Honda 90 and Permatrim Observations

[tpbrady]

My wife and I just finished an excursion around Prince William Sound (Whittier - Glacier Island - Bligh Island - Cordova - Montague Island - Knight Passage - Culross Passage - Whittier) covering 319 miles in 7 days. We burned 84 gallons of gas with everything from a heavy boat at the beginning and in the middle and a light boat towards the end. We had one segment of about 20 miles that we did without any regard to fuel consumption with the rest of the time looking for best cruise fuel consumption. The speeds were from 9 to 14 mph. The one thing the Permatrim allowed me to do was run with the thrust vector of the motor more in line with the direction of travel while using the trim tabs to control fore aft and side to side trim. My real time fuel flow was reduced by using the tabs and Permatrim this way. The Permatrim also allowed me to use less trim tab to gain the right trim attitude for lowest fuel flow.

The net result is at the lower speeds best economy had the boat pretty flat on the water even at 9-10 mph. The whole trip was run with a 14 pitch stainless 3 blade prop 13.5 inches in diameter. Based on the straighter thrust vector on the motor, I believe I should be able to go to a 15 pitch prop with an improvement in fuel economy and little loss in acceleration. I can say this, the 20 mile run without regard to fuel was through 6-7 foot seas on the starboard bow. That run we did at 20-25 mph was open field running dodging the big waves, running in the troughs and then going over the crests of the smaller ones. Never once did the prop cavitate even though the motor was trimmed up. The acceleration from the 14 pitch prop was a big help in that water.

Last year on a run of 170 miles we averaged 3.5 mpg using a 17 pitch 3 blade aluminum prop. This year on the return trip of 181 miles we averaged 4 mpg. It felt pretty good to get back to Whittier after leaving Cordova with 66 gallons on board and still having 20 left.

[flrockytop]

Hi Tom,

Thanks for the detailed report. I enjoyed looking at your photo album.

Roger