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I have a 1982 Montauk 17 that I need to repower. I found a very good deal on a new Yamaha 90Hp four stroke. I am concerned about weight. I believe it weighs 366lbs. The motor that was on it was the original Johnson 2 stroke 90Hp. That motor weighs 300lbs. There has always been a 7.5 Hp Johnson kicker also on the transom which ways about 55 or 60 lbs. So I feel that it's not going to be that much difference. I would appreciate any thoughts on this. To me having that brand new Yamaha 90 four stroke will be amazing. I just hope not to heavy. Thank you for any insight. Pics below.

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The boat can handle the weight. For several years, Whaler factory installed the Mercury 4-stroke 90, with Yamaha powerhead, on Montauks, which weighed 388lb at the time.

I was also recently looking at pricing on a new 2017 Mercury 4-stroke 90, with large 2.0 liter displacement and 359#, and was quoted $6825, including a 5 year warranty. That also seemed like a good deal. This is the same engine Whaler is now furnishing as standard equipment on the 170 Montauks.

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I have a 100hp Yamaha 4 stroke albeit year 2000 & it weighs 356 on a 1999 montauk (same hull as yours), no issues. Top speed is 45 for me.

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A 90 hp Yamaha should be a good engine for that boat. I have a 1977 Montauk and it has an Etec 75 which weighs about 320 and weight is no issue at all.

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Too heavy.

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I have a F90 on my 1984 Montauk and it has been great. I have tried kicker motors on it: F6, F9.9, and F15. If you are going with an engine this heavy, I would first suggest making sure that you have moved your battery(s) to the console for better weight distribution. I think that for 2005, the motor weighed in at 369 pounds. It's a little heavy but it works great. When you start adding a kicker, things get a little dicey. The F15 was much to heavy at 120 pounds - the boat listed to starboard and would have water splash over the transom pretty easily. The F6 is the best option: it can get you about 5.5 mph and it only weighs 60lbs. But in the end, I decided not use the kicker on the boat at all. I bought the reliable F90 and run with it. There really isn't much to be gained by having the kicker there. It's not going to save you much money in fuel costs and the F90 is amazingly fuel efficient and reliable. Just maintain the F90 and it should treat you well. Actually the new F115 weighs in at 377 now - I might get that instead.

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I went through this dilemma a couple years back. Personally I thought that the F90 was too heavy. If I recall, that was the consensus I got from fellow members here at the time, and it was consistent with what the Yamaha sales rep was telling me. He suggested the F70, even though he would have made more $ on the 90. BTW, he was actually a Whaler dealer and Mercury was an option, but he still thought the F70 was the way to go. My hull is a 1998 - don't know if that makes a difference. School of thought was that with the F70 coming in at 100 lbs lighter than the 90, whatever advantage you get from the extra hp will be kinda small. Maybe a few more mph, but with a few less mpg to go along with it. I' ve certainly seen 90s on the back, and IMO it looks low to the water, and if you are going to ad anything else to the stern it will look lower. Like you, I originally had the 90 hp Johnson Oceanrunner (pro?). I'm on the bay, and on flat water and with good trim I get to high 30s mph. Just a thought. Best of luck.

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I put a Yamaha 90 4 stroke on my 1979 Montauk back in 2005. Could not be happier. Moved the battery to the console. It gets 5-6 miles per gallon. A big difference you may want to look at is Alternator output. The New 90's have 35 amps, the 70's only 17 amps.
If you have chart plotters, depth finders, radios etc, 35 is better than 17.
Yes it sits a little lower in the water, but I never worry about the battery going dead. If I need to replace my motor, a 90 is what I will replace it with. The 75 and 90 weigh the same, only the 70 is lighter but less amps.

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nyc511 Did you install the Yamaha F70 in your boat? (Your comments imply that you did, just want to verify.) If so, would you make the same decision again? I'm torn between the (heavy) F90 at 366# and the F70 (at 257#). I don't need a super fast boat (mid 30s would be fine) but would like to get a moderately heavy load on plane reasonably quickly. Does the 70 do that?

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Check out previous threads under "engines" to find discussions regarding repowering 16/17 hulls - tons of good info.

Per this link below, I think the new 2017 Yamaha F90 weighs in at 353lbs - because it says the new model is 13lbs lighter than the previous model (which was 366lbs). I have not yet heard a report on this 2017 motor on a 16/17 hull, but it should be good.

http://2017newproducts.yamahaoutboards.com/

From my experience, the F70 at 257lbs is a great match for the 16/17 hull. The power / weight ratio is a nice balance, it sips fuel, it's very quiet, reliable and very quick & responsive. I moved the batt under the console as well.

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I would go with the lighter F70. Stern heavy boats tend to drag a big wake behind them when they are off plane, which for most operators is how the majority of time aboard is spent (especially if you fish.).

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With boats this old you need to see how your boat sits in the water. It just might be wrong to hang nearly 400 pounds off the back.

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So just to reply to everyone who responded to my question. Thank you all so much for your input. This was a tough decision but I decided to go with the ETEC 90HP. Reasons being, the weight is almost 50LBS lighter, I got a great deal on this brand new 2017 model with controls which saved me over two thousand bucks! The torque on this thing is incredible, fuel economy is better, no maintenance for three years or 300hrs! It has the lowest emissions of any motor on the water and its really fast. I'm still experimenting to determine if they gave me the right prop. I'm able to get it to about 4500 RPM's and getting up to 34MPH. With this added torque I am now having a problem with the boat listing to port when on plane, so I'm looking for a remedy there. Working the trim does help some but not completely. Has anyone experienced this with their Montauk 17? Should I install trim tabs? Thanks again!

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See other thread on trim changes.

What is the prop the dealer provided. Note there is no "standard" prop.

Make, model and size (x" by y")

You should be hitting 43-46 running solo if rigged and propped right.

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I'm sure you'll get some additional input on this; I'm guessing that the engine was installed "all the way down" on the transom base on your description of yawing / torque roll. Having too much of the lower unit in the water at speed will increase drag and can cause this effect. The diameter and pitch should be stamped on the propeller hub, let us know what information is on there. Your RPM readings are WAY below what Evinrude recommends for the engine, the propeller on the boat may have too much pitch and will cause damage to the engine if you run it under these conditions over the long term. I'm guessing by the numbers that you have at least a 19" pitch, maybe even a 21".

I have the 2012 version of the 90 HP E Tec on my 1989 Montauk 17 with a 14.25" x 15" pitch Stiletto Advantage stainless propeller, engine is mounted "two holes up" on the transom and will turn 6,200 RPM / 43 mph on GPS with just myself on board. The Stiletto propellers have been discontinued although they sometimes are available used. If I remember correctly, another choice that was recommended when I was repowering was the Evinrude "Viper" stainless propeller, 17 inch pitch. (The Stiletto propeller I have acts like a 17" pitch even though they called it a 15") There's a ton of information on here about propellers, transom mounting height, etc., do a search and you should find the answers you need. Good luck and keep us posted.

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I have a 1980 Montauk and it has a 2015 Evinrude E-tec 90hp on it , works great and top speed is around 38 mph