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Old 04 July 2011, 23:40   #1
kubcat's Avatar
Country: Australia
Town: Sydney
Boat name: Lunasea
Make: Ribtec 890SX
Length: 8m +
Engine: Yamaha ME 421STI x 2
Join Date: Aug 2009
Posts: 471
Yamaha sterndrive question for the experts

There appears to be at least 2 different Yamaha Sterndrives.

One is the Hydradrive in single and duo prop as found on diesels and 7.4 petrol V8's and the other is a single prop unit found on smaller petrol engines.

The upper half of the gearbox looks quite different, but the bottom half looks very similar.

Does anyone know if they interchange or if they interchange with anything else like a Yamaha V6 outboard gearbox?

If they do, the next question would be if the ratio is determined in the upper or lower part of the sterndrive as with the small petrol engine version there appears to be a number of different ratios depending on the horsepower.

Also, as there was apparently a copyright issue that stopped them being sold in the US, do they interchange with the unit they supposedly copied?

Thanks in advance.

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Old 05 July 2011, 14:16   #2
Country: UK - England
Town: Colchester
Boat name: Project
Make: Atlantic 21
Length: 6m +
Engine: Mariner 2.5 v6
Join Date: Mar 2010
Posts: 44
I think in this case the older drive found on the YEMS 5.7 and 4.3 is a dog type gear box only seen a few. Would say no to the lower units and an outboards got a much longer input shaft than an outdrive.

The hydradrive is only one ratio but there are a few types in SP and the TRP.
Dont think a lot changes on them I know we have run older lower units on new tops.

I may be wrong but someone can correct me if so.

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