Motor Mounting Template

[Fletch170]

Hey guys,

Does anyone know a website that has a template for motor mounting? My 170 had a 85 Johnson (I think) on it, and I'm slapping a 155 2s yami on her. The hole patterns are different. What is the best way to to get this done? Existing templates? Make one from the back side of the motor mounting surface? I just want to make sure I have the height correct....or at least have the damn thing centered correctly. I'm a novice, please point me in the right direction.

[Capt. Bob]

Hey guys,

Does anyone know a website that has a template for motor mounting? My 170 had a 85 Johnson (I think) on it, and I'm slapping a 155 2s yami on her. The hole patterns are different. What is the best way to to get this done? Existing templates? Make one from the back side of the motor mounting surface? I just want to make sure I have the height correct....or at least have the damn thing centered correctly. I'm a novice, please point me in the right direction.

Different?
http://classicaquasport.com/smf/index.php?topic=8436.0

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Try this:
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http://www.thehulltruth.com/attachments/boating-forum/207437d1323350040-outboard-mounting-template-help-backing-plate.pdf

Ton of stuff on the different boat forums, all seems to follow the same (bolt) pattern. Yamaha may sell a template, phone call would confirm. <!-- s:idea: --><!-- s:idea: -->

[Fletch170]

I will check tese out. The bolt pattern that was in the transom def does not fit the yamaha. The top 2 holes work...the bottom ones do not.

[fitz73222]

OMC did have an alternate set of lower holes that could be used. The reason was for boats with shallow splashwells that had limited or no access to the standard location in order to tighten the bolts up. Every 17 Whaler we rigged had to use the shallower lower hole pattern in order to be able to bolt the engine up correctly. If you can; temporarily mount the Yamaha using the top two bolt holes and transfer the lower holes from the bracket or just use the mounting template provided and drill the lower two holes in the correct location and plug the old alternate hole pattern from the OMC bracket.

[wingtime]

Be sure to check the height of your cavitation plate in relation to the bottom of the hull before you drill!  You did measure the "ride height" before you took off the old motor right?  Not all manufactures 20" or 25" shafts are the same length.  You don't want to get the thing all mounted up only to realize you have to move it up or down and you drilled the lower holes wrong.  (don't ask how I know this).  Also this goes without saying fill the old holes with 5200... even better plug them with a wooden plug and epoxy.

[Fletch170]

I've already plugged, filled and glassed the old holes. So, I'm starting from scratch.

From what I've heard, you want to have the cavitation plate 1/2 inch ABOVE the height of your keel?

Please let me know if I'm wrong about this.

[seabob4]

1/2" works good, pretty standard initial setup.  May need tweaking once you get up on plane and actually see where the cav plate sits in relation to the water level.  It wants to be just getting wet...

[Fletch170]

I looked on the yamaha website, and they say level with the keel, WTF? Are they just making sure people don't blow up the motors?

[GoneFission]

I looked on the yamaha website, and they say level with the keel, WTF? Are they just making sure people don't blow up the motors?

Yes.  Not blowing up motors is good.  

[Capt. Bob]

I looked on the yamaha website, and they say level with the keel, WTF? Are they just making sure people don't blow up the motors?

Yes.  Not blowing up motors is good.  

My guess is that the Factory is more concerned about the handling ability of the boat (think hard turning) dependent on the mounting height than the water/excessive rpm. Liability (life safety) would be more of the legal department's concern.

I'm just sayin'.

[Fletch170]

Meh Safety Schmafety.

[seabob4]

A little OEM info.  When we came out with the 20 Sport at Proline in '06, my Suzuki guy and I went out on Crystal River with the sole purpose of getting the cav plate exactly as we have described here in this thread...just getting wet.  Zuke 140 4S.

So I'd say Zuke is happy with our recommendations.  And really, from an LU standpoint, not that much different than a Yammi...

[Fletch170]

So, I want the water to just fold over the aft section of the cav plate with 3/4 throttle at a level trim. Roger that.

[seabob4]

So, I want the water to just fold over the aft section of the cav plate with 3/4 throttle at a level trim. Roger that.

Pretty much.  The way to check properly is to get a hold of a long, stiff straight edge, hold it flush against the keel, trim the motor so that the fore and aft portions of the cav plate are equidistant from the straight edge, measure that distance.  I would prefer the underside of the cav plate to be 1/2" above the straight edge.

Not that it's the same in this case, but builders typically design transom heights such that almost all motors are mounted in the second hole down from the top when they roll out of the factory...

[Fletch170]

Who knows with my boat......I believe mine was made at 4:45 on a friday before the Bicentenial office party (76 boat).