Finally, our first Alaskan family cruise

B

breausaw

New member
The first time we took our boat out it had ¾ tanks of fuel with no gear or water on board, top speed was around 32mph.
This last weekend was our first real trip out of Whittier Alaska into Prince William Sound, we had full Fuel, Water, Permatrim installed, food and gear, our top speed @ wot was about 27 mph.
We cruised around a lot at 4500 RPM and achieved about 20 mph, final fuel economy was about 3.6 mpg; a little disappointing.
GO FASTER DAD, GO FASTER DAD!
So what RPM and speed should I expect for optimal fuel economy?
At 4000 rpm my best GPS speed was around 16.5 to 17mph.
Best speed was always achieved with motor in extreme down position, bumped up a little off the stops to reduce engine noise.

We did however have a wonderful time and were able check out all systems, which worked wonderfully. Our tender had not arrived yet so we used the Anchor Buddy stretchy line when we went to the beach, it worked great! Have it attached to spare anchor in the port laz, just drop about 30 feet from shore, beach the boat attach a line and push the bow back out. Of course we took tide and surf conditions into account and picked a fairly steep sandy beach.
Stayed two nights, traveling about 110 miles, saw a lot of wildlife, and got skunked on the fishing.
I’ll post some pictures when I have a chance, crazy week coming up.
 
Jay,

The speed for best economy is pretty variable based on load and weight distribution and prop. What is your current powerplant and what prop are you using on it? Since you top speed dropped about 5 mph if sounds like you were pretty heavy.

Tom
 
tpbrady":2bqtp57i said:
Jay,

The speed for best economy is pretty variable based on load and weight distribution and prop. What is your current powerplant and what prop are you using on it? Since you top speed dropped about 5 mph if sounds like you were pretty heavy.

Tom
Click to expand...

3x13 1/2x15 on 06 honda 90.
Have a 13 1/2 X 15 COMPOSITE 4 blade as backup, my try it out.
Just need to take my time and enjoy the ride.
 
Personally, I think you did great, mileage wise. And your family also enjoyed the boat. I don't think you're going to do much better with a full boat, at 18 knts. These light boats lose mileage when loaded. With a C-25, I'd be ecstatic with that mileage at those speeds.

Boris
 
Jay: you could be a bit under-propped. Your speed/RPM combinations are very similar to my own (different engine setup) and I always like to run lower pitch props due to the weight we carry and for better control in rougher water at low speeds. It might also be load weight that caused your drop in performance, especially if the boat felt noticeably "lighter" during the initial run. The prop issue is resolved as follows: at WOT with a normal load (whatever that is) your RPM should be within the engines WOT RPM range. Where you are in the range would give a relative sense of how you're propped. If you will always run heavy your prop is likely fine, and a softer ride will compensate you for the drop in fuel economy. Best, Mike.
 
Jay,

I dropped to a 3x14 pitch 13.25 diameter stainless prop on my BF90D. Given the year model of your boat I assume you have the same engine. When you are operating at 4500 rpm you are running at a good rpm but not the most efficient for the engine when the boat is loaded. I saw comparable mileage with the 15 pitch prop at 4500-5000 rpm in calm water, but when I slowed down due to rough water the mileage dropped a fair amount when operating at about 4100, at about 14 mph. With the 14 pitch prop, I still had nearly 32 mph light at WOT but heavy I got 30 mph and at 4100 rpm and 14 mph, I averaged 4.4 mpg over 72 miles two weeks ago. However, if I pushed it up to 20 mph mileage dropped to around 3 mpg. It slowly creeped up as I sped up to 26 mph where it came in at 3.4 mpg.

The 14 pitch is quite responsive so it's the prop of choice now.
 
journey on":3aaq7k6n said:
Personally, I think you did great, mileage wise. And your family also enjoyed the boat. I don't think you're going to do much better with a full boat, at 18 knts. These light boats lose mileage when loaded. With a C-25, I'd be ecstatic with that mileage at those speeds.

Boris
Click to expand...
I don’t feel so bad now, but thought I’d get much better fuel economy. Met a guy today with 00 CD 22 while waiting at Whittier tunnel who ran his boat at 4700 RPM with twin 40s and said he gets about 4.5 mpg.
At some point I have to wonder if folks are exaggerating a little.
 
This MPG thing is really variable laden! I don't pretend to be a prop wizard nor am I into the gimmicky items that will give my exact fuel burn at any point in time. I do however have some rudimentary math skills and employ them once a year to form my opinion. Our 25ftr holds 100 gallons. When it's low I fill it up paying attention to the previous hour meter reading and the gallons consumed. Depending on how much trolling was done with the 150 Honda or how many 200 mile trips were taken I can still come to an agreeable place by averaging. Depending on the above we burn between 2.5 and 3.5 GPH season after season.

We were out of Whittier last week as well and it was really nice.
Mike
 
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