F150 Cruise RPMs

[dmorrison]

I have a F150 turning a 13.75 X 19 SS Yamaha Reliance prop. At WOT i get 5300 (Edgewater 188cc 1/2 fuel and one other person). I was wondering if cruising at 4600 rpm for an extended time (2-3 hours) would hurt the engine? What is the recommend max cruise for these engines?

[boats.net]

No that wont hurt it, you can full throttle if you want to. That engine can turn 6000 rpm's, it could use a 17 pitch prop.

[dmorrison]

I don't really want to reprop so I have another question. Does an overpropped engine only suffer when ran at WOT or does it hurt it over the entire range of rpms?

[horsetrader]

RE: F 150 cruise rpms

dmorrison,

yes, you are lugging that motor throughout the rpm range. Short term, it will be fine. However, if left as is, the life span of the motor will be reduced. When propped correctly, WOT should be as close as possible to 6000 rpms. I also have an F 150 on my Outrage 18. After much experimentation, I have found a great prop for my application. I'm using the Stiletto 14.25 x 17 Advantage II prop. At WOT, I get 5800 rpm @ 47 mph. It sounds like your setup would do well with a 17" P as well. Hope this helps.

[dmorrison]

Thanks for the useful advice. I will reprop with your recommendation.

A reputable prop shop will let you try props and return the ones that don't work (no dings)! Good luck
Jim

[dmorrison]

Ron,

What is the approximate total weight of your boat when you are getting 5800 at WOT? Under my test conditions I was approx. 3000 pounds.

[horsetrader]

dmorrison, I'm guessing that with the motor, ~30 gallons of fuel, 2 batteries and other misc gear, the total weight is about 2500-2700lbs. And if I had full fuel tank, the total weight is closer to 3000lbs. I am able to get 5800 rpms consistently pretty much regardless of weight. Of course, this is with the motor trimmed out. Look on the Yamaha website for F 150 performance review. I think they used a boat very similar to yours for the test. The perfomance numbers you see in the review are very close to what I get with my boat/ motor/ prop combination. hope this helps.