governor effect

[Casey]

ALX 357

The storm blew over, I pulled the GWK out of the water for the potential hurricane. On my last trip out to Ship Island, my trim tab fin fell off and chewed into my propellor.

The cavitation plate is 1.5 inches below the hull.

My boat was originally bought in Colorado and propped with a 11.25 inch diameter with 10 pitch standard 3 bladed aluminum prop.


Hope this helps. You should be getting more speed under WOT.

[ALX357]

Casey, would it be possible for you to send out a photo or post it here ? showing the mounted height of your motor, vis. the top edge of the transom and the bottom side of the motor mount's hanger over the transom. Mine is mounted as low as it could have gone, and i am planning to raise it maybe two holes up, without having to re-drill any new holes in the boat. ... just curious, and will post a picture next chance i get for comparison.
I "borrow-bought" a discounted new Mercury 11.25 x 10 prop and will try it next weekend. (75 dollars, and refundable if I don't want to keep it )
The 11.25 x 10 really looks radically different than the 12.25 x 9 pitch prop that has been the best so far.... ( 16 ~ 17 MPH at 4400 RPM - WOT) not just a bit less diameter and a bit more pitch, but a totally different blade shape

[Casey]

I moved the boat to Oklahoma during the last hurricane and am getting the house ready to rent out. What a bummer. Lots of intermittent good weather now. I will be happy to take a picture of my set up and post it when I get back to Oklahoma. I can't wait till I get it back in the water in a lake and sail again. It will be about two weeks.

I have not tried a different blade shape so I am unfamiliar with other types. The Anchorage had done several tests and I was happy with what they had accomplished.

[ALX357]

NOT YET having raised the motor up, i tried the 11.25 X 10 prop last weekend. With it the boat went 15~16 mph, at 4200 RPM WOT. That is about one mile per hour less and 200 RPM less than with the 12.25 X 9 prop. Need to get that motor raised up a couple of holes before any final propeller decisions can be made....

[ALX357]

.....motor raised up by two holes, ventilation / cavitation plate level with bottom edge of transom / hull. Using 12.25" x 9-pitch Black Max Mercury prop, now getting 17 MPH with me alone, and a few hundred pounds of load. Engine turning 4500 RPM, tach gauge checked, wired correctly, not sure if it is "calibrated" accurately, but the engine runs smooth, holds full throttle for half-hour or more without overheating, missing or mis-behaving - so i am finally at a point where i am satisfied with the performance, even if i never figure out where the other 1000 RPM, more or less, are to be found.

[Dan B]

I have a similar problem with my Yamaha F50. Only reaches 4200 rpm at WOT. Top speed with 5 people, gear, ... is around 10 knots. I am less worried about top speed, more about not achieving 5500+ rpm at WOT.

I have already -
1) Installed lowest pitch prop for this motor
2) Checked all fuel lines
3) Replaced fuel assembly
4) Adjusted choke
5) Adjusted throttle linkage
6) Added some carb cleaner
7) Had compression checked
Cleaned fuel filter
(interesting - typing the number 8 and a ) gets you a smiley)

Only things I can think of yet to do are -
a) Have carbs checked (cleaned and synchronized)
b) Have fuel pump checked

I have asked on many boards and called mechanics. The first (and usually only) response is "check the prop" - except of course on this board which is by far the most helpful one I have seen.