Tiki 21 Outboard issues

[Rob Wilkinson]

Well, got my Tiki 21 'Papayo' out of the water and dismantled to be covered up for winter..which is fast approaching my part of the world.

 

My Outboard Motor cavitates when I am motoring in choppy seas. Its a Yamaha 4stroke at 4HP, its powerful enough and I suspect its got the 'long shaft' option fitted. I am planning on removing about an inch from the top of the transom as the motor could then tilt up further and engage its final lock. would save its prop being dragged in the water. I dont like lashing the motor up in case I need to drop it in a hurry..ie a botched change of tack too close to shore :)

 

Seems to me that the prop could do with being a good 6 inches further down, that way in the choppy water it wouldnt cavitate so much, if at all.  Its annoying as it is because at times you need forward motion rather than having to throttle back and letting the cavitation subside.

 

 

[kim whitmyre]

Hi Rob,

The prop should be about the same level as the deepest portion of the keel for best level thrust.  Chop is a bugger, for sure! On my older 5hp 2-stroke, I did have to keep a hand on the throttle to prevent it from over-revving if the stern lifted high in the chop.  My new 6-hp 4-stroke allegedly has an automatic over-revving provision; I really haven't tested it out in serious chop as of yet.

You may be able to minimize the effect of the chop by not motoring directly into it unless its a necessity. In other words, "tack" into the chop when possible.

[Rob Wilkinson]

Thanks for the replys, yes I tend to take the chop on at an angle if at all possible. The props thrust line is nowhere near the bottom of the keels, so I might try sourcing a longer shaft for the motor. Dont want to buy another motor just yet, expensive little things:) 

[Galway Bay]

I dont have a 21 but I do love 'em !

I had a lifting "sled" type mount on my P 31 for years. The arms were  long  and the mount about the same height above the base as a normal transom.  In use once you got the boat going the support could be slackened right off and the sled base would "ski" along the surface  like a surfboard so the engine bounced up / down on the waves and kept pushing without over-revving. Mine was a bit crude and wet but the engine seemed to come to no harm. 

I had experience with a deeply immersed outboard. It ran fine once started but the back-pressure made it difficult to start. This especialy if it was not started immediately after lowering.

[Rob Wilkinson]

Hi, thanks for the pointer there, might just adapt your idea, my motor def needs lowering far more to be effective in serious chop. I need that assurance that I can still make headway if things get serious..ie looming coast line to the lee of me and having to drop sails etc...i just dont like the idea of getting caught out in an area that limited for gybing the 21 around.

 

 

[Roger]

Hi Rob,

I have exactly the same issues with my 21 and have also considered taking an inch out of the transom. My outboard is a long shaft 5hp Honda. It looks like the designed outboard height is a bit high. I think that Galway Bay's suggestion of a sled would work, but haven't seen one on a 21 yet. If I was wealthy I would get the extra long shaft Tohatsu (25").

[kim whitmyre]

That is the, albeit expensive, solution. . . I have the Nissan version  25" longshaft 4-stroke SailPro with the near-flat prop for thrust currently, and my old Nissan 2-stroke was also a 25" longshaft. This gets the prop to "proper" depth. :-)

[Robert Hughes]

Has anyone tried fitting an extra-large anti-cavitation plate to their outboard?  The motor on my T26 is mounted at the (theoretical) right height and works well in most circumstances, but in extreme pitching (say in a tide-race round a headland) it can suck air and cavitate.  I'm thinking of making a bigger plate from a flat sheet and bolting it to the one on the leg.

[kim whitmyre]

I have one of these installed:

It's not exactly an anti-cavitation plate, as it's actually to increase the thrust, but it does reduce cavitation in order to increase the thrust.

[Robert Hughes]

That looks neat Kim.  I might try something like that...

kim whitmyre said:

I have one of these installed:

It's not exactly an anti-cavitation plate, as it's actually to increase the thrust, but it does reduce cavitation in order to increase the thrust.

[paul anderson]

Kim first it was slings now extra thrust, things must be sporty over there.

[Rob Wilkinson]

So, say 25'' shaft..this would measure from transom sill to prop centerline? 

[kim whitmyre]

Rob,

Here is a shot of my transom/sled on my t26:

That is my old 2-stroke 25" longshaft in the picture, but the new motor hangs on the same transom. I don't have the actual measurements at hand, but will obtain them if it will help you.