C21 boat propeller pulls air when turning

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jacquesmm
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Re: C21 boat propeller pulls air when turning

Post by jacquesmm »

Thye do have several holes to adjust the height but the range isn't wide enough.
I always design the transoms to have about 3/4" extra in case the engine has to be mounted on the first hole. As designed, it is set for the 2nd hole.
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fallguy1000
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Re: C21 boat propeller pulls air when turning

Post by fallguy1000 »

Get a new engine. Ridiculous to cut up a boat and spend months on it.

The transom top, done right, is a lot of work. The benefit of a full heifht transom is apparent in big seas. And the splashwell may also be wrong.

Go to the dealer!!!
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fallguy1000
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Re: C21 boat propeller pulls air when turning

Post by fallguy1000 »

Sometimes, you can even just purchase the longer leg lower unit!!!
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fallguy1000
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Re: C21 boat propeller pulls air when turning

Post by fallguy1000 »

If you had a longer leg, if possible for that engine, it would take you about an hour!

An engine swap is a day of work.

The transom height, splashwell change could be a month.
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TomW1
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Re: C21 boat propeller pulls air when turning

Post by TomW1 »

I agree go talk to the dealer and tell them you made a mistake and need the 25", 63.5cm shaft and see what they will do for you. That is the best solution be honest and tell them how many hours you have on this one. You should not have many. It will cost you a few thousand euros but will get you the right motor.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

bartmatthijs
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Re: C21 boat propeller pulls air when turning

Post by bartmatthijs »

some thoughts on the above :

Finding a well-maintained, affordable second-hand 135 hp outboard motor is not really easy in Belgium-Netherlands.
And if you have to take into account the length of the tail, it will certainly be difficult.

Buying a new one was not really an option for me given the price! it is and remains ultimately a leisure activity.
(the total cost of the boat is already the best kept secret for my wife) :-)

So considering this is a second hand outboard motor, it is not really an option to trade it in at a dealer.

On the other hand it is only a small effort for me to shorten the transom as Jaques indicated (especially as this has no impact on the firmness of the boat)
Under the motto 'the way to it' is more fun than reaching the destination (In the end building is a hobby) I think I'll have this ready in a few weeks

Thanks you all for your help and advice and I post the outcome on the forum !

Bart

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Re: C21 boat propeller pulls air when turning

Post by bklake »

A manual jack plate or setback bracket seems like a far less intrusive fix. Bob's Machine is one brand. May not be available for you but worth a look.

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Re: C21 boat propeller pulls air when turning

Post by jacquesmm »

That is a good suggestion, no need to cut the transom with a jack plate. I don't think they exist in Europe.
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fallguy1000
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Re: C21 boat propeller pulls air when turning

Post by fallguy1000 »

Bob's in Tampa might be able to configure a plate for minus 5. Most are the other way. But in theory, it'd bolt in the other holes and sit back 6-8".

He'd need to tell them he wants to use a 20" engine on a 25" transom and see what they say. Then he may have some cabling and wires to amend.

Still easier to order a different engine with a longer leg, or find a blown engine and get the 25" leg and lower.
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TomW1
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Re: C21 boat propeller pulls air when turning

Post by TomW1 »

I think we need to look at another thing, if he cuts his transom down to 20" will his gas line, steering cables, and control cables still work or will he need to install new ones?

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

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