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Old 26 December 2011, 13:35   #1
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Country: UK - England
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Daft newbie question

I have a 40HP 2 Stroke Yamaha c1990 that I am renovating and servicing at the moment.

Being a total newbie to marine engines theres a lot of reading of manuals etc before i actually start spannering.

On of my next tasks is to change the impeller which in itself doesnt seem too onerous a task but where im a bit confused is that there doesnt appear to be any mention of gasket of other form of sealing ring between the leg of the engine and the lower unit.

Is this right? Any naughtiness i need to be aware of?

Cheers
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Old 26 December 2011, 16:48   #2
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That's correct no gasket or seal is required between the mid-section and lower unit
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Old 27 December 2011, 05:47   #3
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The gaskets (if there are any) will be inside - I dnlt know this engine, but as a general rule there are four things pass through the leg - drive shaft, cooling water supply pipe, exhaust and gear shift linkage.

Needless to say the prop shaft has an oil seal on top of the gearbox, and will spline into the bottom of the engine. THere are variuls ways of sealing the water & exhaust pipes, but you should get all the bits ytou need for the water pipe in the impeller kit.

Some mercs used a rotating gearshift, which just splined together, others you have to disconnect the shift shaft at one end. Youre manual will explain in detail.

The one screw that usually catches new people who spend hours trying to free the gearbox from the leg is the one hidden under the trim tab (behind the prop).
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Old 27 December 2011, 09:02   #4
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Thanks guys. Armed and dangerous with a spanner, impeller and now knowledge!
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Old 27 December 2011, 09:26   #5
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I used to have a 1995 6H4 40V Yamaha. Fantastic engines.

One thing to be aware of once you've dropped the leg to reveal the water-pump housing. If the woodruff key is fused to the driveshaft (where the impeller locates), then don't force it apart - leave well alone. Remember to grease the impeller housing with light coat of marine grease. Turn the driveshaft clockwise (the impeller will rotate) and push the water-pump housing into its final position. Torque bolts, etc. Let us know how you get on.
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Old 28 December 2011, 02:07   #6
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Hi

Great advice has been given so my only comment is .... there is no such thing as a daft question re boats and engines, there is only bigger bills for not asking so please ask away as we all started knowing nothing.
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Old 28 December 2011, 03:31   #7
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Quote:
Originally Posted by clydeoutboards View Post
there is no such thing as a daft question re boats and engines
+1
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Old 01 January 2012, 14:13   #8
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Quote:
Originally Posted by LHTEC View Post
I have a 40HP 2 Stroke Yamaha c1990 that I am renovating and servicing at the moment.

Being a total newbie to marine engines theres a lot of reading of manuals etc before i actually start spannering.

On of my next tasks is to change the impeller which in itself doesnt seem too onerous a task but where im a bit confused is that there doesnt appear to be any mention of gasket of other form of sealing ring between the leg of the engine and the lower unit.

Is this right? Any naughtiness i need to be aware of?

Cheers


is the 40hp like my 30hp?

caution; Hi I have a 2002 Yamaha 30hp 2 stroke. I have change the impeller several times. its very straight forward, but if it is the same as mine make sure you undue the gear linkage, otherwise you will yank the gear selector out of the bottom leg like i did!
I found the above link useful.
have fun. Mike
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