25 cruiser fuel consumption?

Jack,

I rather doubt that a permatrim will improve your fuel economy on average and will likely slightly decrease it overall. The primary advantage of permatrims is that you will get up on plane at a slightly lower speed and you have a way of adjusting "pitch" that is independent of (and probably more fuel efficient) than trim tabs (which can then be reserved for adjusting "roll"). Hence, the speeds at where you might gain fuel economy with the permatrim are the speeds between where you get on plane now and where you will get on plane with the permatrims (probably a 3kt range around 12-15kts).

At higher speeds the permatrim will add a little drag and likely will decrease fuel mileage (albeit slightly). You'll also probably lose a kt or two on top end speed (at least that's my experience on my previous 22). What I gained from the permatrims was an ability to push the bow down in chop and improve the ride at higher speeds. To me this was a good trade off especially on a boat with twin engines and no trim tabs.
 
Roger,
Thanks for the informative reply. I think I will save my $$$$ from not buying a PT and put it in a Lewmar Capstan for pulling my anchor.
When out fishing with friends I "let them" retreive the anchor after pulling it with the sliding buoy & ring. But when just me and the 1st mate are out it is me pulling that 600' of 1/2" line in. A capstan would be very useful.

Jack on the HIGH TIDE II
 
I've had Permatrims on two boats, a 22 and a 25. The best use of a Permatrim is to correct a fore/aft trim problem that can't be fixed otherwise. The 22 is generally well balanced fore and aft and is mainly affected by how you load it. The Permatrim didn't really offer much other than lowering the planing speed about 1.5 mph. The 25 is just plain stern heavy. The Permatrim does what the Lenco's can't do and that is get the bow down where it needs to be most of the time. Even with the Permatrim, I use a lot of trim tab at low speeds to get the best fuel economy. I know it sounds counterintuitive, but the fuel flow meter doesn't lie very often.

On the TomCat, it seems the Permatrims really help get the bow down at lower speeds and more importantly help port/starboard leveling. I can't speak for experience there.
 
Agree that the Permatrim will not increase the fuel mileage, but will put the bow down more on the 25 and the boat will do better with chop. I tried with and without Permatrim. The 130 is marginal for the 25--and the Permatrim, did improve planing speed. The ride was much better.

The Tom Cat, only allows a lower planing speed--does not do much for the ride--and probably decreases the top end speed slightly. I don't think it really changed the mileage. (I would call it more stern lift, than bow depression--you don't want bow depression on a cat).

I have never had a port to stb probelm with leveling--so have not used the Permatrims on the Tom Cat for that. Mine right right on top of the water on the 255.
 
Anyway you look at it these boats go farther on less fuel than most other boats out there. I just returned from a lengthly trip down the grenville channel from prince Rupert playing around in areas in which the only other boats seen were tugboats, ferries or 50 Plus foot yachts. In these days of outrageous fuel prices you can't go wrong with a c dory.
 
with fuel at $4/gal in the US and God knows what in Canada, here are my comments.

1. Weight is the most important factor in fuel mileage. As mentioned above, us cruisers add a lot of weight to the boats.

2. Speed is a driver. We cruise a lot at hull speeds, and the mileage increase is wonderful. When my 3100 worked, I'd see 6-8 mpg.

3. I've re-pitched the prop to 16". this doesn't increase the speed but it does help the mileage.

4. After fuel changed to part ethanol, the mileage dropped by 1/2 mpg. Drove me nuts to figure that out.

5. If you have trim tabs, use them to get up on plane, but if you want to go >20 knts, pull them up. Doing this gets us up to ~25 knts, but boy, does the ride get rough.

6. I'm not sure what I said above, but there is no fuel tank return line on a Honda fuel-injected motor. So there is no problem on installing a fuel flow meter. An automobile engine has a tank return line.

Boris
 
Aurelia,
Generally you can go with the same size/pitch prop in SS as in Aluminum. However, there are many other factors in the prop beside the diameter and pitch, which include cup, rake, number of blades etc.

Some of the dealers on C Brats will have a lot of experience with what prop is best for the boat. The group who I have depended on is "propgods" www.propgods.com. E-mail them the current engines, boat, with weight, WOT speed, and RPM at WOT, and model number of the current props (if not available, at last the diameter and pitch). They will have a very good suggestion, which takes into account all of the factors.

Here is a set of two articles on the Boston Whaler site which are good references on props:
http://continuouswave.com/whaler/reference/prop1.html (ss is addressed in part 2).

Another good article on props is at: http://www.boatfix.com/how/props.html
 
I now have 689 miles on my new prop combination and have used 235 gallons of gas. That is slightly more than 2.9 statute miles per gallon. The last trip was mainly run at 22-26 mph over 188 miles using 64 gallons. The water was mainly flat and I ran with the autopilot. About 18 miles was at hull speed.
 
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