Montauk with Yamaha 115

Optimizing the performance of Boston Whaler boats
surveyingdawg
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Montauk with Yamaha 115

Postby surveyingdawg » Mon Jun 08, 2020 9:46 am

The previous engine was an E-TEC 90 H.O. with a 25-inch shaft. A 5-inch jack plate was used to [raise the engine mounting to the proper position].

Now mounting the Yamaha 115 20-inches, the [anti-ventilation] plate is about 3-inches above a extension of the hull.

The engine mounting can be lowered about 2-inches, but will require either using a jack plate or drilling new holes.

Will this setup be too high?

Should I lower it?

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Phil T
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Re: Montauk with Yamaha 115

Postby Phil T » Mon Jun 08, 2020 9:59 am

The anti-ventilation plate is directly above the propeller, and it needs to be 1-1/2 to 2-inches above the bottom of the keel. Typically this is expressed as two-holes-up or three-holes-up engine mounting height, when [the transom has been drilled] using the standard BIA bolt pattern.

Bottom line, you need to be down at least 3-inches from the old engine.

Setback exacerbates porpoising.

At either 377 or 402-lbs, depending on the model year of the 115, the engine is fairly heavy. The easiest way to mount the engine is to remove the bracket and fill the lower holes (use plugs NOT dowels) and re-drill the lower holes. Get some hardwood plugs at a woodworker supply store, dip them in epoxy, insert. Shave off excess. Cover end with Locktite Marine epoxy in white which dries to a very close Desert Tan.

For the lower engine mounting holes in the transom drill at the green or [yellow positions as shown below], and start with the engine mounted two-holes-up, that is, put the top bolt in the third hole counting down from the top.

EngineDrillHoleTemplate.png
Figure 1. BIA Engine Mounting Hole Location Diagram.
EngineDrillHoleTemplate.png (105.9 KiB) Viewed 3957 times
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003

biggiefl
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Re: Montauk with Yamaha 115

Postby biggiefl » Mon Jun 08, 2020 10:34 am

I am confused. How is a 20" shaft engine 3" above the keel? Is it still on the jackplate? Can it be lowered a bolt hole? Have you tried driving it yet? I have both of my outboards mounted ALL the way up on the standard pattern Phil shows above with no problems with performance.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

jimh
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Montaul with Yamaha 115

Postby jimh » Mon Jun 08, 2020 10:35 am

I don't clearly understand the situation you have now with regard to the mounting the 115 engine. Give more information about how the 115 is mounted.

surveyingdawg
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Re: Montauk [17] Yamaha 115

Postby surveyingdawg » Mon Jun 08, 2020 11:18 am

The F115 SHO weighs 377-lbs. I'm sure it is lighter than the E-TEC 90 H.O. with the jack plate.

I plan to finish the rigging and I hope [I can] try out [the boat with new engine]. Thank you for the help.

jimh
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Re: Montauk [17] Yamaha 115

Postby jimh » Mon Jun 08, 2020 1:25 pm

surveyingdawg wrote:I plan to finish the rigging and...try out [the boat with new engine].


Let us know in a follow-up post to this thread what behavior you encountered. Also clarify the several questions asked of you regarding exactly where and how the new Yamaha V MAX 115 SHO engine is mounted on your MONTAUK 17. The actual mounting of the new engine has NEVER been clearly described, so readers do not have any clear idea of how the engine has been mounted and what the engine mounting actually will be when in the future you conduct your performance trial.

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Phil T
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Re: V Max SHO 115

Postby Phil T » Mon Jun 08, 2020 1:39 pm

The new engine to be installed is a V Max SHO 115 and not a F115 per Yamaha. While it the V MAX SHO 115 is a four-stroke engine, the naming is different than the other 115hp engine, the F115.

The V MAX SHO 115 does have a dry weight of 377lbs, same as the F115.

In reviewing the website specifications, both models are identical. Clear as mud.
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003

biggiefl
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Re: Mounting height

Postby biggiefl » Mon Jun 08, 2020 2:00 pm

I ran my Suzuki 4 to 4.5-inch above the keel on a 5-inch setback jackplate. The SHO is more high performance and meant to run higher with a low water pickup You might be OK at [with the current mounting that has been described as placing the anti-ventilation plate about 3-inches above the keel].

Can you take some pics of your setup?
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).