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Author Topic:   MONTAUK: Re-Power with Yamaha 90

Azwhaler posted 09-13-2007 02:15 PM ET (US)
Have a 79 Montauk with 98 Merc 100 2s.. Considering a swap to 2 stroke Yamaha 90. Trying to reduce weight (350# now) and all the 4 strokes above 60 hp are too heavy and don't feel my Montauk with heavy add ons will perform well with Merc 60 4 stroke. question..will Yamaha mounting holes line up? What other changes or problems would I encounter, cables, controls gauges etc???
Everyone I have talked to with the 90 Yamaha are very satisfied and the weight I feel is right for this boat.
Thanks.
Tohsgib posted 09-13-2007 02:30 PM ET (US)
Bolt holes will line up but 350lbs is not heavy. Nor will shaving 80lbs and 1 cyl going to help with anything but MPG. The 90 Yamaha 2s is more like 80hp but is much less thirsty than that big 100 Merc.
Tohsgib posted 09-13-2007 02:31 PM ET (US)
Controls will work but wiring harness, gauges(maybe), cables, etc will all have to be changed over to Yamaha which is EXPENSIVE. prop might be able to swap but the 90 will use a 13x17 and OEM Yamaha works the best on them.
Peter posted 09-14-2007 07:39 AM ET (US)
Actually, the 13 x 19 aluminum Yamaha propeller works well for a Yamaha 90 on a 17 Montauk. If you are pulling skiiers or water toys, then dropping down to a 13 x 17 wouldn't be a bad idea. Although the Yamaha 90 may not be the strongest 90 HP motor ever offered, its light weight makes it a great match for the Montauk and its got enough get up 'n go to satisfy most users.
Of course you will have to swap out the wiring harness and gauges but I would also switch over to the Yamaha controls and cables.
Tohsgib posted 09-14-2007 11:26 AM ET (US)
My 90 ran 5500 with a 13x17 so I guess a 13x19 and 5100 would be fine but he is running heavy loads from what I gather. I still think he should just stick with the Merc unless he needs to repower or just hates the engine.
Mobjack posted 09-14-2007 01:58 PM ET (US)
I too am going to jump on this one, having considered the 2stroke yamaha 90 as a repower option for my montauk. Will the bolt holes line up with the already existing holes for my 1985 johnson 75 horse? anybody know?
Tohsgib posted 09-14-2007 02:27 PM ET (US)
Yes as long as yours was not in the blind holes.
Azwhaler posted 09-14-2007 03:20 PM ET (US)
Thanks for the info. My concern about weight is based on my experience of driving this Montauk for 20 years with a 288# in line Merc 90. Ocean and large lakes. Have a heavy teak seat, aux fuel tank and small kicker in the back... With heavier motor it was sluggish and dug in too much and wallowed in turns and with the shallow splash in the 79 models, a noticeable increase in water over the back with following seas or backing up against waves. Everyone who was familiar with it and rode or drove boat commented on it right away also. My motivation now is that I am not sure how much longer the older 2 stroke design Yamaha will be available. I have driven several Montauks with this motor recently and really liked the handling and power.

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Author	Topic: MONTAUK: Re-Power with Yamaha 90
Azwhaler	posted 09-13-2007 02:15 PM ET (US) Have a 79 Montauk with 98 Merc 100 2s.. Considering a swap to 2 stroke Yamaha 90. Trying to reduce weight (350# now) and all the 4 strokes above 60 hp are too heavy and don't feel my Montauk with heavy add ons will perform well with Merc 60 4 stroke. question..will Yamaha mounting holes line up? What other changes or problems would I encounter, cables, controls gauges etc??? Everyone I have talked to with the 90 Yamaha are very satisfied and the weight I feel is right for this boat. Thanks.
Tohsgib	posted 09-13-2007 02:30 PM ET (US) Bolt holes will line up but 350lbs is not heavy. Nor will shaving 80lbs and 1 cyl going to help with anything but MPG. The 90 Yamaha 2s is more like 80hp but is much less thirsty than that big 100 Merc.
Tohsgib	posted 09-13-2007 02:31 PM ET (US) Controls will work but wiring harness, gauges(maybe), cables, etc will all have to be changed over to Yamaha which is EXPENSIVE. prop might be able to swap but the 90 will use a 13x17 and OEM Yamaha works the best on them.
Peter	posted 09-14-2007 07:39 AM ET (US) Actually, the 13 x 19 aluminum Yamaha propeller works well for a Yamaha 90 on a 17 Montauk. If you are pulling skiiers or water toys, then dropping down to a 13 x 17 wouldn't be a bad idea. Although the Yamaha 90 may not be the strongest 90 HP motor ever offered, its light weight makes it a great match for the Montauk and its got enough get up 'n go to satisfy most users. Of course you will have to swap out the wiring harness and gauges but I would also switch over to the Yamaha controls and cables.
Tohsgib	posted 09-14-2007 11:26 AM ET (US) My 90 ran 5500 with a 13x17 so I guess a 13x19 and 5100 would be fine but he is running heavy loads from what I gather. I still think he should just stick with the Merc unless he needs to repower or just hates the engine.
Mobjack	posted 09-14-2007 01:58 PM ET (US) I too am going to jump on this one, having considered the 2stroke yamaha 90 as a repower option for my montauk. Will the bolt holes line up with the already existing holes for my 1985 johnson 75 horse? anybody know?
Tohsgib	posted 09-14-2007 02:27 PM ET (US) Yes as long as yours was not in the blind holes.
Azwhaler	posted 09-14-2007 03:20 PM ET (US) Thanks for the info. My concern about weight is based on my experience of driving this Montauk for 20 years with a 288# in line Merc 90. Ocean and large lakes. Have a heavy teak seat, aux fuel tank and small kicker in the back... With heavier motor it was sluggish and dug in too much and wallowed in turns and with the shallow splash in the 79 models, a noticeable increase in water over the back with following seas or backing up against waves. Everyone who was familiar with it and rode or drove boat commented on it right away also. My motivation now is that I am not sure how much longer the older 2 stroke design Yamaha will be available. I have driven several Montauks with this motor recently and really liked the handling and power.