1978 Montauk 17 or 1960 Nauset 16: Re-power with 130-HP

[Soho]

BACKSTORY:
I have a 1969 Nauset 16 with a 2018 Yamaha 90. Unfortunately , the NAUSET 16 was damaged during Hurricane Humberto--I am Bermuda based--when another boat broke free and took a large section out of the bow. There is quite a lot of damage to the NAUSET 16 along one of the chines where glass was worn out and separated from the foam, where the boat rode on a dock for a while during the storm while I bailed her out and then moved to a better location. (I will look for advice on repairs via a different thread as I do want to save her.} The Yamaha 90 engine escaped unscathed.

Since the storm, I have gotten my hands on a 1978 Montauk 17 hull in pristine shape. Part of the purchase deal was taking a Yamaha V4 130-HP two-stroke-power-cycle engine. I don't know the engine age, but this 130-HP is probably at least 8 to 10-years-old. It is not from the boat purchased, but as noted, was part of the purchase agreement. I reckon the 130-HP weighs 358-lbs, and let us assume it is in good shape for the sake of this discussion. (And it is in good shape in truth.)

I am in the camp of the Yamaha 90 being the perfect engine for Whaler 16/17 hull. I am inclined to move my Yamaha 90 to the new MONTAUK 17 boat which will become my main boat and then put the 130-HP on the repaired 1969 NAUSET 16 when it is back in the water.

Usage of my Boston Whaler boat s what I would call light-to-medium" : rarely pounding along in four-foot waves; more usually just inshore journeys in 0 to 15-knot winds and not much sea; rarely loaded with maximum number of people then driven hard; never taken way offshore here.

QUESTIONS

Q1: Is the 130-HP just out of the question too heavy for either the MONTAUK 17 or the NAUSET 16?
Q2: Is the 130-HP just not optimal, but would be fine if mounted on the MONTAUK 17 or NAUSET 16?

I keep fuel, battery and everything else out of stern and forward anyhow to balance the vessel. I am aware that the factory indicates 330-lbs Max but that they have seen up to 410-lbs but note it requires redistributing some weight to the bow.

Wwhen the Yamaha dealer mounted the 2018 90-HP on the 1960 NAUSET 16 in 2018, they had to mount the lower bolts into the engine well; they cut a 5-inch hole, dug out the foam back to the bolts, fastened them, then put an inspection cover over the opening. The dealer said the mounting holes had changed on the 2018 Yamaha 90 from the 2000 Yamaha 90 I had on previously

Q3: is [the mounting procedure used on to mount the 2018 Yamaha engine on the 1960 NAUSET 16 required] for a 1988 Montauk as well?

The mounting holes on the 1988 MONTAUK 17 boat are from a very old Evinrude 75-HP.

Q4: will the mounting holes from "a very old Evinrude 75-HP" match [the mounting holes on the bracket of a 2018] Yamaha 90?

I think someone out there will have knowledge about mounting holes.

When I get my hands on the 1988 hull I can check, but I am not getting it for a few more days.

Thanks in advance for any input on the engine weights and the mounting holes.

Soho

[jimh]

Q1: Is the 130-HP just out of the question too heavy for either the MONTAUK 17 or the NAUSET 16?

If your reckoning of 358-lbs for the weight of the 130-HP engine is accurate, I would hesitate to install it on the 1960 NAUSET 16 due to the boat's age of 59-years. The 41-year-old MONTAUK 17 is probably more suited for that engine weight. But both boats will be over-powered. Your initial comment that a Yamaha 90-HP is an optimum engine is a good assessment.

[jimh]

Q2: Is the 130-HP just not optimal, but would be fine if mounted on the MONTAUK 17 or NAUSET 16?

I do not think the 130-HP engine qualifies as "just fine" under any circumstance for the 1960 NAUSET 16. It is heavy and too much power.

The 130-HP engine (at 358-lbs) is heavier than optimum for the MONTAUK, but it may be workable. Many MONTAUK 17 boats have been re-powered with an E-TEC 90 that weighs 335-lbs without any reports of problems due to excessive engine weight. Often the boat battery is removed from the stern and relocated to the console to help eliminate weight.

[jimh]

Q3: is [the mounting procedure used on to mount the 2018 Yamaha 90-HP engine on the 1960 NAUSET 16 required] for a 1988 Montauk [17] as well?

The mounting holes on the 1988 MONTAUK 17 boat are from a very old Evinrude 75-HP.

First some background:

I suspect the problem the dealer encountered in mounting the 2018 Yamaha 90 was related to the removal of the optional blind-hole bosses on the engine mounting bracket.

Also, I suspect that the engine splash well on a 1988 MONTAUK 17 is probably deeper than the splash well on a 1960 NAUSET 16, so there may not be any problems related to the insufficient splash well depth that caused a mounting problem on the 1960 NAUSET 16.

For more information about problems in mounting modern engines to the transom of older Boston Whaler boats, see the answer to this FAQ:

Q8: How Does the Engine Mount to the Transom?
http://continuouswave.com/whaler/reference/FAQ/#Q8

The method you describe that was used by the dealer to install the 2018 Yamaha 90 onto the 1960 NAUSET 16 transom is one of the possible methods of accomplishing engine installation on Boston Whaler boats with shallow splash wells, but, as described in the FAQ answer, it is not the most expedient or preferred solution.

Now to answer your question: the mounting of a 2018 Yamaha 90 engine onto the transom of a 1988 MONTAUK 17 will not require the same procedure as the dealer used. I suggest you use the fifth alternative procedure as described in the FAQ answer linked above, considered the best alternative, is widely used, and is recommended by Boston Whaler in lieu of the method the Yamaha dealer employed.

[jimh]

I am aware that the factory indicates 330-lbs Max but that they have seen up to 410-lbs but note it requires redistributing some weight to the bow.

Where does the Boston Whaler company indicate those weights? I know they once published 410-lbs for a classic MONTAUK.

Q5: From where or from whom did you get the 330-lbs maximum engine weight specification?

[jimh]

Q4: will the mounting holes from "a very old Evinrude 75-HP" match [the mounting holes on the bracket of a 2018] Yamaha 90?

When outboard engine manufacturers adopted a standard transom mounting hole layout, the hole layout they adopted was already in use by OMC. This was codified as the B.I.A (Boating Industry of America) standard engine mounting hole location.

There is a high probability that the mounting holes on "a very old Evinrude 75-HP' will match the mounting holes on a 2018 Yamaha 90, since the old OMC layout and the B.I.A layout were the same and Yamaha is very likely using the B.I.A. layout. However, there is one important difference that is very likely to exist: the older OMC layout used a blind hole, a thread boss, in the engine mount. This blind hole is unlikely to exist on the 2018 Yamaha 90. If the mounting of your "very old Evinrude 75-HP" on one of the boats in this discussion made use of the blind hold, then that hole won't be useful with a 2018 Yamaha 90 engine.

Again, the FAQ gives an answer. See

Q9: What is the Standard Transom Hole Layout?
http://continuouswave.com/whaler/reference/FAQ/#Q9

[biggiefl]

To summarize:

Engine mounting is identical on older OMC and Yamaha engines to your 90hp today. The difference was many dealers used the blind holes as it was normal to have the engine mounted smack on the transom which has been proven to rob performance and hence why we mount higher today. A good installer would be familiar with the proper procedure to install but I have not seen and "smirked" hull needing an access plate.

The 130 Yamaha is the same weight ass a 115. It is VERY common for people to mount a 115hp or more on a classic 17. There is NO weight limits specified for a classic Montauk. I can promise that 358lbs is not too much weight compared to your current setup. The question is why? From what you state you do not have the need for a 50mph boat so why build one? Just because you have to buy the engine does not mean you have to use it. Is it even the correct shaft length? What is wrong with the older 75? They are very reliable engines and a good fit for the 16. With the price of fuel in Bermuda, why run a high HP 2 stroke engine? Sell it and buy something more suitable. Not sure when they stopped making the 130hp but it has been many years in the US. You guys have access to different engines due to emissions, etc.

Do you need 2 of the same type of boat? Would it be smarter to just sell everything as-is and enjoy your new Montauk?

[scottmcx]

I purchased my 1988 17ft Montauk new, with a 1989 Yamaha 2 stroke 130hp. As I recall the motor weighed in at about 400lbs. Perfect for the boat although not exactly legit as rated for 115hp (which weighed the same).
Still, have the same boat...1 repower to 130hp 4cyl ETC which also weighs in at about 400lbs.
Both push the boat to almost 60mph low load and 1 person with no exhaust chopper prop.
With a 3 blade 19in its a great 50+ MPH boat and will easily pull a 210lb slalom skier.
The ETEC is about 9 years old..considering the new 3cyl 150, at about 400lbs.
It should be a blast!

[Rick W]

"when the Yamaha dealer mounted the 2018 90-HP on the 1960 NAUSET 16 in 2018, they had to mount the lower bolts into the engine well; they cut a 5-inch hole, dug out the foam back to the bolts, fastened them, then put an inspection cover over the opening."

Oh no. I thought I was the only one with this installation nightmare