Boston whaler repower

El Taco

Almost A Member
May 11, 2014
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Gabriel
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Need some help deciding, I will be repowering my 2006 17' Montauk. Plan is to go with a 90hp Yamaha, but was told that a 70hp outboard might be a better option. There is a 100lb difference and was told that I would only get a few mph difference. I'm open to all suggestions and would love to here 1st hand experiences from whaler owners. Thanks!
 
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rancanfish

wow, how deep is it here?
Jul 5, 2004
633
297
Dublin, CA
Name
Harold Head
Boat
1971 BW Menemsha
I don't think it would be an issue on your modern Whaler. For my 1971 I think the new 70hp is ideal. I would go with a 90hp for your boat. It really depends on your useage. How many peeps, offshore or inshore, etc.

If I could find a Yammie 90hp 2 stroke in good shape I'd use it, but pretty much unobtainium in CA.
 
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El Taco

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May 11, 2014
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Gabriel
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I run max three people for inshore fishing but would only run two for offshore runs. Run solo most of the time. I don't plan on running full throttle so speed is not really a concern. I'm more worried about fuel and performance.
 
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El Taco

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May 11, 2014
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Gabriel
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If the hull can handle the weight, bigger is always better. You can use a little of a lot but you can’t use a lot of a little.
A bigger engine loafing along will use less fuel than a smaller engine working hard in most applications.
Running an underpowered boat simply sucks.
Very true, thank you!
 
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uglyducky

I heard there was gonna be cake?
Dec 5, 2017
605
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Los Angeles
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Jesse Collin
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It's complicated
get as much as your transom can handle and just use whatever you need of it. your fuel economy will more largely be determined by how you run the motor. a 70 vs 90 hp motor isn't gonna be night and day with fuel burn in any case.
 
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michaelfish

Newbie
Aug 14, 2012
52
21
Central Coast
Name
Michael
Boat
170 Montauk
I have a Honda 90 on my 170 and would not consider anything smaller. I think the Honda and Yamahas weigh approximately the same. Whoever told you that a 70 would be a be a better fit was almost certainly thinking that you had a 17' Montauk and not the slightly larger 170 Montauk as stated above. 90s are standard for your hull and some people even go with 115s.
 
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Hellosugaree

Almost A Member
Sep 6, 2019
236
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San Francisco
Name
Timbo
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13' Boston Whaler
Go big or go home.

That should be enough, but if not:

Obviously if you're planning on repowering then you don't have selling in mind any time soon, but if that time ever comes you'll have a harder time selling a boat with less power when there are other ones out there with more. People like bigger numbers, even if it's not necessarily better.

You get better fuel efficiency and maybe reduced engine wear running at lower RPMs to achieve any given speed in your normal cruising range. It's really not that big of a difference though unless you're going from underpowered to appropriately powered.

Here's performance data from a newer 170 Montauk with a 90 vs 115. You can see slight gains in efficiency in mid ranges with larger engine. It's really not that much though. Maybe it would be a larger difference if you compared the 90 to a lower power. This data I think is from 2017 where they are 90 standard, 115 max. Not sure if 2006 has a lower HP rating, but the principle still applies.

90:
Screen Shot 2020-10-05 at 3.08.59 PM.png

115:
Screen Shot 2020-10-05 at 3.09.07 PM.png
 
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El Taco

Almost A Member
May 11, 2014
147
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Gabriel
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Almost
Go big or go home.

That should be enough, but if not:

Obviously if you're planning on repowering then you don't have selling in mind any time soon, but if that time ever comes you'll have a harder time selling a boat with less power when there are other ones out there with more. People like bigger numbers, even if it's not necessarily better.

You get better fuel efficiency and maybe reduced engine wear running at lower RPMs to achieve any given speed in your normal cruising range. It's really not that big of a difference though unless you're going from underpowered to appropriately powered.

Here's performance data from a newer 170 Montauk with a 90 vs 115. You can see slight gains in efficiency in mid ranges with larger engine. It's really not that much though. Maybe it would be a larger difference if you compared the 90 to a lower power. This data I think is from 2017 where they are 90 standard, 115 max. Not sure if 2006 has a lower HP rating, but the principle still applies.

90:View attachment 1208552
115:
View attachment 1208553
My 2006 is rated for max 90hp can I legally put a 115hp which is 10lbs lighter then my outboard now? Definitely going bigger! Thank you
 
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ShadBurke

Just a Guy and his Boston Whaler
Oct 28, 2005
3,685
2,101
Carlsbad
Name
Shad Burke
Boat
22' Boston Whaler Guardian
Montauk 170: I would go with the new lightweight Yamaha F115.

Classic 17 montauk: Yamaha F70 all day every day

Make sure your insurance carrier is good with it as well.
 
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Unassailable

Professional Amateur
Aug 26, 2009
1,356
750
San Diego
Name
John B
Boat
BW
My 2006 is rated for max 90hp can I legally put a 115hp which is 10lbs lighter then my outboard now? Definitely going bigger! Thank you

Get it in writing from your insurance carrier. Your year hull wasn't rated for the 115 as you mentioned. Lighter does not mean your insurance will cover it if anything happens. Insurance salesmen are a dime a dozen and will tell you anything. If they have an agreed upon value including liability with the 115hp motor, go for it!
 
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Pacific Jigger

You’ll never know unless you go
Sep 16, 2019
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Bud
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Formula 233
Don’t do that or any insurance claim will be void if you go over manufacturer recommended HP or transom weight.
^^^This is correct. Not to mention the trouble with the Coasties if you’re checked and motor hp exceeds mfgs rating plate. You can contact Boston Whaler and request a new rating plate, as the 115 weighs 10lbs less. No guarantee they will but I do know that others have gotten new rating plates from other manufacturers.
 
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Vigilant32

BightPatrol
Nov 9, 2004
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Not true. The plate is manufacturer recommended only, not the legal limit.

I’ve run many boats that were above the plate values. No insurance or coast guard issues. The policy needs to match the power you have. Several Coast is boarding and they have never brought up the subject.
 
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uglyducky

I heard there was gonna be cake?
Dec 5, 2017
605
715
Los Angeles
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Jesse Collin
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It's complicated
Not true. The plate is manufacturer recommended only, not the legal limit.

I’ve run many boats that were above the plate values. No insurance or coast guard issues. The policy needs to match the power you have. Several Coast is boarding and they have never brought up the subject.
insurance absolutely has the right to deny a claim if your HP or weight is over factory recommended standards. bc something was not addressed in anecdotal experience doesn't mean it's not factual. i don't know CG rules and regs around this but insurance can def tell you to pound sand.
 
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Vigilant32

BightPatrol
Nov 9, 2004
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insurance absolutely has the right to deny a claim if your HP or weight is over factory recommended standards. bc something was not addressed in anecdotal experience doesn't mean it's not factual. i don't know CG rules and regs around this but insurance can def tell you to pound sand.

Not according to my insurance carrier. And the theory has been tested via claims.
 
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Unassailable

Professional Amateur
Aug 26, 2009
1,356
750
San Diego
Name
John B
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BW
It can be done. You need to make sure your insurance knows and it's in writing. I've had a few discussions about this with my friend who was an underwriter with two very large insurance agencies.
 
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Bwood

Member
Jan 24, 2006
272
429
Laguna Niguel
Name
Brett
Boat
17' Whaler
Just go 90 Yamaha. Just repowered mine. Plenty of power, no issues so far 200hours. 16 gallons burned this weekend from DP to Cat around the back to palisades and up the front to long pinpoint.
 
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