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Hello everyone, I am selling my Grady 225 and just picked up a 1985 Montauk 17 to use on the lakes, rivers and coast in SC. This one was owned by the SC Maritime Museum https://scmaritimemuseum.org/ and it has seen a lot of use but it is a solid little boat. I am thinking about re-powering with a Yamaha 4S either a 70 or a 90, any input on which engine? Here is a picture of my little diamond in the rough.
https://www.flickr.com/photos/1570000...ted-public After being a Grady guy for the past 10 years I am looking forward to being a Whaler guy now.

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I think that you will want the 90, as that is the recommended engine for the Montauk 17. That is a sweet little boat, you will love it. I have a 1994 Montauk 17 powered by a 2 stroke Yamaha 90 that I use down in Grand Isle, Louisiana and it handles anything that I want to be out in. Good luck.

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I agree that you will be happier with a 90HP. Look carefully at the weight of any prospective new engine. This hull was originally designed for a 2-stroke and the 4-strokes weigh a little more. My 1988 Montauk was re-motored with a 2004 Merc 4-stroke. It handles differently than when the original 2-stroke was on it. That said, the quietness of the 4-stroke is wonderful.

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There are not many days you can use the full power of a 90hp on a Lake or let alone even the Ocean due to chop, swells, etc.

Many people have a 70hp mounted on their Montauk
I have had 2 Montauks with a 70hp and skied behind them with a single ski.

I would look at the newer F70 4 Stoke due to the lighter weight and less expense of the 90hp.
http://www.whalercentral.com/articles...ticle_id=5

Compare 253 pounds of the F70 to the rest of the motors on the above list.
Nothing else compares.

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I talked to my Boat Shop and they recommended the 90 saying with 2 people the 70 would do alright but with 3 or 4 you need the 90. I like the weight of the F70 and the power of the 90. From what I can find the weight of the current 90 2S is about the same as the 70 4S. The problem the current 90 is 30 years old. The compression is 130,125,129 so I am going to run to for the time being.

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The first three things any new owner of a 1985 Boston Whaler Montauk 17 should do is:

1) Inspect the brass through hull fittings.
2) Learn how to replace the brass through hull fittings.
3) Replace and seal the new brass through hull fittings.

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I assume there might be an issue with the Brass Through Hull fittings?

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Yes, the neoprene o-rings used by Boston Whaler at the time your boat was manufactured deteriorated and, as a result, the waterproof seal was lost. The brass also deteriorates over time in salt water. For example, you could have what appears to be a good condition tube but 10 inches inward, at the center core of the transom and deep inside the urethane foam, you have a leak. Water seepage leads to saturation of the wood core and foam. The conventional wisdom here on this site is just replace old with new, that way you know you have good tubes with a tight seal using fresh caulk. See this article for background information for tips on how to replace and install new tubes. http://www.whalercentral.com/articles...icle_id=42

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I looked at your personal page photograph of your Montauk 17. I recommend you either modify your existing trailer to a bunk trailer with keel supports or buy yourself a new bunk trailer with the centerline keel supporting rollers. Read the owners manual for the Montauk 17 for further information about proper trailer set-up. Your trailer also looks too short.

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I talked to another shop, my Grady dealer and friend and he said most people do put the 70 on the Montauk 17 because of the weight. I watched several Youtube videos of a guy going from New England to Key West in a 1960s Montauk 17 with a Yamaha 70. Jury is still out.

https://www.youtube.com/watch?v=gffoU...ffoUc1RfoQ

https://www.youtube.com/watch?v=JDJKu...DJKuGdHDQg

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I would be cautious taking advice from dealers who sell outboards on what to repower a Montauk with. Each have an agenda.

All of the current 90hp four stroke and DFI engines available in the US are acceptable weight wise. The days of heavy 90hp 400+ lb motors are gone.

If your current motor has good compression, is up to date on maintenance and is relatively reliable, there is no sense to repower. It is an expensive undertaking (70hp ~9K, 90hp ~11K) and you will not get it back.

The classic Yamaha 70 and 90 two stroke motors are very good and age well if maintained.

Disclosure - I ran a classic Yamaha 90 2 stroke and an Yamaha F90 in the past.

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Well I have decided to go with a Yamaha F70. I am replacing the gas tank, fuel hose, filter, and the engine. My friend at Mid-Carolina Marine said the 70 works well if it is propped right. Anyone need a 1985 Yamaha 90 2S?

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There are several dozen owners who have repowered their Montauk's with an F70. It is a good selection.

Make sure the dealer mounts and props the engine correctly for a Boston Whaler.

There are guidelines with Whalers that are different than other hulls and you may need to push hard against a dealers contrary and uninformed advice.

The engine should be mounted at least 2 holes up, possibly 3 depending on prop. (2 empty holes above the top bolts. Bolt in third hole counting down from top)

Here are recommendations from Montauk owners who have repowered with the F70 and tested many props. Note size/performance is not universal so make, model and pitch must be followed.

13 x 17 Yamaha Painted SS
13.25 x 14 Yamaha Performance Series
13.25 x 14 PowerTech SCP (3 holes up)

When they test the prop, the boat should reach 6100-6300 rpm's at WOT and a speed of 35+ mph with a light load. The WOT for this engine (6300) is higher than others.

Propping the boat is not all about going fast. It is important to prop the boat right so the engine performs correctly at all speeds.

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Well I have confidence in my dealer, the owner and I are in the same Sunday School class and I have dealt with them since 1992. They also sold and rigged Whalers before Brunswick bought them. I trust them.

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Do NOT let them mount the new motor all the way down.

That is how it was done years ago with old motors and props.
Do not let them do that as old habits die hard and it will not be done properly for today's motors and props.

As Phill mentions, 2 holes up.
http://www.whalercentral.com/articles...cle_id=106

See how new lower holes will probably need to be drilled on your transom.
http://www.whalercentral.com/infusion...ser_id=291
http://www.whalercentral.com/articles...icle_id=82

For your 1985 17' hull, you will probably need the lower Green holes drilled.

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Greetings from Columbia. How many hours are on your 2-stroke? I've got the same boat/motor combo, just 2 years newer. I'd have told you "just keep the old motor" as they're pretty tough to kill but there are times I'd like the quiet of a 4-stroke.

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I have a lot of experience with Montauks and 70hp 4S vs 90 Yamaha 2S. My Montauk ran 41.5 w/ the 90 which we all agree performs more like 80+hp compared to an OMC 90 4cyl. With the 70 Suzuki on a manual jackplate she would go 39.5. My bud Len put a 90 E-Tec on his Montauk with a Jackplate and he only fetched about the same as a 90 Yamaha 2s. I have also heard they are a tad weak on making 90hp as well. My Suzuki with jackplate and prop was about 400lb and I had no issues with the weight. I would repower with that setup all day long. Now....I have been reading up on repowers and I noticed that the new F70 on classic 15's is not performing like the OMC 70 2 strokes by a good margin. Most are getting low 40's compared to what should be 45/46. I hope the new F70 is a real 70hp unlike the 90 2S. I also assume many people do not experiment with height and props like I do. I probably tried 6 props on my boat before I found the right one. I tried 3 OMC SST props and got 3 different results(OMC & Suzuki pros interchange just like Yamaha & Merc).

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I honestly do not know the number of hours. I just purchased this rig and it came from the Maritime Museum in Georgetown. Just like a rental car, no one really cares about a company car or boat. It does have good compression so I am told and there is a lot of rust, the lower unit has been replaced with another one. It runs OK, a little rough at lower speeds and smooth running fast. The dealer had to do a lot of work to get the steering to move, it was frozen. I use it on Lake Greenwood and I want to take it down to Murrells and Georgetown ie Black and Pee Dee rivers and go exploring. Good to hear from a fellow Sandlapper.

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Good info but since I have not got the engine yet I can't comment on the performance but I will certainly keep everyone informed.

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Just saw your photo on your personal page... I actually looked at your boat (for fun) when it was out in front of the Boat Shed. Other than Lake Greenwood, I've been everywhere you've mentioned in my Montauk. It's the perfect river boat (my avatar is from Sandy Island). Only suggestion I have is look into a stern seat.
It's worth it. Enjoy!