Question about Evinrude V4 120

[CSANDIFER]

I recently purchased a 1993 Hydrosport 185 CC equipped with a Evinrude V4 120 ocean pro (1993). According to the Hydrosport book the boat weighs around 1750lb. I have a steletto stainless steel(cupped) 17 1/4(i think) by 15 prop. Full throttle gives me around 5800 rpms with a speed of 28.7 mph. I was wondering how to get more out of the engine. The engine did have a 19 pitch on the boat and it would give 35-37 but at 6500 rpm. The motor manual states not to exceed 6000 rpm. I usually run the boat full of gas (80 gal) with only two people in it. Engine runs great. Compression gives about 120 - 130 on all four. Any ideas are appreciated. Anybody know the reputation of these motors?

 

[DJ]

Re: Question about Evinrude V4 120

HYDROSPORT,<br /><br />You do not want to turn 6500 rpm's. Your rpm/prop comparisons do not compute. The 19" should give you less rpm than a 17".<br />As Rule of Thumb, figure 2-300 rpm per inch in prop. I wouldn't twist the engine much past 5800.

 

[DJ]

Re: Question about Evinrude V4 120

Hydrosport,<br /><br />Forgot something. The steel cupped prop has a more efficient bite. It will hold rpm's down. Stick with the one that runs around 5800 @ WOT.

 

[SeaDawg]

Re: Question about Evinrude V4 120

Something does not look right though. I don't understand why you are getting that much more speed and also the high RPMs with the 2nd prop. <br /><br />I would expect a 17 pitch cupped to perform fairly similar (speed and also RPM) to a non-cupped 19 pitch prop, all other things being equal.

 

[Dhadley]

Re: Question about Evinrude V4 120

I think what you have is a 13 1/4 x 15. Stilettos have a lot of bite and you can run them faily high. Try raising your motor to increase the X dimension. That should give you more RPM's and allow you to go to a larger pitch prop. Stick with the Stiletto -- they are hard to beat. <br /><br />You are correct about the RPM's. 5800 with a max load is where you want to be. The rev limiter is either at 6200 or 6700 depending on which pack you have. <br /><br />Raise the motor (watch the water pressure closely) and let us know.<br /><br />Good luck!