15-footer with Surface Propeller Running

Optimizing the performance of Boston Whaler boats
Jamesgt727
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Joined: Thu Jan 28, 2016 9:38 am

15-footer with Surface Propeller Running

Postby Jamesgt727 » Tue May 31, 2016 11:37 am

See: https://youtu.be/mLnAsLlhfVc

Two years after the fact, finally recorded it. It's a 28-pitch cleaver on a hot 90 Mercury. No manatees harmed.

Jefecinco
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Location: Gulf Shores, AL

Re: 15-footer with Surface Propeller Running

Postby Jefecinco » Wed Jun 01, 2016 10:16 am

Why no over the transom video? We want to see that surface prop in action.

What speed were you making?
Butch

Jamesgt727
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Re: 15-footer with Surface Propeller Running

Postby Jamesgt727 » Wed Jun 01, 2016 2:40 pm

I'm guessing that with two people on the gear, before the motor was trimmed it was doing mid to high 40's. As soon as the trim comes up, it accelerates like its turbo-charged. In the video, the boat is going fastest at the end just past the turn it got its legs under it. Maybe 55. The first rooster tail, I had the prop up a bit too high.

jimh
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Re: 15-footer with Surface Propeller Running

Postby jimh » Fri Jun 03, 2016 9:41 am

Running at 50-MPH or more in a small boat like a classic Boston Whaler SPORT 15 with its very low-to-the-water seating must feel like flying. I used to get a rush when making 34-MPH in mine.

Jamesgt727
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Re: 15-footer with Surface Propeller Running

Postby Jamesgt727 » Fri Jun 03, 2016 11:00 am

Jim,

That Merc is underrated. A few small mods woke it up and it makes power. The prop it's spin gin is a 14.5"x28" cleaver. It's a nutty mix, basically a surfboard, with a half of a 300, sitting on a wood plank. I'll tell you though, the hull mods made to this boat make it run flat and true. It's pretty fast for a 15. When I am by myself, the hot rod jet skis can't keep up.

Binkster
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Re: 15-footer with Surface Propeller Running

Postby Binkster » Sun Jun 05, 2016 8:58 am

In your video, I noticed the boat was porpoising pretty good when you kicked the motor out a bit. Actually that was probably the right setup, but that's what happens when you put a performance motor on a non performance hull. It would be better suited on a Donzi Sweet sixteen, and quite a bit faster. Remember Mick's (runpastthefence) 15 footer with a modified 135 OMC. Now that was really goofy.

rich

Jamesgt727
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Re: 15-footer with Surface Propeller Running

Postby Jamesgt727 » Sun Jun 05, 2016 10:43 pm

Bink, the porpoise was caused by jumping a 22' boats wake. Pretty sure we went airborne, --I laugh aloud--. You can see it in the video

Jamesgt727
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Re: 15-footer with Surface Propeller Running

Postby Jamesgt727 » Sun Jun 05, 2016 11:00 pm

Bink, I read his posts, saw he started with a 90hp V-4, but I never read anything about a power head rebuild or a swap. Then the last post I saw it had a 200 cowling on it, but it had the same mid and lower unit. I know the cowlings all fit the same pan. I wish he was still around, love to know how he kept it from sinking, --I laugh aloud--. Mine takes on water just standing in the back with a full tank of fuel. I have to ballast mine now with weight in the front locker. The hydraulic jack plate adds 40 lbs, but it's the only way to go fast with a big prop is to get it out of the water

Jamesgt727
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Re: 15-footer with Surface Propeller Running

Postby Jamesgt727 » Mon Jun 06, 2016 2:41 am

Bink, I don't know if you saw this video, tell me what u think of the build details. I know you like 15's and custom touches

https://youtu.be/lf-aEBGcHaI

runpasthefence
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Joined: Tue Jun 07, 2016 4:57 pm

Re: 15-footer with Surface Propeller Running

Postby runpasthefence » Tue Jun 07, 2016 5:30 pm

Daaaang. That one's a looker. Almost made me go look in the back yard to make sure mine's still under the tarp.

Jamesgt727
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Re: 15-footer with Surface Propeller Running

Postby Jamesgt727 » Wed Jun 08, 2016 5:35 pm

Howdy Mick, when I first showed my build, people referred to your boat so many times it's not even funny. Btw, I love what you did. I can't believe how similar the boats were in concept of the hull, etc. Get that thing water ready, the guys on the go fast website, are organizing a Boston Waler speed shootout. Not sure when it's gonna take place, but sounds like the next big river run in north Florida. I'm trying to figure out how to get anoth 15 mph so I can just keep up. Either my motor is going to get modified more, or I am going to change motors to a V-6, like a 200xs or something crazy. A couple of the guys on there are big spenders and a win at all cost guys. I think it would be cool to win the title, but with this crowd that will be tough. I hear someone has a 17 with a 280 on it that may have seen 80. It'll be fun though. Get her wet and running soon.

runpasthefence
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Re: 15-footer with Surface Propeller Running

Postby runpasthefence » Wed Jun 08, 2016 10:17 pm

Wait, what?! I always thought a Whaler shootout would be admirable. I used to pitch that idea to anyone who'd listen. Do you have a link?

My boat is just a bare hull right now. It fell into disrepair while I was overseas, and when I came back motorcycle and old truck projects held most of my attention.
I ran a hot V4 Yamaha and eventually a 2.6L Yamaha V6 previously. I think you're on the right track. If I were to shoot for high numbers again, I'd be looking for a light Mercury 2.4, but the boat sits languishing under a tarp for now. I've often thought of building a mild three cylinder Yamaha. The V4 and V6 truly made it a single-person boat, and a 260ish pound motor makes for a much milder ride, but there was nothing like having a cruising speed of 50-55mph with the big motors. I've got a big Whaler now, so maybe I'll get back into the speed game one day.

Let me know how your search for speed goes. If you break the low 70s maybe that'll light a fire under me, and maybe we'll have a good ol' fashioned arms-race.

Binkster
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Re: 15-footer with Surface Propeller Running

Postby Binkster » Thu Jun 09, 2016 1:41 pm

I don't understand what the point of all this is when the speeds you are talking about is so easily obtainable with a hull made for that purpose.

rich

Jefecinco
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Location: Gulf Shores, AL

Re: 15-footer with Surface Propeller Running

Postby Jefecinco » Thu Jun 09, 2016 6:58 pm

Maybe it's a little bit like the hot rod days in the fifties and sixties and even today.

Anyone with the means could buy a factory hot rod. High performance Corvettes come to mind. Others, perhaps with less means but some skills could take a family car and spend a lot less money but a lot more time and effort and create a "sleeper" that would run away from a Corvette.

Sleepers were great fun and separated a lot of factory hot rod owners from a pretty good bit of cash.

Not quite the same, I know, but maybe the challenge aspect is very similar.
Butch

Jamesgt727
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Re: 15-footer with Surface Propeller Running

Postby Jamesgt727 » Sun Jun 12, 2016 9:50 am

I think the answer to binks question is simply one word:

'merica


Jefecinco
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Re: 15-footer with Surface Propeller Running

Postby Jefecinco » Fri Jun 17, 2016 8:58 am

That's a nice little Johnny Bass Boat. Should fly right along with the big boys.
Butch

alfa
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Re: 15-footer with Surface Propeller Running

Postby alfa » Tue Jun 21, 2016 2:05 am

Very nice 15'.
Sweet hull, congrats.

Alain

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dg22
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Re: 15-footer with Surface Propeller Running

Postby dg22 » Thu Jun 23, 2016 11:27 am

Jamesgt727, Nice boat and setup. That is one of the nicest 15 footers BW I've ever seen. Enjoy!

Jamesgt727
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Joined: Thu Jan 28, 2016 9:38 am

Re: 15-footer with Surface Propeller Running

Postby Jamesgt727 » Fri Jun 24, 2016 7:21 pm

Thank you sir, we put a lot of love and effort into this little boat. We enjoy the heck out of it. Thanks again, see you in the water!