Prop Recommendations

[Landon116]

I have an '01 Johnson 70 HP on a 17' Fiberglass CC (Hydra Sports) maybe 1800-2000 lbs wet fully loaded that at WOT hits ~5000 RPM with its current prop at about 29 MPH. The current prop is a Power Tech 4 Blade SS 14" Dia. x 15 pitch. This prop is very heavy! After doing some research, this prop is intended for V-4 engines stated by the manufacturer. I think this is where my RPM's are going as the engine is low hours and I have fine-tuned every adjustment, it runs very good. I am looking for top speed as we rarely do any water-sports, just running the river for long distances and running the ocean to the reefs. The only need for hole-shot in my case is getting moving in the inlet when the tide is ripping, but not a big concern. Im thinking an aluminum 3 blade 13.2 x 19p for the first shot at it. Recommendations?

 

[Sea Rider]

What's the min-max wot rpm range for said motor ? if not mistaken should be -5-6K ? if so, the motor is revving at the min lugging side of its rpm range which is real bad. How about going for same SS 4 blade prop with 13 pitch, will bump wot revs higher than now. Personally like to play with less less prop pitches from current prop. The only way to know how well will a 3 blade 19 pitch will work will be buying it, making a wot water test as loaded and check the max wot rpm achieved...

Happy Boating

 

[Landon116]

What's the min-max wot rpm range for said motor ? if not mistaken should be -5-6K ? if so, the motor is revving at the min lugging side of its rpm range which is real bad. How about going for same SS 4 blade prop with 13 pitch, will bump wot revs higher than now. Personally like to play with less less prop pitches from current prop. The only way to know how well will a 3 blade 19 pitch will work will be buying it, making a wot water test as loaded and check the max wot rpm achieved...

Happy Boating

4500-5500 is the min-max WOT range found online, 5,000-6,000 is stated in my factory service manual. Thanks for the suggestion, Ill look for one.

 

[racerone]

If you are hitting 5000 RPM with your 15" prop you certainly DO NOT want to go to a 19" prop !!!

 

[jimmbo]

01, that would be a 4 stroke?
Does the current prop have Vent Holes?

 

[Landon116]

If you are hitting 5000 RPM with your 15" prop you certainly DO NOT want to go to a 19" prop !!!

Yeah thats true, I was just figuring with reducing to a 3 blade aluminum I would be losing probably 7 or 8 pounds and I still want more top speed. But I agree, 19" would probably be overkill and the opposite of what you would do to increase WOT RPM.

 

[Landon116]

01, that would be a 4 stroke?
Does the current prop have Vent Holes?

Its a 2-stroke 2001 Johnson J70PLSIS. An no, the current prop does not have vent holes.

Thanks-

 

[Tim Frank]

You might get better focus and different opinions in the Prop Room.....it is just down the hall.

edit ~ you won't get bad info in here, but it is a more specialised room so you may get more eyes with more info.

 

[racerone]

2002 model was a 4 stroke.

 

[flyingscott]

You need to be closer to 6000 rpm with a light load.

 

[Sea Rider]

4500-5500 is the min-max WOT range found online, 5,000-6,000 is stated in my factory service manual. Thanks for the suggestion, Ill look for one.

Better work with the wot rpm stated in the Service manual, those guys never post wrong tech data. With new prop motor should rev middle to max wot rpm range. For the record, post max wot revs achieved as loaded.

Happy Boating