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I have a 1984 15 super sport, powered by an f60 yamaha. It has been fine for 4 or 5 years but very slow out of the hole,it takes 8 to 10 seconds to get on a plane. I was wondering what I can do to help it plane off quicker? Thank you for the help!

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Look at your wieght distribution. If you are nose heavy or trimmed wrong thqatb may be your problem How much gas you carry and where. Its seven pounds agallon!

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The tank is mounted under the rear seat, it hold 12 gallons. The only thing in the front is the anchor, life jackets and cooler. The battery is mounted directly behind the captains seat. The motor still has the stock prop. I leave the motor trimmed most of the way down until it is planed off then trim it up some.

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JG, can you clarify what prop you have on there? There really is no such thing as a "stock" prop - I expect you mean a Yamaha-branded aluminum prop, but if you can clarify model and pitch that would be helpful. You may see some ID numbers on the prop hub that will let us discover what it is.

Please also describe how the motor is mounted on the transom. Is it all the way down as low as it can go (upper bolts in the top hole)?

Also, do you have a tach and a GPS to measure speed? It would also be helpful to know your RPM and speed running wide open.

I am sure you can improve the situation with a different prop, and possibly raising the motor - the more data you can provide, the better.

Tim

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I am currently out of town for work but will be home tonight to look at the prop and how high it is mounted on the transom. I have a tach, a speedo, and a GPS. I had it out Saturday with the motor almost all the way down it won't push past 4600 rpms at WOT. The more I trim the motor (after getting on a plane) the faster it goes and the more rpms obviously. I think I topped out at 6200 rpms on my tach and I was pushing 44mph. The motor was trimmed up pretty high shooting a rooster tale. Thanks for all the help!

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Interesting - that's certainly an excellent WOT speed. I am fascinated by the difference in speed with trim - 4600 to 6200 is a really, really big range. My first thought is your current prop has the correct pitch, but too much blade area, which is bogging you down until the motor gets spun up to RPM.

For reference, I'm by no means an expert, just another 15 pilot who did some amount of experimenting with props on my own SuperSport.

Tim

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I really appreciate the help tedious. The prop read 15-G. I was not able to make it home so my girlfriend could not tell me how high up the motor is mounted. What do you thing about getting vent holes drilled in the prop? would a hydrofoil help me any?

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It sounds like this boat can handle a Mercury "Trophy Sport" 4 bladed prop, assuming the engine has the small gearcase (which it should have for an application like a 15' classic Whaler) For the small gearcase 40-60 Mercs, and 50-60 Yamahas, which have the same powerhead, this is the fastest prop you can buy, period. Has both superior hole shot and fast top end. Do some research on it. This prop lets a Merc 60 run neck and neck with a Yamaha F70 equipped with conventional SS Yamaha prop (which is why Mercury never bothered to bring out a competing 70 on the same block, as Yamaha has done).

You can have one delivered to your door for $279.

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I will definitely take a look at the four blade prop after tomorrow. I pulled the prop today and put it on the drill press and drilled some vent hole in it. I figured I would give it a try before I ordered a new prop or wasted money on the smart tabs.

I also looked at the motor it is on the second hole up. The cavitation plate is almost even with the keel, maybe a half inch higher.

I also found a crack in the keel leaking water so I am going to have to drill some holes tomorrow and see how saturated the foam is. My boat might be sitting heave due to the foam being soaked. I have a lot of problems. Any advice on drying foam would be appreciated.

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What is the second hole up?

Looking at the cavitation plate and guessing or measuring does not work that well.

See this article and let us know exactly where your motor is mounted.
http://www.whalercentral.com/articles...cle_id=106

Is your motor mounted 1, 2, or 3, holes up?

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Sorry for the typo I meant two holes up, I was on a work call when and not paying attention. I just walked out and measured, the cavitation plate is about 3/8 inches above the keel.

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Outstanding.

2 holes up is all we need to know for the Yamaha F60

Now we can go from there.

Again, everyone may measure differently so it really doesn't matter any longer. Hole mounting matters.

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Ugh, sorry to hear about the crack - that sure could have an effect. Your mounting height sounds good.

Interesting thought on drilling vent holes, and certainly worth a try. If I understand the theory, they let the prop ventilate a bit during initial spinup, effectively providing a lower gear at takeoff. I'll be interested to see your results.

I have no direct experience with the prop Finnegan mentioned, or any 4-blade prop for that matter. in general, I see more blades and more blade area as a way of providing additional traction in situations where someone has plenty of power, but not enough grip on the water. it seems to me your situation is the exact opposite.

I would not even consider a foil - would only use that as a last resort, if all else fails.

Repairing the crack and trying the newly-vented prop seem like good next steps - let's hear the results and go from there!

Tim

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I will be sure to let you guys know how the vent holes work. i might also order a set of the smart tabs to help the vented prop. I am going to drill some holes and let the foam dry out as much as I can before I can try the prop. I will keep everyone posted on the vent holes. Thank you for all the help!

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Maybe the smart tab holes will let some water out!

More seriously, I'd optimize the prop before adding additional tabs or heaven forbid, a fin - at no time during my journey of prop discovery did I ever feel that tabs would have helped me.

Tim

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This is your only thing to focus on.

Forget the engine height, prop, foil, tabs etc.

Pull the boat out and let the water drip out. When it stops, empty the boat of everything removable and take it to a truck scale and get a weight of the boat and trailer.

Take some photos of the damage, the engine height and the hull and post them so we know what you have to deal with.

Report back.

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You can try sucking water from the crack with a shop vac.

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Smart tabs will be my last resort and a foil is out of the question. I have drilled some holes and the boat is currently drying. I will post some pictures this afternoon of the damage. It wasn't a huge crack so I am going to see just how the water made it. I just found the shop vac idea and I have a few. I might try running two or three overnight. I will run it across a scale as soon as it is done drying. thank you for all the help guys I will keep everyone updated!

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Good luck on the dry down! I just swapped the 10" x 15" 3 blade aluminum on my 1988 15 SS, with a 2002 Honda BF50, to a Solas 4 blade 10" x 14" stainless and all I can say is 'Wow!'

Absolutely love the hole shot and load carrying/lifting power!

Long overdue as we use this boat to access an island home. This is the workhorse boat so we need it to do it all.