1988 Montauk 17 Re-power

Optimizing the performance of Boston Whaler boats
greenbean
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1988 Montauk 17 Re-power

Postby greenbean » Mon Apr 24, 2017 2:42 pm

[On a 1988 MONTAUK 17 the author says he] needs to replace the original [1988] Yamaha 90-HP two-stroke-power-cycle outboard engine. What are the best options?

[Nota Bene: the thread has been moved to PERFORMANCE forum to join all the other threads that discuss re-powering of classic Boston Whaler boats.--jimh]

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Phil T
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Re: 1988 Montauk 17 Re-power

Postby Phil T » Mon Apr 24, 2017 3:19 pm

Typical recommendations are (in NO order of preference):

90 hp options:
Mercury Fourstroke 90
Yamaha F90
ETEC-90

70 hp options:

Yamaha F70

The questions you need to answer include:
---Which service providers do you have in your area? Are they any good?
---Do you want to save money by re-using your existing controls and gauges or don't care (add 1k).
---Do you live in a cold climate (winter w/below freezing temperatures). If so, ETEC winterization mode is ideal.
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1992 Outrage 17, 1992 Evinrude 115

frontier
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Re: 1988 Montauk 17 Re-power

Postby frontier » Mon Apr 24, 2017 9:27 pm

The 90 HP 2-Stroke Yamaha is the perfect engine for a classic Montauk. Lightweight and great quality, power and speed. Try to find a good used one. There are lots out there - Yamaha made them from c.1980r through c.2008. My [second] choice would be a new F70 Yamaha.

greenbean
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Re: 1988 Montauk 17 Re-power

Postby greenbean » Tue Apr 25, 2017 8:29 am

Not sure I'll be happy with the Yamaha F70 after having the 90. Has anyone gone from the 90 to the F70? How's the performance?

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Phil T
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Re: 1988 Montauk 17 Re-power

Postby Phil T » Tue Apr 25, 2017 9:11 am

Boston Whaler owners have reported with the engine is installed at the appropriate height (2-to-4-holes-up depending on engine and propeller) and a stainless steel propeller, a lightly loaded Montauk with one person, 6-gallons of fuel should attain wide open throttle (WOT) speeds of:

90 hp: 42-45 mph
70 hp: 36-39 mph
Last edited by Phil T on Tue Apr 25, 2017 11:58 am, edited 1 time in total.
Member since 2003
1992 Outrage 17, 1992 Evinrude 115

jcdawg83
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Re: 1988 Montauk 17 Re-power

Postby jcdawg83 » Tue Apr 25, 2017 11:47 am

I put an E-TEC 75 on my classic Montauk, it runs great, and I've been very happy. That said, I rarely have more than two people in the boat. If I were going to regularly carry more than two people or heavier loads than a cooler full of ice, a tank of fuel, and fishing rods and tackle, I would definitely want a 90-HP engine. I don't pull any skiers but I think it would be fine with children, not so sure about adults.

My 75 cruises at around 25 mph at 3500 to 3700-RPM and is incredibly easy on fuel. I think I average around 6 to 7-MPG at cruise speed. Top speed with a 15" pitch aluminum prop is around 35-MPH I think my top speed might be a little higher if I switched to a stainless prop.

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Re: 1988 Montauk 17 Re-power

Postby jimh » Tue Apr 25, 2017 12:51 pm

If 90-HP is the criterion for re-power, give very careful consideration to the E-TEC 90-HP three-cylinder engine. It has often been the choice for re-powering a MONTAUK, perhaps more than any other engine.

The E-TEC's modest weight is a very good match for the hull. I would expect the performance from the E-TEC to exceed the performance from your 1988 Yamaha 90-HP engine. The older Yamaha engine has quite modest displacement and was never thought to be a powerhouse. I think it had only 950-cc displacement. The E-TEC 90 has 1,295-cc displacement. Its power band is excellent due to direct fuel injection.

Four-stroke-power-cycle engines tend to have limited power bands, unless forced induction methods like supercharging or turbocharging are used. The 90-HP output of a non-forced-induction four-stroke engine typically occurs only at maximum engine speed, that is, at the very highest RPM. With the E-TEC 90 the peak power output occurs over a wider range of engine speeds, and you will have more power available at lower engine RPM.

I have driven a c.1988 MONTAUK 17 with an E-TEC 90. I was very impressed with the engine performance. I consider it to be among "the best options."