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Repowering Super Sport 15
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| Simon |
Posted on 11/27/15 - 9:16 PM
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That's an awesome bday present to yourself. Happy belated.
I thought the break in procedure/process will take much longer, so good to know I can probably break it in in one day. I can't wait until my test run. I've never even driven the boat before.
Glad to hear everything worked out great for you!
Simon
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| tedious |
Posted on 11/28/15 - 7:30 AM
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Simon, I don't remember the exact break-in process other than the 1 hour puttering around part, but I do remember that dealer/mechanic I bought it from was adamant that Yamaha four-strokes are better off when run hard during the break-in. I have subsequently seen mention of problems with rings not seating when the motors were babied. So follow the manual, for sure, but once you get past the required slow speed running, let 'er rip!
Tim
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| TookyAndNatasha19 |
Posted on 11/29/15 - 10:37 AM
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Tim, Simon and Sailorman,
What kind of top speed do you get with the Yamaha F70, and a lightly loaded Sport 15?
Paul
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| tedious |
Posted on 11/30/15 - 5:47 AM
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Paul, I am intentionally a bit underpropped, as I am in the ocean and almost never get a chance to run fast and light. I therefore run out of RPMs before I run out of power and trim - I hit between 41 and 42 MPH at 6400 RPM, with 25% trim. The great thing with my current prop (Power Tech SCD3, size 13 x 16) is that I can hit 40 with little to no trim, which is important when things are bouncy and you're looking to keep the 15 from going into orbit.
Some day I'd like to try a higher pitched prop, just to see what it could do, but in day to day use this one is fine.
Tim
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| sailorman |
Posted on 11/30/15 - 7:46 AM
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I'm still learning my new motor. With that said, I can reach 40MPH at 6300 with 50% trim lightly loaded.(My boat has bottom paint) I am pretty sure I will refine those numbers when I get more comfortable going that fast. Just to clarify, I ended up getting a Yahama 13.25 X 15 aluminum prop. Thought I was getting a 16 but turns out I got a 15. I am pretty surprised that at 5800 when you put the throttle down you can really feel additional acceleration from there up ti 6200 - 6300. It looks like I may be able to squeeze out a bit more maybe in speed/RPMs by working with the trim. Top end speed is not really my priority but it is fun when the water is flat.
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| tedious |
Posted on 11/30/15 - 3:01 PM
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Just to clarify, in case someone is wondering, the redline on the F70 is 6300 RPM and the rev limiter starts to kick in at 6450.
Tim
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| TookyAndNatasha19 |
Posted on 12/01/15 - 12:05 PM
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Tim and Ron,
Those are indeed fast speeds at top end. Ron, I agree with you about top speed not being an important variable in prop selection or motor selection for that matter because a sport 15 can only maintain high top speed when the water is like glass. This, of course, is an exceedingly small percentage of time when these boats are used.
Thanks for responding guys.
Paul
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| EJO |
Posted on 12/01/15 - 12:53 PM
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Do you guys with the F70 need that HP or the RPM to get to that low 40ies speed with those props.
I with my Montauk 150 can get only get to 34-35 at 6000 rpm with my 60HP. So I'm wondering if I get a pith higher than 14 will she go faster?
Skipper E-J
m/v "Clumsy Cleat" a 2008 Montauk 150 |
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| Phil T |
Posted on 12/01/15 - 1:02 PM
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EJO -
The 15' Super Sport has a dry weight of ~580 lbs.
The Montauk 150 has a dry weight of ~950 lbs.
The higher speed of the 15' super sport is due to being 370 lbs lighter and 10 more horsepower than the Montauk 150.
The performance report of the Montauk 150 lists the exact performance you are obtaining, 35 mph @ 6000 rpm as shown in their report:
http://www.bostonwhaler.com/boat_grap...4003PM.pdf
In your case increasing pitch will reduce your WOT rpm's and will most likely result in less speed.
If you are unhappy with the WOT performance, your choice is limited to increasing your horsepower.
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| tedious |
Posted on 12/02/15 - 4:58 AM
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E-J, I have seen many reports of 15s with F60s meeting or exceeding the 41-42 MPH that I can hit. And I am sure that if top speed was a priority, I could go faster. So the answer is "no" on whether 70 horses is really needed.
Your boat and situation is completely different. Unfortunately, the mandatory motor tie-in has resulted in you being a bit underpowered.
If you are currently running an aluminum prop you might be able to squeeze out a little more speed by changing to a quality, stainless one, but the improvement would likely be minimal.
Edited by tedious on 12/02/15 - 9:16 AM |
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| EJO |
Posted on 12/02/15 - 9:16 AM
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Phil that is what I thought (lots of weight difference) and as tedious said B-4, I too can very seldom run flat out as the water is never that smooth and I'm happy with my top speed I just want a better hole-shot although at 35mph(6000 rpm) my 3-bladed Vengiance (13-5/8 x 14) is hardly slipping.
We'll try some 4-bladed props next spring when the water is thawed. With 200 hrs on the Merc I can never convince the Admiral to change to an F70 although I would like to try that set up on a 150, maybe 10 years from now when it is time to re-power.
Skipper E-J
m/v "Clumsy Cleat" a 2008 Montauk 150 |
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| tedious |
Posted on 12/03/15 - 5:12 AM
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E-J, you never know until you try, but I'd guess a 4-blade prop might well reduce your hole shot - you want a little slip on the bottom end of the power curve to let the motor spin up. As I have said in other threads, I had good luck going to a prop with less blade area and low rake - it greatly improved acceleration and I did not lose anything at the top end.
I am not familiar with the Vengeance prop,so I can't compare it to what I ended up with - Power Tech SCD3. However, I had a great experience contacting Power Tech and getting a recommendation from them. Once I explained my situation in detail, they came up with what seems to be an excellent choice.
Tim
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| EJO |
Posted on 12/04/15 - 8:15 AM
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Tim I agree the Power Tech service is great and they gave me some recommendations including not to change, but from a fluid dynamics/mechanical standpoint based on RPM's, blade area, possible slip, and power. Theory will tell me one thing and only trial will tell.
A 15 foot Glastrom speed boat reacts different than a 15 foot Boston Whaler CC with the same power source. To the prop manufacturer they are both 15 hull of a certain weight with exact same motor resulting in the same prop recommendation.
Like I said before I'll know this coming spring.
Skipper E-J
m/v "Clumsy Cleat" a 2008 Montauk 150 |
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