Advice on outboards on yachts

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ManniB

NSW

15 posts

ManniB

NSW, 15 posts

8 Mar 2010 11:14pm

Hi All,

The saga continues with my Pelican 27. I have had a Yamaha 9.9 HP long shaft High thrust o/board put on with electric start and forward controls. The well known company at The Spit that installed it are telling me that I now need a extra long shaft. The motor is on an angle that is, the prop is aiming upwards by about 20deg from the horizontal and the cavitation plate is approx 100mm underwater. When forward in calm water is selected it goes OK although it does bounce out in a chop and sucks air. IN reverse it is useless the upward facing prop creates a vortex and sucks air down.
Does anyone have an outboard on a small yacht that could advise as to how far down should the cavitation plate be and should the prop be on the horizontal or facing downward a few degrees?
I am not as experienced as many of you but commom sense tells me that it should not be pointing up.

ANy help and advise would be much appreciated.

Regards

Manni

Ramona

NSW

7754 posts

Ramona

NSW, 7754 posts

9 Mar 2010 8:42am

Manni,
My Lexcen quarter tonner has a 8hp outboard mounted centre on the retrouse stern. Its a fixed bracket, when sailing the motor is tilted up and the skeg is well clear of the water. When motoring the motor is vertical and the cav plate is about 100mm under the water. Its a long shaft 8hp Mariner. Motors well in flat water and reverses OK but the large rudder blade makes for some excitement if not prepared for the tiller leverage. Sloppy water its hopeless really and its always better to sail.

Sounds like your dealing with "professionals". Presumably you have tried adjusting the pin position to get the motor more vertical? The height should not be a problem and if it was, just rebolting the bracket lower would fix it. Sounds more like an angled pad is required to get the angle right. Wander about the marina and moorings with a digital camera and see what the others are doing.

My next yacht will definitely have an inboard diesel

maxm

NSW

864 posts

maxm

NSW, 864 posts

9 Mar 2010 8:49am

Manni,

The outboard leg needs to be vertical. Which means the cavitation plate should be horizontal.

I don't know the Pelican 27 but if the head is forward of the prop then I'm guessing that's because the outboard is mounted on a sloping transom. Is that the case? If so then you probably don't need a longer outboard, you need an outboard mounting bracket. This kind of thing -> ~~http://www.biasboating.com.au/p-1824-galvanised-outboard-bracket.aspx~~

MichaelR

NSW

862 posts

MichaelR

NSW, 862 posts

9 Mar 2010 3:08pm

Manni, as you know I've replied personally about this, hope you get something sorted soon.

For the others, this is the better bracket "in my opinion". It's more adjustable and is way more solid than the Bias one mentioned. It's stainless too.

maxm

NSW

864 posts

maxm

NSW, 864 posts

9 Mar 2010 6:36pm

Thanks MichaelR for pointing that out. I didn't intend my link to be read as a recommendation for that particular bracket, but just as an example of the type of bracket I was talking about. In fact, I've no experience with any of the brackets currently on the market. The only thing like that which I've used came with a boat I had some years ago. It was supposedly rated to carry up to 15 hp but it cracked carrying my 8 hp outboard!

So yes, please have a close look at the construction... it's probably worth paying extra for a good one.

Ramona

NSW

7754 posts

Ramona

NSW, 7754 posts

9 Mar 2010 6:49pm

I'm not sure what stern the Pelican has but the bracket does not need to be very complicated. Ramona's stern just happens to suit this style.

ManniB

NSW

15 posts

ManniB

NSW, 15 posts

9 Mar 2010 10:58pm

Ramona said...

I'm not sure what stern the Pelican has but the bracket does not need to be very complicated. Ramona's stern just happens to suit this style.

Hey Graham,

how far in the water does the cavitation plate sit when lowered?

Cheers

Manni

Ramona

NSW

7754 posts

Ramona

NSW, 7754 posts

10 Mar 2010 8:47am

ManniB said...
[

Hey Graham,

how far in the water does the cavitation plate sit when lowered?

Cheers

Manni

I've never measured it but I would say not far. Weight in the cockpit would put it down a bit more. I sail solo most of the time and if I stand on the bow while motoring the prop cavitates. I either sail onto my mooring or slip the motor into neutral and walk fwd.

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