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1982 17' Montauk with 75 HP Two Stroke Merc
garym	#1  Posted on 10/18/16 - 5:20 PM
Member Posts: 6 Comments: 0 Joined: 10/17/16	Anyone have any experience with re powering a 17' Montauk with a Four Stroke 90 HP Yamaha (366 lbs). The shaft length is 25" but I would put a riser on the transom to correct this. The current 75 HP Merc (1994) has 20" shaft length and is 300 lbs. Thanks for your help. Gary
Sharky1	#2  Posted on 10/18/16 - 5:38 PM
Member Personal Page Posts: 30 Comments: 3 Joined: 03/29/10	Hummm, I don't think I really know what you're saying. All Montauks require 20" shafts. So what I think you're saying is what would happen or if it's ok to do it? I think that's a lot of pressure on the block and I wouldn't recommend it. I haven't ever heard of anyone doing it but you never know, you may be the first.
Joe Kriz	#3  Posted on 10/18/16 - 5:42 PM
Site Owner Personal Page Personal Album Photo Albums Project Albums Posts: 11447 Comments: 452 Joined: 03/18/05	The F90 weighs 372 pounds for a 25 inch shaft model. The 20 inch shaft model weighs in at 366 pounds. http://yamahaoutboards.com/outboards/...ifications I would rethink trying to adapt a motor that is too long for the transom and adding any extra weight as that 90 isn't light to begin with. Much better off with the F70 at 257 pounds. There aren't that many smooth water days to open up a 90. At least from my past experiences. The lighter the weight the better. http://www.whalercentral.com/articles...ticle_id=5
garym	#4  Posted on 10/18/16 - 5:52 PM
Member Posts: 6 Comments: 0 Joined: 10/17/16	There is also a Yamaha 75ph with the same block but a 20" shaft available. The weight is probably similar. How about the performance compared to the ole 2 stroke 75
Joe Kriz	#5  Posted on 10/18/16 - 5:56 PM
Site Owner Personal Page Personal Album Photo Albums Project Albums Posts: 11447 Comments: 452 Joined: 03/18/05	The weight of the F75 and the F90 are exactly the same for a 20 inch shaft version. 366 pounds each. You would be better off with the F90 if power is what your after without adding anymore weight over the F75.
garym	#6  Posted on 10/18/16 - 6:04 PM
Member Posts: 6 Comments: 0 Joined: 10/17/16	Unfortunately the 90's are all 25" and the 75" are 20". What about performance with the heavier 4 stroke vs 2 stroke. I know that the starting is slower with the 4 stroke and the torque is higher but I haven't have anyone reply directly with "the 4 stroke performs better than the 2 stroke" or "the 2 stroke is a better engine than the 4 stroke, for this Whaler"
Joe Kriz	#7  Posted on 10/18/16 - 6:33 PM
Site Owner Personal Page Personal Album Photo Albums Project Albums Posts: 11447 Comments: 452 Joined: 03/18/05	garym wrote: Unfortunately the 90's are all 25" Where are you getting that info? Or is that all your local shop is trying to sell you? If you can't buy a 20 inch in Canada, then try the U.S. The Yamaha website clearly shows both the 20 inch and 25 inch is available for the F90 model. See the link I gave you above again.
garym	#8  Posted on 10/18/16 - 6:40 PM
Member Posts: 6 Comments: 0 Joined: 10/17/16	There are some "camp" boats just returned, still under warranty but they only have 90's with the 25" shaft. The 75's are 20". I'm still looking for input on performance of a 2 stroke vs 4 stroke on these older 17's
Sharky1	#9  Posted on 10/19/16 - 10:21 AM
Member Personal Page Posts: 30 Comments: 3 Joined: 03/29/10	I have a Suzuki 90hp 4stroke on my 17 and I wouldn't trade it for anything. Top speed is about 43mph but the most impressive thing is the fuel consumption. It's rediculous how economical it is cruising at about 18mph. Never again will I put a 2stroke on any of my boats. Money wise Suzuki is much cheaper than Yamaha but you have to make sure there is a Suzuki dealer in your area. When I switched over to 4 stroke I gained another 100lbs which is very substantial. The only time it really makes a difference is when I'm climbing up the dive latter. Overall the performance, efficiency, and quietness is remarkable.
garym	#10  Posted on 10/19/16 - 10:43 AM
Member Posts: 6 Comments: 0 Joined: 10/17/16	Hi Sharky, that's the feedback I'm looking for. The Yamaha 75 or 90 is about 100lbs heavier. I am looking at a used engine with a warranty still on it so the price is reasonable. The 90 has a 25" shaft instead of a 20" so will have to put a 5" riser on the transom. The Yamamha dealer says he does it all the time and it works well and doesn't hurt performance - any comment? Thanks
alan heckmamleper	#11  Posted on 10/19/16 - 12:13 PM
Member Posts: 79 Comments: 0 Joined: 04/14/13	I have a 1999 Alert 17, it used to have a 2005 Mercury 2 stroke 75 hp and I got 38 mph for my top speed. I repowered with a Yamaha F70 and with 2 people and 20 gallons of gas plus fishing equipment top speed is 36.4 mph. Lightly loaded with just me I get another 1 to 1.5 mph. The 360 lb motor will make your boat handle sluggish and ride hard and get ready to take some waves over the transom. The Yamaha F70 is a great fit for a Montauk 17, it's light weight (257 lb) is a big plus as I have found out from experience and fuel economy can not be beat. My motor is mounted all the way up with a Yamaha Performance Series SS 13.25 x 14 prop. The ride is smooth and it handles like a sports car. I agree with Joe, how many days can you go faster than 35 mph. Yamaha F70 is a great fit, Joe is right.
ursaminor	#12  Posted on 10/19/16 - 7:31 PM
Member Personal Page Posts: 67 Comments: 0 Joined: 08/12/12	A 25" shaft on a 20" transom just because it's a "camp boat" deal is not a good choice. You'll end with up with something worth less combined than what you have now. If this is the best deal you can afford, go with the 20 inch / 75 HP Yamaha. There are other lighter and better choices, the 70 HP Yamaha F70 is one, the 75 / 90 HP Evinrude is another. Transom weight is important on these boats, the closer to 300 lbs (or less) you can get, the better the boat will perform. I love the speed of the 90 on my boat but agree that we spend much more time cruising than blasting at full throttle. 75 HP is plenty on a 17 Montauk on any given day. 1989 Montauk 17 / 2012 90 HP Evinrude E-TEC
garym	#13  Posted on 10/19/16 - 9:28 PM
Member Posts: 6 Comments: 0 Joined: 10/17/16	Thanks for the advise
Phil T	#14  Posted on 10/20/16 - 5:28 AM
Administrator Personal Page Personal Album Project Albums Posts: 7043 Comments: 6 Joined: 03/26/05	Gary - Raising the transom can be very expensive. A more economical solution that will not alter the transom is installing a jack plate. Note: You want the lowest amount of setback possible. Setback increases the hull's tendency to porpoise. See http://www.bobsmachine.com/Standard-M...gn_c17.htm http://www.cmcmarineproducts.com/prod...ack-Plates