1982 Montauk 115 HP

Optimizing the performance of Boston Whaler boats
MikeF1
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Joined: Wed Feb 03, 2016 12:26 pm

1982 Montauk 115 HP

Postby MikeF1 » Wed Feb 03, 2016 12:44 pm

[This inquiry seeks advice about propeller selection for a 1982 Boston Whaler MONTAUK with a 115-HP Mercury outboard engine using the infamous 2+2 displacement on demand method--jimh] No flames about the engine please. It came with the boat and runs fine. The current aluminum propeller has a bunch of dings and I'm thinking of going to a propeller made of stainless steel. I mostly just cruise with some towing of tubes. [The MONTAUK with 115-HP] currently does 43-MPH or faster, depending on load. I don't often go to wide-open throttle, but it's fun when I do. There's a boat show in town this weekend and I may be able to get a deal. I've never been to one before so I don't know how likely that is.

Mike

jimh
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Re: 1982 Montauk 115 HP

Postby jimh » Wed Feb 03, 2016 2:32 pm

Do you have any information about the model of the propeller you are using now? Its pitch? Its diameter?

Do you have a tachometer to measure the engine crankshaft speed?

What is the gear ratio of your engine?

A good place to start selection of a replacement propeller will be to get something similar to the present propeller, as your report of 43-MPH top speed sounds reasonable for a MONTAUK with a 115-HP engine.

To get a comparison of what sort of boat speed at full-throttle might be appropriate for a classic MONTAUK 17 with various horsepower engines, see

http://continuouswave.com/whaler/refere ... power.html

MikeF1
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Joined: Wed Feb 03, 2016 12:26 pm

Re: 1982 Montauk 115 HP

Postby MikeF1 » Thu Feb 04, 2016 10:22 am

I don't have the numbers handy and the boat is in winter storage.

I'm not sure if the increased cost of SS would justify any increase in performance. The tach says 5200 WOT which is right on the numbers for this motor. From what I've been reading, dropping 2" in pitch when going to SS seems to be the norm.

jimh
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Re: 1982 Montauk 115 HP

Postby jimh » Sat Feb 06, 2016 9:45 am

[I deleted a sidebar discussion on a topic not related to the performance of a 1982 Montauk with 115-HP]

jimh
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Re: 1982 Montauk 115 HP

Postby jimh » Sat Feb 06, 2016 9:46 am

MikeF1 wrote:I'm not sure if the increased cost of SS would justify any increase in performance.


Propellers made of steel are more durable than ones made from aluminum, so their increase in cost often returns some of that investment when the propeller survives intact a minor strike with some debris in the water or some bottomland which would have damaged an aluminum propeller.

jimh
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Re: 1982 Montauk 115 HP

Postby jimh » Sat Feb 06, 2016 10:59 am

MikeF1 wrote:The tach says 5200 WOT which is right on the numbers for this motor.


Ah, good, you have a tachometer. That will make it much easier to evaluate the propeller selection.

That the present propeller allows the engine to accelerate to its recommended maximum crankshaft speed means that the propeller is a good match for the engine and boat combination, but, since you do not seem to know any of the propeller dimensions, we cannot really get too much useful information from this data. Perhaps you can make a visual inspection of the current propeller and find some markings on it that will reveal its pitch and model designator. You can deduce the diameter from measurement of the blade-tip to hub-center length.

MikeF1
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Joined: Wed Feb 03, 2016 12:26 pm

Re: 1982 Montauk 115 HP

Postby MikeF1 » Mon Feb 08, 2016 1:29 pm

The current prop is a Quicksilver 13" x 19". One guy recommended a Stiletto 13 1/4" X 19 " SS but elsewhere I've read to drop 2" in pitch when going SS.