Outboard swap, transom profile, bracket shape

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Author Topic:   Outboard swap, transom profile, bracket shape

DanT posted 11-27-2001 06:19 PM ET (US)
I have a 1966 Eastport. Time has come to retire the original 1966 100hp Evinrude. I found a used 90hp Yamaha that I would like to use. The transom has a slight curve to it. The old Evinrude had a two piece bracket that bolted tightly to the transom. The Yamaha bracket is one piece and flat. I haven't put the Yamaha on the boat yet but I think the bracket won't lay flat against the transon due to the slight curvature of the transom. The mounting holes should line up but I am concerned about the correct way to attach the bracket. Should a shim of some sort be used? Also, does anyone know the thread size of the blind mounting holes on the Yamaha? Thanks Dan

Wayneman posted 11-27-2001 07:21 PM ET (US)
Hello DanT,

What are you going to do with your old Evinrude 100? Is it worth rebuilding? I might be interested.
Bigshot posted 11-28-2001 09:58 AM ET (US)
What blind mounting holes?
DanT posted 11-28-2001 03:46 PM ET (US)
Bigshot,
The blind holes (I think that's what they are called) are the lower holes in the Yamaha bracket that will match up with the lower holes in the splash well. They are threaded but dont pass all the way through the bracket. The bolt would be inserted from the splash well and threaded into the bracket. This hole is not visible from outside. Thanks, Dan
DanT posted 11-28-2001 03:56 PM ET (US)
Wayneman,
I haven't decided what I'm going to do with the old Evinrude. It does run but it needs some maintenance. If you're interested and would like to make an offer I'll consider it. If you want more information on the motor send me an Email. Dan
Bigshot posted 11-28-2001 04:20 PM ET (US)
Mine has a slot that the bolt goes through. When you look at the back of my 90 Yamaha you see 4 bolts. All engines are that way. Double check. That blind thing is for something else I believe.
DanT posted 11-28-2001 05:12 PM ET (US)
I checked the motor and transom again. The bracket has four holes near the top, one blind hole and then a slot below the blind hole. The hole pattern in the transom from the old Evinrude matches perfectly with the top two holes and the blind holes. If I were to use the slots they will fall below the splash well and a lag screw would be needed. If the motor was raised to allow access to the slots from the splash well I would still need to redrill the transom because the distanse between the slots is less than the distance between the blind holes. What I'm really interested in is how to deal with the slight curvature of the transom when using a bracket that is straight. Dan
Clark Roberts posted 11-28-2001 05:41 PM ET (US)
Some of the early Montauks had very shallow splash wells and it was not possible to use the two lower bolt holes (or lower slots) and the blind (threaded) holes were necessary. Most engines have these blind holes... great if you need them but there is no height adjustment once transom is drilled! Clark
Bigshot posted 11-29-2001 10:39 AM ET (US)
Learn something new everyday!
gunnelgrabber posted 11-29-2001 04:17 PM ET (US)
it's mostly an omc "thing" , maybe? when i got my old used katama it was "one hole up",blind holes drilled for it.i thought the engine ,( for different reasons) was supposed to have the cav plate flush with boat bottom.so i lowered it one hole (all the way down)...after reading clark and others recommending "go at least one hole up"..i returned.. and as clark just said...2 pr. of blind holes now.filled the extras. wow! does it go good! and feels like power steering!haven't checked gps yet ,but the seat of the pants perception is a significant difference!! learned it all right here. thanks..lm

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Author	Topic: Outboard swap, transom profile, bracket shape
DanT	posted 11-27-2001 06:19 PM ET (US) I have a 1966 Eastport. Time has come to retire the original 1966 100hp Evinrude. I found a used 90hp Yamaha that I would like to use. The transom has a slight curve to it. The old Evinrude had a two piece bracket that bolted tightly to the transom. The Yamaha bracket is one piece and flat. I haven't put the Yamaha on the boat yet but I think the bracket won't lay flat against the transon due to the slight curvature of the transom. The mounting holes should line up but I am concerned about the correct way to attach the bracket. Should a shim of some sort be used? Also, does anyone know the thread size of the blind mounting holes on the Yamaha? Thanks Dan
Wayneman	posted 11-27-2001 07:21 PM ET (US) Hello DanT, What are you going to do with your old Evinrude 100? Is it worth rebuilding? I might be interested.
Bigshot	posted 11-28-2001 09:58 AM ET (US) What blind mounting holes?
DanT	posted 11-28-2001 03:46 PM ET (US) Bigshot, The blind holes (I think that's what they are called) are the lower holes in the Yamaha bracket that will match up with the lower holes in the splash well. They are threaded but dont pass all the way through the bracket. The bolt would be inserted from the splash well and threaded into the bracket. This hole is not visible from outside. Thanks, Dan
DanT	posted 11-28-2001 03:56 PM ET (US) Wayneman, I haven't decided what I'm going to do with the old Evinrude. It does run but it needs some maintenance. If you're interested and would like to make an offer I'll consider it. If you want more information on the motor send me an Email. Dan
Bigshot	posted 11-28-2001 04:20 PM ET (US) Mine has a slot that the bolt goes through. When you look at the back of my 90 Yamaha you see 4 bolts. All engines are that way. Double check. That blind thing is for something else I believe.
DanT	posted 11-28-2001 05:12 PM ET (US) I checked the motor and transom again. The bracket has four holes near the top, one blind hole and then a slot below the blind hole. The hole pattern in the transom from the old Evinrude matches perfectly with the top two holes and the blind holes. If I were to use the slots they will fall below the splash well and a lag screw would be needed. If the motor was raised to allow access to the slots from the splash well I would still need to redrill the transom because the distanse between the slots is less than the distance between the blind holes. What I'm really interested in is how to deal with the slight curvature of the transom when using a bracket that is straight. Dan
Clark Roberts	posted 11-28-2001 05:41 PM ET (US) Some of the early Montauks had very shallow splash wells and it was not possible to use the two lower bolt holes (or lower slots) and the blind (threaded) holes were necessary. Most engines have these blind holes... great if you need them but there is no height adjustment once transom is drilled! Clark
Bigshot	posted 11-29-2001 10:39 AM ET (US) Learn something new everyday!
gunnelgrabber	posted 11-29-2001 04:17 PM ET (US) it's mostly an omc "thing" , maybe? when i got my old used katama it was "one hole up",blind holes drilled for it.i thought the engine ,( for different reasons) was supposed to have the cav plate flush with boat bottom.so i lowered it one hole (all the way down)...after reading clark and others recommending "go at least one hole up"..i returned.. and as clark just said...2 pr. of blind holes now.filled the extras. wow! does it go good! and feels like power steering!haven't checked gps yet ,but the seat of the pants perception is a significant difference!! learned it all right here. thanks..lm