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Author Topic:   15 CENTER CONSOLE, 70-HP Yamaha

beej posted 08-05-2006 03:06 PM ET (US)
I have an [19]84 15-foot CENTER CONSOLE [with a 2006 Yamaha 70-HP two-stroke]. [What is the] optimum propeller pitch.
prj posted 08-06-2006 02:47 PM ET (US)
A 13x19 tends to be the most appropriate prop for a 70-HP engine on a 15-foot classic Whaler.
This should yield speeds in the low to middle 40's.
Peter posted 08-06-2006 06:19 PM ET (US)
42 MPH with 2003 Yamaha 70 turning a 13 x 19 Yamaha aluminum on my 15 Supersport.
Litey posted 11-06-2006 10:53 AM ET (US)
I have the 15 SS with the 2002 Yamaha 60 two-stroke. Can I just assume that an 18 pitch would better for the lesser horsepower motor?. Can I get 40-MPH? I am getting 37-MPH on an ugly looking aluminum 15 pitch right now with the motor all the way down and the cavitation plate is even with bottom.
Peter posted 11-06-2006 11:00 AM ET (US)
You don't have enough pitch. Try a 13 x 17.
Litey posted 11-07-2006 01:52 PM ET (US)
Peter you mean, I don't have enough horsepower or "too much" pitch, right? With an 18 inch. So I would be better off with a 17 pitch ? And where should the motor be raised ? another website Screamandfly.com someone said that most 15 owners run their cavitation plates about 1.5 to 2-inches above hull bottom. Do you guys agree? I did lots of searches but if you have any thread links, I would love to read more.
The Judge posted 11-10-2006 01:10 PM ET (US)
At least 2" above. I run mine about 4" with a 6" setback.
Peter posted 11-10-2006 01:43 PM ET (US)
If the lower bolts are mounted through the blind holes in the motor bracket (typical installation on a 15 classic hull), there is no opportunity to raise the motor unless you redrill lower holes or use a jack plate.
I went back and looked at the Yamaha specifications for the 60 2-stroke and see that it has a red line of 5500 instead of 6000 RPM as is the case for the 70. A 13 x 19 might be the correct propeller for the 60 on the 15 classic hull as it is for the 70 on the 15 classic. I would try a 13 x 19 aluminum Yamaha propeller. 5500 RPM with a 19P propeller should produce about 40 MPH which is what I would expect from a 60 HP motor on a 15.
Litey posted 12-01-2006 07:41 PM ET (US)
Peter , Thanks a bunch on the prop size thoughts
Which is the best bracket to use since you are correct I have the blind hole mounting . What is light weight and the best value ?
Sal DiMercurio posted 12-01-2006 08:15 PM ET (US)
Peter, why do you say the bracket holes must be re-drilled?
You don't raise the the bracket when raising the engine, you raise the engine.
I removed a 1986 - 40hp Johnson & the jack plate holes matched those mounting holes, just as the 1997 - 70 hp Johnson would match them.
There are no blind holes in my transom, all the bolts go straight through above the well & are totally accessable.
Sal
Litey posted 12-20-2006 12:30 PM ET (US)
Please reccomend a good lightweight Jackplate with minimum Setback for 15 Supersport with 60 Yam 2stroke ...
alfa posted 12-20-2006 01:02 PM ET (US)
Use the convertible MJ5 from Bob's Machine shop.
Just received mine for the 15' Sport.
You have the choice with this unit : 5" or 2 1/2" setback
Sal can tell you more
Litey posted 01-08-2007 09:06 PM ET (US)
Well Thanks ...I have been pricing them and it looks like
the Jack plate is gonna cost about 250 by the time it is shipped . My question is , how much benefit can I expect from raising up the motor . right now my cavitation plate is about even with bottom.....
Should it be raised up about 3 inches ..
Am I going to get a lot less drag , better handling etc??
Is it worth it ? I don't mind the money if it is worth it,
in some way.
Sal DiMercurio posted 01-08-2007 10:32 PM ET (US)
I've got Bob's jack plate & yes it will improve the way the boat handles & give you more speed.
Trust me, once you mount it on a jack plate & put a s/s prop on it & fine tune it, you will absolutly love it & say, wow, what a difference a plate makes.
If you get Bob's plate mount it for the 5" setback.
Sal
jimh posted 01-09-2007 01:29 AM ET (US)
You've got the perfect motor for that 15-foot classic Boston Whaler boat. The perfect propeller will really make it fly.
I recommend you read Clark Robert's comments about the speed potential of the 15-foot Boston Whaler hull. See:
http://continuouswave.com/whaler/reference/15/testimonials.html
Based on Clark's comment about the hull preferring to run with a lot of lift, it may be interesting to experiment with propellers that can provide more lift. I'll leave that to the practitioners of the Black Art of Propeller Selection.

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Author	Topic: 15 CENTER CONSOLE, 70-HP Yamaha
beej	posted 08-05-2006 03:06 PM ET (US) I have an [19]84 15-foot CENTER CONSOLE [with a 2006 Yamaha 70-HP two-stroke]. [What is the] optimum propeller pitch.
prj	posted 08-06-2006 02:47 PM ET (US) A 13x19 tends to be the most appropriate prop for a 70-HP engine on a 15-foot classic Whaler. This should yield speeds in the low to middle 40's.
Peter	posted 08-06-2006 06:19 PM ET (US) 42 MPH with 2003 Yamaha 70 turning a 13 x 19 Yamaha aluminum on my 15 Supersport.
Litey	posted 11-06-2006 10:53 AM ET (US) I have the 15 SS with the 2002 Yamaha 60 two-stroke. Can I just assume that an 18 pitch would better for the lesser horsepower motor?. Can I get 40-MPH? I am getting 37-MPH on an ugly looking aluminum 15 pitch right now with the motor all the way down and the cavitation plate is even with bottom.
Peter	posted 11-06-2006 11:00 AM ET (US) You don't have enough pitch. Try a 13 x 17.
Litey	posted 11-07-2006 01:52 PM ET (US) Peter you mean, I don't have enough horsepower or "too much" pitch, right? With an 18 inch. So I would be better off with a 17 pitch ? And where should the motor be raised ? another website Screamandfly.com someone said that most 15 owners run their cavitation plates about 1.5 to 2-inches above hull bottom. Do you guys agree? I did lots of searches but if you have any thread links, I would love to read more.
The Judge	posted 11-10-2006 01:10 PM ET (US) At least 2" above. I run mine about 4" with a 6" setback.
Peter	posted 11-10-2006 01:43 PM ET (US) If the lower bolts are mounted through the blind holes in the motor bracket (typical installation on a 15 classic hull), there is no opportunity to raise the motor unless you redrill lower holes or use a jack plate. I went back and looked at the Yamaha specifications for the 60 2-stroke and see that it has a red line of 5500 instead of 6000 RPM as is the case for the 70. A 13 x 19 might be the correct propeller for the 60 on the 15 classic hull as it is for the 70 on the 15 classic. I would try a 13 x 19 aluminum Yamaha propeller. 5500 RPM with a 19P propeller should produce about 40 MPH which is what I would expect from a 60 HP motor on a 15.
Litey	posted 12-01-2006 07:41 PM ET (US) Peter , Thanks a bunch on the prop size thoughts Which is the best bracket to use since you are correct I have the blind hole mounting . What is light weight and the best value ?
Sal DiMercurio	posted 12-01-2006 08:15 PM ET (US) Peter, why do you say the bracket holes must be re-drilled? You don't raise the the bracket when raising the engine, you raise the engine. I removed a 1986 - 40hp Johnson & the jack plate holes matched those mounting holes, just as the 1997 - 70 hp Johnson would match them. There are no blind holes in my transom, all the bolts go straight through above the well & are totally accessable. Sal
Litey	posted 12-20-2006 12:30 PM ET (US) Please reccomend a good lightweight Jackplate with minimum Setback for 15 Supersport with 60 Yam 2stroke ...
alfa	posted 12-20-2006 01:02 PM ET (US) Use the convertible MJ5 from Bob's Machine shop. Just received mine for the 15' Sport. You have the choice with this unit : 5" or 2 1/2" setback Sal can tell you more
Litey	posted 01-08-2007 09:06 PM ET (US) Well Thanks ...I have been pricing them and it looks like the Jack plate is gonna cost about 250 by the time it is shipped . My question is , how much benefit can I expect from raising up the motor . right now my cavitation plate is about even with bottom..... Should it be raised up about 3 inches .. Am I going to get a lot less drag , better handling etc?? Is it worth it ? I don't mind the money if it is worth it, in some way.
Sal DiMercurio	posted 01-08-2007 10:32 PM ET (US) I've got Bob's jack plate & yes it will improve the way the boat handles & give you more speed. Trust me, once you mount it on a jack plate & put a s/s prop on it & fine tune it, you will absolutly love it & say, wow, what a difference a plate makes. If you get Bob's plate mount it for the 5" setback. Sal
jimh	posted 01-09-2007 01:29 AM ET (US) You've got the perfect motor for that 15-foot classic Boston Whaler boat. The perfect propeller will really make it fly. I recommend you read Clark Robert's comments about the speed potential of the 15-foot Boston Whaler hull. See: http://continuouswave.com/whaler/reference/15/testimonials.html Based on Clark's comment about the hull preferring to run with a lot of lift, it may be interesting to experiment with propellers that can provide more lift. I'll leave that to the practitioners of the Black Art of Propeller Selection.