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Old 18 December 2012, 08:57   #11
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Engine length

Hmmmm, it does look very high on the transom. I always believed the cavitation plate should be roughly level with the bottom ot the keel?
Best to try out first tho & see if it ventilates?
If so, the engine may be a 'short-shaft' model. I believe you can get a kit to extend the length of the engine.
I wouldn't go cutting the transom down just yet!
Good luck!!
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Old 18 December 2012, 09:02   #12
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...and the specs for the 410 are here, it is designed for a long shaft motor. However, IIRC, Tohatsu shorts have a "tendency" to be a bit longer than some others. You may find that it works just fine. If not, I'd trade the motor before I'd touch that transom. You'll pay the price at sale time if you do...
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Old 18 December 2012, 09:03   #13
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There are 3 more photos of boat in the bucket if you go right... above...
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Old 18 December 2012, 09:13   #14
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I agree, cutting the boat up is a last resort. As I said, the last owner ran the boat and states it ran very well only 'cavitating' when on full power and a very hard turn.

Looking forward to using the boat, and hoping I get reasonable performance for a 30hp. Owner stated he saw 25 - 27 knots on the GPS. (low drag setup, lol....
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Old 18 December 2012, 09:34   #15
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I would be more concerned about how you are going to fit the tow bar to the green car given the location of the exhaust

Bet of luck with the new purchase
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Old 18 December 2012, 10:04   #16
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Definitely previous owner purchased a short shaft engine for a long shaft transom, had exactly the same issue as yours. In flat calm waters and near straight course no problems, excesive ventilation issues on choppy seas and close tight turns. In my particular case ended chopping transom down to match my Tohatsu to my 420 rib.

Chopping transom down would be the last resort for rib/engine to perform as expected, as probably impossible to change engine for a long shaft. The only small issue I find using a chopped down transom is slight water comming at transom area when reversing engine, a matter to reverse with less throttle. Other than that the combo flies with just a 18 horse. If needed can post pics of the modification.

Happy Boating
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Old 18 December 2012, 10:49   #17
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''as probably impossible to change engine for a long shaft'''

what do you mean / why do you say this?

I would like to see your installation. Only 110 - 120kg base boat weight, so massive power not neccessary.....

sold the green car days after buying this boat.... never told new car owner is was a tow car...lol....
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Old 18 December 2012, 12:25   #18
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Quote:
Originally Posted by Johnscubanut View Post
Hmmmm, it does look very high on the transom. I always believed the cavitation plate should be roughly level with the bottom ot the keel?
I've always heard that's a starting point.

Once you get the motor mounted, it's trial and error tweaking stuff until it works for you. I've seen some boats run with the anti-ventilation plate way above the keel (and some that need to be a bit deeper.)

jky
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Old 18 December 2012, 12:39   #19
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Here's an image of my old Valiant, I had the opposite problem, the engine was too low in the water and I was getting vertical fountains of water and pretty poor performance, every time I raised the engine things improved and then I ran out of holes, I ended up an inch higher that shown here.

As far as I'm aware the cavitation plate needs to sit level water line left by the back of the boat, too low and it will either cause drag or raise the back out of the water and make it less stable.

Your's doesn't look too bad to me, if it is wrong then buy a new motor before you get your chainsaw out, as soon as you start hacking it will be worthless. You can convert some motors between long and short shafts and it's not as expensive as you might think as long as the parts are available and you've got some basic common sense.
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Old 18 December 2012, 17:23   #20
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Quote:
Originally Posted by simsy View Post
''as probably impossible to change engine for a long shaft''' what do you mean / why do you say this? I would like to see your installation. Only 110 - 120kg base boat weight, so massive power not neccessary.....
Was reffering that you have a short sgaft engine when needing a long shaft one, so probably changing, selling, buying a long shaft engine is not the way to go for you.

In my particular case my rib's keel to transom distance is 46 cm, this gave excellent speed in flat calm waters at straight courses, excesive ventilation at choppy seas and tight turns. Chopped transom dowm 5 cm to 41 cm and rearranged both engine plates to transom level, have reached the best transom height for best speed and inmaculate tight turns at wot. Engine is reving at 5600 (top is 5800) at 40 Km/h. My rib/engine combo weights 150 Kg.

Is not that Tohatsu has a larger lower leg, it's just it's tail design, a bit different that other brands lower legs. The distance stated on owners manual is just a refference from where to start, if you want ribbing perfection you need to fine tune engine height, most people just sits engine matching same size leg to same size transom and that's it, but are losing the best engine performance that can be taken out from any engine.

Trimming engine all the way down is no the way to go, rib will tend to bow excesively down. With engines that dosen't have electric trims you just need to have engine sitting perpendicular with a well ballanced boat. No need to be constantly playing with trim. This is the perfect height for your engine, check video.



Happy Boating
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