prop size

[beeboater]

I have an wellcraft 190cc with 150 Johnson Ocean runner counter rotate the prop on the engine is 14.5 X 19 when staring on bow seems to come up too much until i get on plane, but top end seems too fast at 4800 rpms i have to run at 3,000 rpm . what should i do to bring more power to get on plane and rpms higher at cruising speedhttp://forums.iboats.com/images/smilies/confused.gif

 

[steelespike]

Re: prop size

You don't say what year motor but I believe the 150 is rated at 5,000 rpm
typical motors most look for max rpm about 5,500. So your actually a little low for max rpm.Bow will tend to rise on hole shot.Are you trimming in all the way?Are batteries/gas at or near the stern?Do you have any ventilation/cavitation issues?Is the antivent plate(just above the prop) about even with the bottom of the boat?What did you mean you have to run at 3,000?

 

[Dhadley]

Re: prop size

Typically when folks refer to an 150 Oceanrunner they are refering to a 60* motor. Those can be safely propped out at 5800-6000.

 

[Tail_Gunner]

Re: prop size

I have an wellcraft 190cc with 150 Johnson Ocean runner counter rotate the prop on the engine is 14.5 X 19 when staring on bow seems to come up too much until i get on plane, but top end seems too fast at 4800 rpms i have to run at 3,000 rpm . what should i do to bring more power to get on plane and rpms higher at cruising speedhttp://forums.iboats.com/images/smilies/confused.gif

Sounds like you have a little bit of setup work to do...Your a 1000 under rpm now..and you dont like the speed.. Id suspect when these guys are done you wont believe how much boat you have..

 

[beeboater]

Re: prop size

engine year 1998, when i say 3,000 rpm is where it is comfortable. the trim is in and all batteries (2) are in the rear. all i want is to get up on plane quicker and speed top end speed isn't a concern.

 

[hwsiii]

Re: prop size

It sounds like you have a prop with a decent amount of rake in it, which is lifting your bow high. I don't know what the real RPM or lower gear ratio is, but what I found in my database says it should turn 4,500 to 5,500 RPM and it shows the gear ratio as 1.86 to 1 with the boat weighing in at 2,350 pounds empty. if it is a 1998 too. If i use these numbers asd a starting point, and add the motor, 40 gallons of fuel, a couple of people and sundry items I come up with a total weight of about 3,700 pounds. If I also use this weight I find that if you change to a 17" prop in the same model of prop you have now, your RPM will rise to about 5,200 to 5,300 RPM with a speed of about 40 some miles per hour. But if you change models of prop to something with less rake it is hard to tell, because I don't know what other geometry of the prop changed as well. Using the 17" prop you will get on plane much quicker.

H

 

[Dhadley]

Re: prop size

If your top rpm is only 4800 the holeshot will indeed be horrible I would think. Once you get the set up sorted out and get the rpm up close to 6000 the holeshot should improve greatly.

 

[hwsiii]

Re: prop size

Beeboater, if you stay with the same model prop I ran my formulas and this is what you can expect if you stay with the same model prop but change to a 14 1/4" x 17" prop. When you change to different models of propellers in nstainless steel, the basic elements in the geometry of the prop change and I can't say for sure what you should expect. That is just the difference in propellers, some have high rake which lifts the bow, while others have a zero rake which lifts the stern. Also some props have cup and others don't as well as some are progressive pitch and some aren't. That is why I can't be definitive when you change models of props.

I hope this helps you, stainless propellers have many features that most people don't understand what those features do for a boat, that is why it is so hard to pick the right propeller. your RPM should be right at 5,500.

H