posted 06-12-2009 01:16 AM ET (US)            

I look forward to hearing how the Suzuki DF300 performs on your 25 foot Whaler.

You will probably want to use either the 16" x 18-1/2" Suzuki three blade stainless steel propeller (part # 99105-08800-185) or the 16" x 20" (part # 99105-00800-20P)

posted 06-12-2009 09:30 AM ET (US)            

I can't wait to hear your performance numbers. I have an outrage 22" whaler drive and I believe that our performance will be close. I am currently running an 1989 Evinrude 225 and am considering a Suzuki 300 for repower.

posted 06-16-2009 12:22 PM ET (US)            

If Honda is coming out with a 250, I am sure it will be a very nice 250 but I doubt it will be significantly better than anybody else's 250.

* If * it shows up a year from now, you will be buying the first year of a new model. I would not bank on anybody's speculative schedule of new product introduction in this economy. It could be longer.

On the other hand, if you wait to repower (with whatever motor) you will come to appreciate how much better the new 250 HP or 300 HP single is compared to the weight of the twin four strokes you have now.

posted 06-17-2009 10:54 PM ET (US)            

My hull is approximately 1,000-lbs lighter and four inches narrower than a 25-foot hull, but has the Whaler Drive. I've found that the 21.5-pitch seems to work fine.

I had the dealer raise the motor since I didn't see a big trim range where the trim helped. [The help from trim] seems to have improved some since raising the motor. Still not happy with the trimming, but need to spend time working with the boat to see if raising really helped. If my wife doesn't go, the grandson does, so not much time for performance testing

posted 06-18-2009 08:53 AM ET (US)            

If we figure that the OUTRAGE 22 Whaler Drive goes 50-MPH with 300-HP, we can estimate the horsepower needed to go 35-MPH from the relationship that boat speed change is generally proportional to the square-root of horsepower change.

35/50 = (HP/300)^0.5

HP = 300 x (35/50)^2

HP = 147

With 147-HP and a fuel flow of 7.8-GPH, we can figure the brake specific fuel consumption of the the motor:

BSFC = 7.8-gallons/1-hour x 6.25-lbs/1-gallon x 1/147-HP

BSFC = 0.33 lbs/HP-hour

A brake specific fuel consumption of only 0.33-lbs/HP-hour is astonishingly low for a gasoline four-cycle engine. Normally the only engines that can reach this sort of efficiency are very large marine diesel engines of many thousand horsepower, seen only in the largest of ships, or in direct-injection diesel engines such as the amazing TDI from Volkswagen. A typical value of BSFC for a gasoline engine is closer to 0.5-lbs/HP-hour.

One source notes:

"An excellent BSFC for a well-developed, naturally-aspirated, high-performance liquid-cooled engine at 100% power is in the neighborhood of 0.44 – 0.45. Claims of gasoline engine BSFC values less than 0.42 at max power tend to be suspect. At reduced power settings (in the region of 70% and below) BSFC values of 0.38 have been achieved, but they are not commonplace."

posted 06-18-2009 09:52 AM ET (US)            

WOT fuel consumption for the DF300 is about 25 GPH. Assuming it produces 300 HP, then the BSFC is

25-gallons/1-hour x 6.25-lbs/1-gallon x 1/300-HP or 0.53 lbs/HP-hour

If the boat requires 150 HP to move along at 35 MPH, then fuel consumption is estimated to be 150 x 0.53 lbs/hp-hour x 6.25 lbs/1-gallon = 12.7 GPH. This number seems to be in line with what Suzuki is reporting for boats capable of approximately 50 MPH at WOT when powered by the DF300.

posted 06-18-2009 10:57 AM ET (US)            

Based on on GTL's performance report, I am going out on a limb and recommending you start with the 16" x 20" propeller.

Though the Outrage 22 Whaler Drive is not the same as an Outrage 25, prior performance reports of the 22 WD and the 25 seem to suggest that the 25 is at least as fast, if not faster, than the 22 WD.

posted 06-18-2009 08:12 PM ET (US)            

The fuel flow is thus

1-gallon/3.7-miles x 22.1-miles/1-hour = 5.97-GPH

The 300-HP Suzuki pushed the test boat to 51.2-MPH. We compute the horsepower at 22.1-MPH

HP = 300 x (22.1/51.2)^2
HP = 55.9

BSFC = 5.97=gallon/1-hour x 6.25-lbs/1-gallon x 1/55.9-HP
BSFC = 0.66-lbs/HP-hour

Not surprisingly, the Mercury test data shows the Suzuki motor to have about double the BSFC as we have computed from the data given above by GTL. I say not surprisingly because you would expect nothing less in a manufacturer sponsored comparison. The test data for the competitor's engine would probably be cooked to show the worst possible outcome.

We have two extremes of data: a first-hand report from an owner which shows amazingly good fuel economy; a manufacturer's test report from a competitor which show amazingly bad fuel economy.

Personally I think both data points are flawed. The owner is probably too optimistic. Mercury is disingenuous and has misled us by choosing a particularly bad point for the Suzuki. I don't think the optimum fuel economy for the same boat can occur at 22-MPH for the Suzuki and then at 27-MPH for the Mercury. I suspect that Mercury has cooked the books on this one.

posted 07-07-2009 01:02 PM ET (US)            

Right now I'm considering switching the current 16" x 20" Suzuki prop to a 16" x 18-1/2". I ran the boat 3 different times @ WOT for 30 second intervals. I was by myself with 85 gallons of gas. There was a light wind and light chop.

First run: 5450 RPM and 47 MPH on GPS trimmed up

Second run, going in the same direction: 5500 RPM and 48 MPH on GPS trimmed up.

Based on everyone's replys, I think that the 16" x 18 1-2" prop will get the engine to its redline 5700-6300 RPM.