SPORT 15 with F70

Optimizing the performance of Boston Whaler boats
El Rollo
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SPORT 15 with F70

Postby El Rollo » Wed Apr 03, 2019 12:32 am

I have a 1988 Boston Whaler 15 with a Yamaha F70 and a five-inch manual jack plate.

I have added additional weight to the boat: a trolling motor and three small batteries.

When I finished the project of restoring the boat, I tested several propellers. Ultimately I found that a four blade worked best overall for this' particular set-up. With the odd weigh-distribution of the boat, the four-blade helped keep the bow down, and reduced bow oscillation. I saw much better [acceleration from a standing start] as well as a reduced and more comfortable cruising speeds. Docking and off-plane maneuverability was also greatly improved with the four-blade. One unexpected characteristic of the four-blade was the ability to raise the motor higher than with the three-blade. I am very happy with the current set-up.

TFrere
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Location: Lafayette, LA

SPORT 15 with F70

Postby TFrere » Wed Apr 03, 2019 9:31 am

EL ROLLO: what propeller did you choose for your SPORT 15? I have the same boat (1985 15’ Sport) and engine (Yamaha F70) but without the jack plate, the trolling motor, and the extra batteries. I have been considering a four-blade. Most of my running is in the 4000 to 4500-RPM range and top-end speed is not important.
1985 15’ Sport with Yamaha F70

El Rollo
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Re: SPORT 15 with F70

Postby El Rollo » Thu Apr 04, 2019 11:58 am

TFrere: the propeller I have is a Turbo Flats X 13-1/4" x 14" and is now named the Turbo FX4. Yamaha bought Turbo propellers and re-branded some of the names, but kept the same propeller design for this model.

Keep in mind that I selected this propeller as a bandaid to help compensate for the additional weight, and poor weight distribution in my 15.
The jack plate allowed me to raise up the engine higher than I could have if it were mounted on the transom.

I have a feeling you wouldn't be satisfied with my particular prop in your case.

Someone on this board did some good research and was happy with a Powertech SCD propeller. I believe the SCD stands for Semi-Cleaver Design. There are three- and four-blade versions of this propeller available.

I seem to remember someone on this forum said the Powertech propeller worked very well with the F70 on his 15 and he was extremely happy. I plan on trying the Powertech some day, just for kicks.

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Phil T
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Re: SPORT 15 with F70

Postby Phil T » Thu Apr 04, 2019 2:13 pm

TFRERE: I think El Rollo is referring to a 13 x 16 PowerTech SCD; that is the propeller I have on my propeller recommendation sheet from members testing.

If you want to know the four-bladed size conversion, I would consult Ken at http://www.PropGods.com. He knows Powertech and Boston Whalers. He has help a lot of owners here and he can get you the right propeller on the first go.

Sound right, El Rollo?
Member since 2003
1992 Outrage 17, 1992 Evinrude 115

TFrere
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Location: Lafayette, LA

Re: Thanks

Postby TFrere » Thu Apr 04, 2019 3:27 pm

Thanks Phil
1985 15’ Sport with Yamaha F70

El Rollo
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Re: SPORT 15 with F70

Postby El Rollo » Sat Apr 06, 2019 5:58 pm

Phil T wrote:TFRERE: I think El Rollo is referring to a 13 x 16 PowerTech SCD


PHIL--Yes and thank you. [A 13 x 16 PowerTech SCD propeller] is indeed what I was referring to. I"m very curious as to the characteristics of the Powertech SCD four-blade propeller compared my current propeller.

In calm water the tips of my current propeller are actually breaking the surface of the water with the motor trimmed out about halfway. In tight turns, the propeller still does not [ventilate], which is great. Thank you for your great feedback.

TFrere
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Location: Lafayette, LA

Re: SPORT 15 with F70

Postby TFrere » Sat Apr 06, 2019 6:19 pm

Phil: I contacted Ken with Propgods and he recommended the PowerTech SCD4 in 16-pitch. Thank you [and thank you EL ROLLO]
1985 15’ Sport with Yamaha F70

El Rollo
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Re: SPORT 15 with F70

Postby El Rollo » Sun Apr 14, 2019 7:01 pm

TFrere wrote:Phil: I contacted Ken with Propgods and he recommended the PowerTech SCD4 in 16-pitch. Thank you [and thank you EL ROLLO]


If you can, please report back with your thoughts and results of the new Powertech prop.
I am really curious how it works out for you.

TFrere
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Re: SPORT 15 with F70

Postby TFrere » Sun Jun 09, 2019 10:32 pm

El Rollo: I ended up purchasing a SCD3 in 17-pitch, but haven’t been able to test it yet. My wife and I took a ride but she gets nervous when the boat gets over about 35-MPH
.
My engine is mounted at two-holes-up. I think I need to raise the engine one more hole.

I’ll post again after further testing.
1985 15’ Sport with Yamaha F70

Simon
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Re: SPORT 15 with F70

Postby Simon » Sun Jul 07, 2019 5:44 pm

I plan to soon replace my aluminum propeller, and I have been researching the POWERTECH SCD3 propeller.

What are [the results] with the 16-pitch?

With the 17-pitch?

I'm still deciding which pitch to purchase. I have an F70 on a 15 CENTER CONSOLE. Thanks.
1987 15' Sport CC

TFrere
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Re: SPORT 15 with F70

Postby TFrere » Sun Jul 07, 2019 10:55 pm

I’m turning 6000 RPMs with the SCD3 13.25 x 17. My boat is a 1985 15 Sport with a 2014 Yamaha F70. I get 42 mph top speed with a light load (2 adults, 9 gallons of fuel and some light gear). My motor is mounted 2 holes up.
1985 15’ Sport with Yamaha F70

Simon
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Re: SPORT 15 with F70

Postby Simon » Sun Jul 07, 2019 11:51 pm

TFrere wrote:I’m turning 6000 RPMs with the SCD3 13.25 x 17. My boat is a 1985 15 Sport with a 2014 Yamaha F70. I get 42 mph top speed with a light load (2 adults, 9 gallons of fuel and some light gear). My motor is mounted 2 holes up.


Thanks TFrere! My motor is mounted two-holes-up as well. I might give the 16-pitch a try to see if the engine hits the 6200-RPM range with two adults and light gear.
1987 15' Sport CC

flymo
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Re: SPORT 15 with F70

Postby flymo » Mon Jul 08, 2019 8:25 am

I have tried both the 16-pitch and 17-pitch. I ran the 16-pitch for a couple of years and loved it: great midrange acceleration and holds plane very well. However, when running light and fast I could hit the rev limiter at 6450-RPM and 43-MPH. Even before that the engine felt like it was running out of breath a bit. I switched to the 17-pitch, and I didn't notice any negatives. I have not really been able to do much fast running yet to check out the top end.

To me, the choice between 16- and 17-pitch would depend on: how heavily the boat is typically loaded; whether the engine runs at WOT very often; and if you want that last increment of speed. In retrospect, I probably should have saved my money and stuck with the 16, as I really don't make use of the top end all that much, and I'm a good load just by myself.

Simon, if I am remembering right your boat was always pretty fast. If you want to try the 16, and end up feeling you should have gotten the 17 I'll be happy to swap you.

Simon
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Re: SPORT 15 with F70

Postby Simon » Thu Jul 18, 2019 12:03 pm

flymo wrote:I have tried both the 16-pitch and 17-pitch. I ran the 16-pitch for a couple of years and loved it: great midrange acceleration and holds plane very well. However, when running light and fast I could hit the rev limiter at 6450-RPM and 43-MPH. Even before that the engine felt like it was running out of breath a bit. I switched to the 17-pitch, and I didn't notice any negatives. I have not really been able to do much fast running yet to check out the top end.

To me, the choice between 16- and 17-pitch would depend on: how heavily the boat is typically loaded; whether the engine runs at WOT very often; and if you want that last increment of speed. In retrospect, I probably should have saved my money and stuck with the 16, as I really don't make use of the top end all that much, and I'm a good load just by myself.

Simon, if I am remembering right your boat was always pretty fast. If you want to try the 16, and end up feeling you should have gotten the 17 I'll be happy to swap you.


Hi there,

I plan to order the SCD3 in 16 pitch very soon. I'll contact Ken at prop gods. If it doesnt work out and the 17 pitch may be better for my boat I'll be happy to trade with you.

Simon
1987 15' Sport CC

Simon
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Re: SPORT 15 with F70

Postby Simon » Wed Aug 21, 2019 12:05 pm

So last weekend I had the opportunity to test out the Powertech SCD3 13x16. Compared to my Yamaha aluminum 17" K series prop, it performed much better all around. The hole shot is quicker, I can feel way better acceleration in all rpm ranges, and was able to reach little over 6000 rpms with almost zero trim.

The boat was loaded with 2 people (150 & 140 pounds each), 3 lead flooded batteries, bow mount trolling motor, full cooler on bow, 18 gallons of gas and fishing gear. Tested at lake berryessa on a very windy day so the chop made it hard to do WOT speeds. It was very noticeable that the boat rides much better with less bow oscillation, and it kept the bow much lower and stable when under way.

When I trimmed the motor up about 1/4 of the way, the boat accelerated much faster than the aluminum prop. With the powertech SCD3 13x16 I was able to reach 40 mph with almost no trim at little over 6000 rpms. I think if conditions were much calmer I can reach 6300 rpms and about 42 mph. Certainly happy with the performance so far, however I need to do more testing. Will report back soon.

Simon
1987 15' Sport CC

biggiefl
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Re: SPORT 15 with F70

Postby biggiefl » Wed Aug 21, 2019 2:51 pm

We all know 4 strokes like to be propped to reach high in the band of their redline. I like to prop my boats so that with just me, 1/4 tank or so fuel and ideal conditions and trimmed to the max, I am just at or real close to my redline. If I am 100rpm higher I will usually take it to a prop shop and have some cup added to get it back to redline. This is probably why I get the results I do with performance. Now how often do I drive loaded like that? Enough but we all bring people in the boat and fill the tank to full which still leaves me in the "range" and usually not much lower than redline. ie: redline is 6k and I am at 6k, with 4 people, coolers, bimini top up and fuel I am still touching 5700 I am happy with that setup. I never want to prop with it able to run higher than redline as it really kills your cruise and possibly MPG and no engine should be run higher than is posted.

My point is if you propped your hull to hit redline with the load you described, I think you need more pitch.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

Simon
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Re: SPORT 15 with F70

Postby Simon » Wed Aug 21, 2019 5:34 pm

biggiefl wrote:We all know 4 strokes like to be propped to reach high in the band of their redline. I like to prop my boats so that with just me, 1/4 tank or so fuel and ideal conditions and trimmed to the max, I am just at or real close to my redline. If I am 100rpm higher I will usually take it to a prop shop and have some cup added to get it back to redline. This is probably why I get the results I do with performance. Now how often do I drive loaded like that? Enough but we all bring people in the boat and fill the tank to full which still leaves me in the "range" and usually not much lower than redline. ie: redline is 6k and I am at 6k, with 4 people, coolers, bimini top up and fuel I am still touching 5700 I am happy with that setup. I never want to prop with it able to run higher than redline as it really kills your cruise and possibly MPG and no engine should be run higher than is posted.

My point is if you propped your hull to hit redline with the load you described, I think you need more pitch.


I totally understand what you mean and I've thought about it for a few months while reading almost everything online. It all came down to how I use my boat. It's always loaded with gear and I've never fished alone or driven the boat alone, except for when launching and retrieving at ramp. My redline is 6300 rpms and right now I'm right around 6000 rpms, so with trim it will be close to 6300 rpms and maybe I might still get 43 mph. That's the fastest speed I've ran on the old 17" aluminum. After some more testing, if I keep hitting redline with 2 people then I'll move up in pitch with a trade with Tim.

Simon
1987 15' Sport CC

El Rollo
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Re: SPORT 15 with F70

Postby El Rollo » Thu Aug 22, 2019 10:04 am

Those are impressive numbers, especially with all the gear you have on board.
Everything I hear about the Powertech SCD Props on the 15 Whaler / F70 combo has been good.
I have the same hull / motor as you but running a Bobs 5" manual jackplate and a 4 blade prop.
The set up allows me to raise the motor quite high for running in shallow water.
Last Saturday I ran my 15 on the Colorado River from Blythe California down to Lake Martinez and back, which was 130 mile round trip.
There was a fuel stop half way at a place called Walters Camp.
The water is very shallow with sandbars the entire way, having the jackplate raised up really helped out.
Interestingly I have almost raised the motor to it's maximum height. If I trim out the motor too far I'm just starting to see the water pressure drop.
The prop however is still gripping good when raised up and trimmed out.

biggiefl
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Re: SPORT 15 with F70

Postby biggiefl » Thu Aug 22, 2019 10:57 am

Good that you have a water pressure gauge with a jackplate. I had a 15 with a 70 OMC and my best was 48.6 on GPS. I had a 15 with a 60 OMC 2cyl w/o PTnT that would do 41+. I had a 15 w/o PTnT with a 48spl that would do 36+. I am very disappointed with the top speed of the 4 strokes I am seeing so far on 15's. I had a 70 Suzuki 4 stroke on a 5" jackplate that would almost hit 40.....on a NewTauk 17'. I am half tempted to buy my 5th 15' to experiment with.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

El Rollo
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Re: SPORT 15 with F70

Postby El Rollo » Thu Aug 22, 2019 12:07 pm

You've have a lot more experience than me with the 15 hulls. That OMC 70 sounds like a BEAST.
I'm really happy with my set up for what I do.
I would like to play around a little more with a couple props and jackplate heights. But as i'm sure you know, they're not cheap.
I would like to try the Powertech SCD 4-blade to see how it compares to my FX 4-blade.
Fully-trimmed out and lightly loaded I have to watch out or I'll hit 6400. I think I'll have some cup put into the FX 4 and get it tuned while it's in there.
The classic 15 hull is such a fun little boat to run, I get comments on it everywhere i go.

biggiefl
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Re: SPORT 15 with F70

Postby biggiefl » Thu Aug 22, 2019 12:18 pm

It was actually the 3cyl 60 with rejetted carbs so not quite sure what the HP was but at least 70. I had another with a 70 Evinrude and she did around 44-45 but was mounted in the blind holes. I bought it as a flip so did not bother. 3 blades are faster than 4s....usually.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

El Rollo
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Re: SPORT 15 with F70

Postby El Rollo » Thu Aug 22, 2019 12:37 pm

The way I set mine up for fishing has some weird weigh distribution going on. When I initially set it up I had a Yamaha
3-blade Performance series 16" pitch which was faster, but the bow would porpoise too much when I was trimmed out.
I had some credit at a shop, so I tried the 4-blade and it really helped the porpoising a ton. I know it's a band aid of sorts but I've got the boat set up the way I like it. I have not got a gps speed on it yet, as I'll probably be disappointed. I'm guessing high 30's. Now you've got me interested to go
down and keep testing.

flymo
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Re: SPORT 15 with F70

Postby flymo » Tue Sep 10, 2019 7:38 pm

Simon, just getting caught up with this thread - glad you're having fun with the SCD-3! It really wakes the motor up, doesn't it? As you mention, acceleration is much better at every speed, but even more importantly you can hold plane at much lower speeds. I was out with my wife today in variable conditions and the ability to quickly throttle down and back up was very helpful - she does not like getting bounced around!

It's interesting - the SCD-3 is an update on the much older semi-cleaver design, but the lower blade area and low rake really works well with the F70 on a 15.