Hydro Therapy

[RUNWME]

I had a friend chauffeur (thank you John MasonWATERWINGS) my wife , daughter and I around on my Cougar MTR today. I dont think John was impressed with the "training wheels" of a heavy tunnel as he prefers a Pad boat with more windshield (driving mine wind hits you in the chin) but he wore a smile as he was driving.

First time trying out a garmin legend GPS and I was trying to figure out boat efficiency.

With all of us in the boat, John ran 71.1 on GPS at 6100 rpm (tach is close when compared to digital tach in Mad EFI)
cruising along. After dropping John off, I went 81.5 at 7000 rpm. This was with a 4 blade 25 pitch through the hub ski prop and engine 2 inches lower then when set for max speed.

Both of these speed/rpm numbers equate to an approximate .08 slip. Even with me running a 4 blade through hub, I wouldnt have figured slip to be that low. Maybe my blade pitch is more then what is stamped?

A few weeks ago, with engine raised up, I turned a 26 Mazco overhub chopper 8250 RPMS. If I had a .08 slip ratio that would put me at 99.9 MPH !! Don't I wish! Tomorrow I am going to test speed with GPS and see what it is actually running with chopper prop.

I really don't want to turn this engine over 7000 RPM. Does anyone have a suggestion on what prop and size would be best for this 21 cougar MTR? I am thinking a 30 pitch chopper would be the ticket.
I have a 26 Mazco chopper or a like new 28 overhub Mazco Cleaver that I could offer in trade for a prop better suited to my combination.



One perk of adjustable ECU.
Total mileage today was 30.2 miles traveled, top speed was 81.5 and average moving speed was 59.6. It took only 9.8 gallons to top off the tanks. At 3.0 mpg, that is much better then the 1.8 I used to get before switching to programable ECU. (ofcourse this is a different engine as well)

David Bunn

[WATERWINGS]

Thanks Dave for the chance to run your Cougar today, lots of fun!

Mabey we can go out later with no wife and child so we can turn up the wick and blaze a trail with some big numbers, and try some of the props on my wall, for some MONSTER SPEED!

Thank you for the HYDRO therapy!

[RUNWME]

A little more hydro therapy for me today. I went out this morning at 9 am and conditions were very nice. 75 degrees, choppy water, no traffic and 10 mph tail wind.

I tried 5 props and lined them on JWater Wings pier and tried them one at time. Fastest prop ended up being a 28 Mazco Cleaver turning just over 8k RPM at GPS 101 MPH !

I was very happy with those numbers but it was tough to get on plane. It rode very flat and just cooked across the water.

Those are WAY too many RPMS for longevity so I will be trying bigger props to bring RPMS down.

My favorite prop was a 4 blade SKi prop. It has great punch out of the hole, and the boat handles good, but when idling at low rpms in forward gear it makes a clunking sound. None of other props I tried did this. Does anyone have an idea what could be causing it?

David