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PostPosted: Thu Sep 13, 2018 5:19 am 
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Joined: Sun Apr 20, 2008 6:18 am
Posts: 2982
Location: Sarasota,Key West FL
I also had my motors mounted pretty high, I never measured but am guessing my Honda’s were around 6” above the gunwale. I had the short shaft honda 2.3 outboards, (2), mounted near the rod holders.
I had the motors mounted very close to the hull and tilted inward around 5-7 degrees so the props are under the hull somewhat.
Keep in mind I had a modified planing hull with much more flotation , (100 lbs extra flotation), and when underway, (planing) the boat ran much higher in the water vs most TI’s.
We were able to start the motors with the bow on the beach, and normally beached with the motor running. With two motor I could steer somewhat with rudder up and using motor rpm to steer in very shallow water, (lots of very shallow water around here at low tide).
One other trick we used in shallow water is to lock the rudder up around 15 degrees from horizontal and steer with just a small part of the rudder, (yea you can do that). We often sail thru 8”-10” of water, (lol usually not on purpose).
When solo I only ride in the front seat, (can’t stand that sailcontrol line on my neck), I had throttle extensions so I could operate the motors from the front. For a while I had extentions on the tilt up and starter ropes, but never used them, so they were removed, (too many ropes). We typically started the motors when we pulled out and just let them run all day, (Idling when not actively using them for power). Then shut them off when we came in.
FE

EDIT: We typically got around 3 hrs of runtime out of the motors per tank of gas (1 tank = 1 liter), (longer if we used them less, (motors were not primary propulsion on the boat), actually I don't recall having to fill up the tanks on the water very often, (though it wasn't difficult, it was still a little bit of a pain).
One thing you will find out with the Honda's is once they warm up, the idle goes up, and the clutches don't dis-engage completely at idle, as a result with the throttle all the way down, we couldn't go any slower than around 6-7mph, (with the motors idling), I typically had to kill one when coming in the harbor. Never did solve that one.
One other thing we did for a while was to stuff a big wad of silicone tubing into the exhaust port, of various lengths, (looked like whiskers). This made the motors totally silent, (lol we called it stealth mode). But we wouldn't try to run the motors at higher rpm with that setup, as it might overheat, (we limited to 1/4 throttle). That was fun for a while, but I ended up removing the tubes, at low rpm the motors are not loud anyway, we can easily talk over the noise without any tubes at all. Here is a video with the motors running, (no silicone tubes), you can barely hear them, (that day was a good idle day for the motors, they were idling very low that day), normally in that situation I would have need to kill one motor.

https://youtu.be/9jFCfBMZKKU


Here is a video of the boat planing on the water, (notice how high it is riding in the water, and the bow is out of the water). Normally at that speed, (without the hull mod), the stern is completely underwater because we are above the hull speed of the boat, (8.6mph is the hullspeed of the TI), and the stern wave has overtaken the stern without the hull mod. The hull mod delays the stern wave and moves it back a couple feet.
https://youtu.be/a1OjgyqBsXk


If I ever do another hull mod, it will be wider and flatter, (that one wasn't quite right, (first attempt)), and will be the full length of the hull, (making the boat 20.5 ft long), giving me an additional 200 lbs of flotation.


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PostPosted: Thu Sep 13, 2018 8:10 am 
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Joined: Tue May 30, 2017 8:59 am
Posts: 34
Location: Mudjin Harbour, Middle Caicos
Thanks. I think I'm going to go plan B since I'm not sure how high to raise the motor. I'd like to have it as high as possible since there are some very cool and unexplored shallow areas around here (Middle Caicos.)

Plan B -
I'll get 4 of these and bolt them to a wood board that I can cut until I get the right height. I can get wood at the hardware store on the next island over.
https://www.framingtech.com/corner-guss ... es-4-holes


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PostPosted: Thu Sep 13, 2018 9:25 am 
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If you mount the motor too high you run the risk of a form of cavitation if the prop starts to suck in air from the water's surface.


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PostPosted: Thu Sep 13, 2018 9:46 am 
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Joined: Tue May 30, 2017 8:59 am
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Location: Mudjin Harbour, Middle Caicos
Yeah, I understand that. My last boat was a 240EFI Merc Jet in a Sugar Sand where cavitation would happen when I'd beat on her. There's also some bearing that needs to be submerged on the Honda 2.3 to keep cool that I've read about. I'll have to figure out the height once I bolt everything on and take it for a spin.


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PostPosted: Thu Sep 13, 2018 11:24 am 
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Joined: Mon Dec 29, 2008 2:35 pm
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Location: Niceville, Florida
Mr Dunce, the back of my transom (where the motor grips) is dead even with the front edge of the rear hatch on my T.I. The height of my transom from top of gunwale is 8.75 inches as measured with Stanley tape. It worked very well with the Honda, for all of the 13 hours(over six months) that I owned it. It’s kind of funny now, if I start the motor with no one in the boat, you can really hear the exhaust from the Suzuki. Once we climb aboard it seems to be in the perfect position, nice and shallow for efficiency, yet never has an issue with digging in.

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PostPosted: Thu Sep 13, 2018 12:09 pm 
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Joined: Tue May 30, 2017 8:59 am
Posts: 34
Location: Mudjin Harbour, Middle Caicos
Thank you!


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PostPosted: Thu Sep 13, 2018 4:10 pm 
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Joined: Thu Aug 16, 2007 2:25 pm
Posts: 2775
Location: Central Coast NSW Australia
Head_dunce,
If you want to avoid waves hitting your mount then the bottom of the mount should be around 2” above the gunwale.
You’ve seen this main thread on outboard mounts? https://www.hobie.com/au/en/forums/view ... &start=330
On p23, second last post, is Jim Powers mount which is a great evolution of the ideas so far.


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PostPosted: Thu Sep 13, 2018 5:29 pm 
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Joined: Sun Apr 20, 2008 6:18 am
Posts: 2982
Location: Sarasota,Key West FL
I think the final motor height is a trial and error thing depending on where on the boat the motor is mounted, how far away from the boat the motor is mounted, (some mount them way out). So there is no one size fits all.

So it’s probably best to design so you can dial that height in. The main factor is cavitation, which is loud and easy to identify. Plus it might not cavitate on level water, but cavitates badly when on a left or right tack when sailing, (that was a problem on my first motor).
Also it make a difference if you have a shaft mod or not. If you watch my video you will see a white thingy on my motor shafts, those eliminate most drag and eliminates most cavitation, (keep in mind all outboards are designed to be mounted behind a transom, (behind the boat).
It might be better to design too low, then trial different shims until cavitation starts, then lower down slightly, then finish the mount to the final height on your boat.
Just suggestions that’s all.
FE


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PostPosted: Fri Sep 14, 2018 5:30 pm 
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Joined: Tue May 30, 2017 8:59 am
Posts: 34
Location: Mudjin Harbour, Middle Caicos
Thanks for all the help. I've ordered the brackets and a bunch of different size 316 ss bolts, washers, nuts, etc. to get this fabricated with a wood board I can pick up on the next island over. I'm going to be in the US for a night in a few weeks, so I'll be able to pick up everything I ordered (UPS Store's are great!) I also have the motor coming via cargo ship on a freight forwarder in a few weeks. So I'll report back once I can get everything together.


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