Full throttle rpms

[keith horne]

I have a question about max rpms. I have a 1986 140hp looper on a 1987 19.8f chaparral sorry but dont know the weight of the boat. But what full throttle rpms should this engine run at i have four props to dail in with one is a 13.75 x 15 omc aluminum prop boat will snap you head back when taking off runs at 6000 rpms other is same as above oem but stainless steel but needs to be reconditioned but should be about the same or a little bit better other is a hustler13.25 x 17 aluminum lost little out of hole turns about 5500 rpms speedo says about 43mph trimmed out wish i had gps maybe down the road but anyway last prop is a cabelo's 12.75 x 19 stainless steel comes out of hole like a dog runs at 5100 rpms all props seem about same speed??? would think there would be a bigger difference also bottom of boat has no paint and like new i also always wax it every spring and at end of season i am a little nuts i know but i take care of what i have work to hard for the little i have. Can anyone tell me what rpms is best and maybe which prop to use and last what maxum speed should i get thanks keith p.s gave all the info i have.

 

[kenmyfam]

Re: Full throttle rpms

I have a question about max rpms. I have a 1986 140hp looper on a 1987 19.8f chaparral sorry but dont know the weight of the boat. But what full throttle rpms should this engine run at i have four props to dail in with one is a 13.75 x 15 omc aluminum prop boat will snap you head back when taking off runs at 6000 rpms other is same as above oem but stainless steel but needs to be reconditioned but should be about the same or a little bit better other is a hustler13.25 x 17 aluminum lost little out of hole turns about 5500 rpms speedo says about 43mph trimmed out wish i had gps maybe down the road but anyway last prop is a cabelo's 12.75 x 19 stainless steel comes out of hole like a dog runs at 5100 rpms all props seem about same speed??? would think there would be a bigger difference also bottom of boat has no paint and like new i also always wax it every spring and at end of season i am a little nuts i know but i take care of what i have work to hard for the little i have. Can anyone tell me what rpms is best and maybe which prop to use and last what maxum speed should i get thanks keith p.s gave all the info i have.

There are a lot of more experienced people out here than I am and you should listen to them before me. However, here is my take on this. I run the same motor (although a 1985 model) on my Doral 164 (16' 4 ")
I have tried 2 different props on my motor. Set up is good both height wise and angle of full down trim. 14" X 17" aluminum prop (uncupped) gives me 46mph with GPS at 6,200 rpm. Hole shot is instantaneous.
14" X 19" aluminum (cupped) gives me 46mph at 5,400 rpm. Hole shot marginally slower but still picks up a 200 lb skier with no problems. It does not seem to matter how many on board with either prop, the performance remains the same. I think the experts out here will tell you 6,000 rpm is good and below 5,500 rpm at WOT is borderline "lugging"
Personally, I am going to try a 14" X 17" (cupped) in the spring and see what happens. Maybe my hull design and horsepower makes what I have now my max ?
Please wait for the experts responses as I am a rookie with props and good luck.