1977 MONTAUK Transom Strength

[Montoxication]

Q1: will a [1977—always use four digits for year designation] MONTAUK 17 transom support a hydraulic jack plate, like the one linked below?

https://bobsmachine.com/product/4-setba ... ate-300hp/

Q2: will [the transom] support a PowePole?

Q3: will [the transom support a Yamaha] 115 VMAX SHO engine?

Q4: will the transom of a 1977 MONTAUK 17 support all three: the engine, the jack plate, and the PowerPole?

[Phil T]

Even with moving the battery to the console, the hull will have a significant stern bias at rest and coming off plane may ship water over the transom.

I recommend you add the necessary weight to the transom to simulate the proposed weight of the new engine, jack plate and power pole. Drive around, come off plane, see for yourself.

Note - Only add the minimum setback necessary (4"). The hull will porpoise more frequently with the added weight on the transom, added setback will increase it exponentially.

Report back your observations.

[jimh]

Your questions essentially resolve to this:

Q4: will the transom in a particular 46-year-old 17-foot Boston Whaler hull be so strong it can safely support adding an engine that exceeds the maximum power rating and is likely much heavier than engines in use at the time the boat was designed, while at the same time adding even more load on the transom with a electrically operated jack plate, and then even more load with an electrically operated PowerPole anchor?

Each of your proposed modifications adds considerable weight at the transom. Taken together, the added weight will be almost certain to put the engine splash well drains below the static waterline, which is a good indicator that there is too much weight on the transom.

Further, the transom may already be compromised by intrusion of water into the embedded wood causing rot. Even if the boat and transom were new, the proposed amount of weight would likely exceed the designer’s intentions for this hull.

Of course, it is YOUR hull and you’ll be the person using the boat, so there is nothing stopping you from making these modifications. But it sounds to me that you should be getting a bass boat or an all-species boat for anglers designed to have all the components you want to add already included as part of its design, rather than an open lightweight center console skiff that is 47-years-old.

[Dsmith181]

I was wondering the same thing. I have a 1978 Montauk [17]. I plan to put on a Mercury 115-HP FOURSTROKE instead of the MARINER 115-HP engine I have on there currently.

Q5: Should I reduce engine power to 90-HP because of the weight?

Q6: What is the biggest four-stroke-power-cycle engine recommended?

To go fast is fun, but not at the expense of damaging the transom.

[Phil T]

Determine the weight differential between the current engine and the 115 hp motor and add it to the stern. Drive the boat around.

While I doubt [a Mercury 115 FOURSTROKE engine weight of 360-lbs] will be a problem; many owners installed Honda BF90 engines in the 2000's that weighed 379-lbs.

[Phil T]

The hull is rated for 100hp. There was no weight limit standard in 1978.

[rbbiggs]

Q6: What is the biggest four-stroke-power-cycle engine recommended?

[Recommends a] Suzuki DF90A [on the basis that it will be] quiet, light weight, [and produce] great [fuel economy].

[jimh]

Note that this thread was discussing the strength of the transom on an older MONTAUK boat. There has been a new topic introduced regarding the fuel efficiency of two SUZUKI engines. That topic has been moved to its own thread in the PERFORMANCE forum. Please see

Fuel Efficiency of Two Suzuki Engines
https://continuouswave.com/forum/viewto ... f=7&t=8181

Also note that the originator of this thread has not replied to any comments made in reply to his several questions for over nine months. On that basis, the thread is now closed to further comments.