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Author Topic:   Mounting my Yamaha to my Nauset-Help
kentupps posted 06-07-2003 12:36 PM ET (US)   Profile for kentupps   Send Email to kentupps  
I have a 90HP 4 stroke and I am trying to mount it to my 1967 17' Nauset. The mounting holes on the Yamaha do not fit ont the boat because of the high splashwell. What mounting bracket and/or jackplate systems will work.
I bought a Detwiller jackplate on Ebay and this does NOT fit properly, (the steering arm on the engine interfears with the jackplate operation).
Montauk posted 06-07-2003 12:55 PM ET (US)     Profile for Montauk  Send Email to Montauk     
You have to mount to the blind holes on the engine mount. The other way is mount the engine up on the transom which is where it should be.
JBCornwell posted 06-07-2003 03:04 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
You have mail, Ken.

Red sky at night. . .

Hobie1981 posted 06-07-2003 09:15 PM ET (US)     Profile for Hobie1981  Send Email to Hobie1981     
Ken: You'll have to use Yamaha's mounting bolts for the blind holes. I believe its a M12 Fine thread. Nobody makes them in SS/ fine thread. I believe I paid 5.00 each for the bolts at the local Yamaha dealer.

I just repowered my '69 Nauset with a nice 1988 70 HP Yamaha 2S. 38-39 MPH by my GPS. No need to go any faster, must have loosened every filling in my mouth. Gotta love the smurfless hull. :-)


Hobie1981 posted 06-08-2003 10:05 AM ET (US)     Profile for Hobie1981  Send Email to Hobie1981     
Make that "smirkless"
jimh posted 06-08-2003 11:09 AM ET (US)     Profile for jimh  Send Email to jimh     
This is a common problem in mounting modern outboard motors to these older hulls.

I wish someone who has good knowledge about this and perhaps some photographs on various installations would take the time to write up an article about it.

I would be very pleased to publish in the Reference section, perhaps as part of the FAQ, any article that answered this in detail.

I don't have any experience myself on this topic, nor do I have access to an older hull to take pictures, etc.

If anyone has solved this problem I would welcome contribution of that information to a permanent article that people could be referred to.

roccus posted 06-09-2003 09:01 AM ET (US)     Profile for roccus  Send Email to roccus     

I've got a similar problem to Kentupps. Trying to mount a 90 hp Yamaha 2-stroke to a Nauset, without lagging bottom two bolts. Frustrating.

Tried to use a manual jackplate to utilize four upper holes in transom, but the cowling won't clear the transom when tilted up fully. Can't raise the engine any higher without effecting ventilation plate position along keel line.

I'm not fimilar with the "blind holes" referrred to. Are they in the mounting bracket? Does that mean the bolt travels from the inner skin of transom and out into the outboard?


Hobie1981 posted 06-09-2003 10:12 AM ET (US)     Profile for Hobie1981  Send Email to Hobie1981     
Hi Guys: The Yamaha p/n for the bolt(s) is 90101-12M65. You'll need 2. :-)

Blind hole(s) is in the mounting bracket about midway.

Bolt head will be on the inside of your transom.


Bigshot posted 06-09-2003 11:51 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Ok the last post id puzzling from roccus. when using a jackplate the purpose is for the AV plate to be able to be raised higher than the keel.....the only reason for a jackplate. You should have the engine jacked about 4" higher than the transom making the Av plate about 3" above the keel....maybe more.
lhg posted 06-09-2003 03:09 PM ET (US)     Profile for lhg    
JimH and others. Regarding the shallow splashwell in the older hulls, see my new "how to do it" message in the Performance section thread, "Did my Dealer install my engine wrong".

With Mercury engines, the blind hole does not exist, so that is not part of the solution.

roccus posted 06-09-2003 03:59 PM ET (US)     Profile for roccus  Send Email to roccus     
Hey Bigshot,

I went with a jackplate so that I use the existing transom holes on a 1968 Nauset. Botling new 90 directly to the transom would have required lagging the bottom two "screws," something I wanted to avoid if possible. The jackplate wasn't a performance issue.

I am encouraged by your suggestion of a 3-inch height (give or take) of ventilation plate above keel line. I was afraid that would create too much cavitation. I trust you haven't had that problem?


Bigshot posted 06-10-2003 11:06 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I was not sure I read your post right but I guess I did.

No issues drives like stock. You are gonna stain your shorts when you jack that puppy up. I am up over 4" with a 5" setback and I could probably go another inch but no need to. Go up at least 3" and test. Then go up another inch, etc.

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