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Old 29 October 2011, 06:17   #1
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New engine height

My mate is mounting a new engine on his new rib, any tips on how to work out the engine height ?

Its a 5.2 m rib with a long shaft engine on a 20" transom.
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Old 29 October 2011, 09:07   #2
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Short shaft is wat u need , only way out is fibre glass 5 " to top of transom or buy a jack plate
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Old 29 October 2011, 09:19   #3
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I think Sea Witch may have misread your post. Your mate has the right engine length. General recommendation is to have the anti-ventilation plate level with or slightly below the bottom of the transom when in a neutral trim position.

I suppose there are more accurate specs for a particular hull/engine/load/prop combination. If you state RIB type and engine model, I'm sure someone on here will have tried it.
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Old 29 October 2011, 09:20   #4
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No you don't need a short shaft as they are on 15in and won't reach!!!

The new motor should come with a transom template which can be used to drill the locating holes for the first time.

Shaft lengths are confusing now on new motors as most new sales refer to a standard shaft being the 21 inch model with the 25in shaft now known as the long. Most people are used to the older system, when told long assume it to be 21in and call the 25in an XL.

Not that it matters as you have the engine it's just your trying to find where exactly to bolt it onto the transom ?

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Old 29 October 2011, 10:39   #5
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Quote:
Originally Posted by Boats&Outboards View Post
Shaft lengths are confusing now on new motors as most new sales refer to a standard shaft being the 21 inch model with the 25in shaft now known as the long.
Outboard manufacturers still use Short, Long and Extra Long or refer to the Transom depth in inches, 15", 20", 25". I've never seen Manufacturer specs referring to a "Standard" Shaft. It's dealers who use confusing terminology.

Long is 20", not 21".
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Old 29 October 2011, 12:53   #6
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Quote:
Originally Posted by willk

Outboard manufacturers still use Short, Long and Extra Long or refer to the Transom depth in inches, 15", 20", 25". I've never seen Manufacturer specs referring to a "Standard" Shaft. It's dealers who use confusing terminology.

Long is 20", not 21".
That's my point, new retail sales, not the manufacturer. your right the builder refers to the transom height but th dealer the "shaft length"

Long "shaft" is 21 inches to fit a 20 inch transom giving the facility to fit it "off the transom" Measure your "long shaft" I bet it's 21 inches to the cav plate

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Old 29 October 2011, 13:51   #7
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Quote:
Originally Posted by Boats&Outboards View Post
Measure your "long shaft" I bet it's 21 inches to the cav plate
No, the Long I have to hand is almost 23", the Short one is 17". They're generally referred to by the intended transom length, not the actual measurement of the motor.

Your eBay page has me even more confused:
"short shafts are around 15 inches, Standard outboards are around 18 inches and the long are around 23 inches. You measure the outboard length from the outboard's bracket that sits on the boats transom to the cavitation plate just above the prop as shown below. Easy as that right ?? wrong, be careful, standard shaft is often referred to as short shaft and vice versa. To confuse things more there are some boats that require an extra long shaft, normally around 25 inches, these were made simply to confuse you, no ok there of course serve a purpose for larger transoms but are very rare and hard to obtain"

If you need any very rare 25" motors, I'm sure I could scout a few for you...

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Old 29 October 2011, 13:55   #8
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That was written a very long time ago and is out of date at a time when an XL shaft was not the "norm". It relates to smaller engines.

Thanks for the heads up I'll edit it.

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Old 29 October 2011, 17:30   #9
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Hi Boats and Outboards, yes, the bolt hole is what I am after help with. The RIB was brand new and had never been in the water however it did have an outboard fitted but never used so the holes are all there, its just a guide as to where the cav plate should sit I guess.
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Old 29 October 2011, 17:34   #10
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Would recommend to check the distance to cav plate before drilling in any case. As an example, 25 hp Tohatsu, differenced between 25 hp 2 stroke and 4 stroke (short leg) engines is 1.2 inch...

2STROKE/Dimensions
Short rig, distance to cav plate is 17,1

TLDI/Dimensions
Short rig, distance to cav plate is 15,9 inch
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