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This site was recommended to help me with my problem.

I repowered my 1968 16.7 Whaler center console with a 2011 F70 Yamaha because I wanted the lighter motor. The marina first tested it with a 13 x 16" polished S/S prop and it only turned up to 4900rpm. Per Yamaha's formula the next prop they ordered was a 14 x 11 aluminum. Water testing proved the boat was going nowhere @ 6300rpm. They repropped with a 13 5/8 x 13k aluminum prop and did the PMI saying it hit the 6300rpm comfortably. I have water tested the boat and I'm only doing 14mph @ 4000 and 20mph @ 5000. When I looked at Yamaha's website, boats that were heavier by 300 pounds and longer/wider were running 13 x 14 painted S/S or 13 x 15 aluminum and getting the speeds I used to get, about 27mph @ 5000rpm and 36 @ WOT. The shop already has 1 prop on the shelf because of an error (Yamaha's at that), I'd like to make sure it is only one more as I will stick with whichever prop I order next.

The shop will take my 13 x 13 aluminum back if I want a larger prop. I'd really like to get the 13 x 15 aluminum but concerned that it is too close to the 13 x 16 S/S they first tested and couldn't get the rpm's over 5000. Also the motor is mounted with the cavitation plate 1" above the bottom of the hull using the 2nd mounting hole from the top on the bracket. It could be lowered if necessary.

Has anyone repowered their 17 whaler with this new motor and what prop gave you the best performance? The shop will order any prop manufacturer since the prop isn't required to be Yamaha brand.

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Metalcaster repowered his 16'7 with the F 70.

Tom Cark, our prop guru recommended to mount the motor three holes up and use a 13-1/4" x 15" Stiletto Advantage 4.25

This is not a guess, Tom's advice is dead on 99.5% of the time.

Here is the thread:
http://www.whalercentral.com/forum/vi...d_id=13409

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Couple of things, 1st the 70 hp is the smallest engine recommended for a 17 whaler so do not expect blazing speeds, Next the Boston Whaler is not a race design hull. Again are you sure the whaler is not water logged...And yes Tom is usually right on...

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Thanks thus far. I read the other post and here is what I can offer additionally. I drilled weep holes in the hull and it sat for well over 12 months that way while I did the other work on it. I cut the old galvanized rigging tube out of the hull and replaced it. When I had the inside exposed there was very little indication of water down the midline of the keel so I am pretty certain it isn't waterlogged. The boat ran 36mph with a 2 stroke 90 that had bad compression. Probably would run more but the porpoising at 36 was bad enough, I didn't want to see what the remaining throttle would do. I saw a Key West 177 skiff with an F70. Specifications on Yamaha's power matched performance sheets show that boat is bigger but probably about the same test weight. The hull configuration is much closer to a Whaler than other deep-V models but definitely isn't flat like a Carolina Skiff.

Using a 13 x 15 aluminum prop it's getting the numbers I used to get. I think I should be somewhere close to those performance numbers with a prop change.

Now the Stilleto is a S/S Mercury prop? The mounting hole location, is that counting from the top of the bracket or the bottom?

Before someone jumps on the F90 story, my friend repowered his 17' Montauk with the F90 and now his scuppers in the engine well sit below the waterline. My 16 is shorter and almost a 1' narrower in beam than the Montauk. The shop put an F70 on a 15' Montauk and said it was a 40+ boat. Those are the reasons I went with the F70 over the F90.

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See this "Article" on WhalerCentral for motor mounting heights.
http://www.whalercentral.com/articles...cle_id=106

NOTE:
The Montauk 17' and your 16' 7" hull are the same length and width.....

The newer Montauk 170 is a different hull completely if that is the one you are comparing yours too...

My choices on new power for a 16/17 Classic hull are:
E-Tec 90 2 stroke
Yamaha 70 4 stroke

The choice you made was a good choice in my opinion....

Here are the complete Current Engine Choices and their weights
http://www.whalercentral.com/articles...ticle_id=5

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The keep the record straight, a 70 hp engine is NOT the lowest horsepower recommended.

Depending on the model of the 16'7 hull, a 40 hp is the "minimum horsepower to plane" recommended by Boston Whaler.

For the mounting height suggested, the top bolts should be in the fourth hole down from the top hole.

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Yes...
To find out the specifications from the Boston Whaler catalogs, we have most of that information posted in our "Whaler Models and Info" link on the left sidebar.
http://www.whalercentral.com/userphot...allery.php

For me, I would not have wanted anything less than a 70 hp and that is what I highly recommend.... 70 or 90....

Maximum is 100 hp but I don't think any 100 hp are being made at this time.

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The minimum recommended power for a 1968 16'-7" model is 35 HP and that was back when horsepower was measured at the powerhead, not the prop. 70 HP is plenty and the F70 has been very well received by classic Whaler owners who have bought it for repowering their boats.

At any rate, the question is NOT what power do you recommend for this boat but what propeller to use with this motor that has already been purchased? With the motor mounted as high as it can go and a 13-1/4" x 15" Stiletto Advantage 4.25 installed, I predict a top sped of 38 MPH.

The Stiletto Advantage is a stainless steel propeller. The Advantage is not a Mercury brand propeller, it is a Stiletto brand propeller. Stiletto propellers are made by Precision Propellers Industries Inc. (PPI) which also makes the Turbo brand propellers as well as almost all the Yamaha brand propellers as well props for as a few other manufacturers. PPI has been owned by Yamaha since 2007.

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I won't even touch the prop question as Tom is way more informed. I have a 1964 and a 1966 with 70hp and 90 hp Yamaha 2-strokes. Just aquired the one with the 90 and it is VERY FAST. I re-powered the other boat with the 70 after having a 70 on it for 25 years and would do the same again. If you want to go over 45 mph in a 16 foot boat go ahead, just never let anyone without a lot of small boat experience use it at that speed.

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I ended up putting a Solas alumiinum prop on my 16'7" whaler. I think it was a 15 pitch. Top speed was 35mph consistently occasionally hitting 36. RPMs right at 6200 or just above.

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Meatlcaster -- What motor do you have on your 16'-7" Whaler? What year and model is your Whaler?

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Metalcaster, I sent you a message about your prop, how high you mounted your motor, and what performace #'s you are getting, I'd be very interested to hear.

Tomorrow or Tuesday I am going to ask my shop to order another prop. Since they agreed to order one for me and exchange this 13 x 13 out, this choice is pretty much going to be on me. I'd really like to get it right. All the test F70's are using a 13x14 painted steel prop. Again, the boat was first tested with a yamaha 13 x 16 performance S/S prop and only spooled up to 4900rpm. Will a 13 x 15 Stiletto get me to 6200-6300rpm so the motor isn't straining?

As far as speed, I'd like to get a 27mph @5000 cruise like the other 17-18' test boats are getting with a WOT of 35+ if I need to beat a storm or something. I put a couple more hours on it and I consistently run 20mph @ 5000 with a WOT of 27mph and an average of 5.6mpg. The test boats with an F70 are averaging 7-8mpg @ 5000rpm.

The motor is mounted in the 2nd hole from the top. How much difference will moving it all the way to the bottom hole make in performance? Will it porpoise more?

It will be due for it's 10 hour service. I can have them move the motor when they change the prop. If I measure off the cavitation plate to the centerline on the transom, how high can the cavitation plate be from the bottom of the keel?

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mlashley, I tried to read your message but couldn't. Don't know why. I tried to send you a message this morning. You can email me and I will respond. rrey89@comporium.net. I have a 69 16'7' custom- was Katama. 70 hp 4 stroke Yamaha running a Solas aluminum prop 13.5 X 15". Occasionally will hit 36 mph with light load. Engine mounted next to highest position.I first tried a Yamaha 13 pitch prop and max speed was 29 mph and rpms ran too high. Porpoising started at around 31 mph. I have a wood deck on the front and a 12 gallon fuel tank under the side console so that adds weight to the front.