancement) will benefit the most from Permatrims. I can't wait to water test my boat to see if this is true. The steering improvement is something I hadn't even considered. Mike.
 
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