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YAMAHA, OMC and MERCURY have similar histories:

MERCURY had 650, 700, 50 hp and 60 hp 3 cylinder 49 cubic inch short Shaft motors sold by dealers.
The 650XS was a different motor and was special order from Mercury. Mercury did have parts for the 650XS available through dealers until the parts supply ran out. Power head and other 650XS parts are difficult to find. Best source is EBAY.

OMC Short Shaft 3 cylinder 49 cubic inch motors started in the late 60's with a 55 hp model. The motors from then until 1988 could be purchased through dealers. In 1988 OMC produced the last 49 short shaft model called Formula E. That motor was sold by Second Effort Marine in Florida. Once that production was sold out, no more E motors were manufactured. Parts for the nitro gear case were sold through dealers and that stock has slowly disappeared. Sea Way Marine was the last one to stock nitro inner parts. Power head parts are no problem.

http://www.boats.net/parts/search/BRP/E ... parts.html

YAMAHA was more complex. Yamaha produced a wide variety of 70 hp short shafts. Depending on where they were sold in the world. Yamaha Canada had different models and parts access compared to the USA and Europe has different models compared to both Canada and the US. Yamaha USA did not have access to 70 hp short shaft parts or Yamaha 55 hp motors for parts. Hydro Tec was able for a few years to buy 70CES [6J2 model] parts directly from Japan and not through Yamaha USA. Dealers in Europe were able to buy a 70CES direct from Yamaha. 70CES were produced as needed, normally one production run every year or two. It was possible to buy one from a dealer in the US. Those dealers did not get them directly from Yamaha USA or Yamaha Europe, but from mostly dealers in Africa and Asia. That is where many of the used 70CES came from as well. Florida was a good place to find motors because of SLT racing.
Enter MARINER...In the late 70's until 1985 Yamaha produced the 48, 55 and 60 hp 2 cylinder Mariner. Unlike the Yamaha which had many different versions for different world markets, there were fewer models of the Mariner. MANY of the short shaft parts for the Mariner were the same as on the 70 yamaha short shaft and they were sold through the Mariner dealers.
Here is a list of what parts come from what motor. NOTE: MOST PARTS NEED TO BE PURCHASED USED.
- 70 hp 15 inch mid...It has to be Yamaha. They were on the 53 cubic inch 50G short Shaft, 70B short shaft [you could only buy the parts in Canada not a complete motor from the 1992 parts book, I got a mid from Yamaha Canada in 1998] Britain or Europe occasionally will have parts on EBAY.
- 15 inch 1:71 short shaft gear case is from a Mariner 60 hp short shaft. 15 inch 70 yamaha drive shaft is rare, other parts are common and some are still available new from Yamaha Canada,
- the 70 hp yamaha non power trim clamp bracket assembly is from a 48, 55 or 60 mariner short shaft
- the 70 hp yamaha power trim clamp bracket is from a Pro 50 Yamaha late 80's to early 90's...3 ram type
- what makes a 70CES are the 6J2 parts. There were 2 models of the 70CES, the late 80's version and the early 90's version.
Most did not replace their early version with a new power head etc., they just purchased the newer parts. UIM changed the spec sheet to the new parts so people were forced to buy them. A tuner was 500 dollars and a cylinder head 600 dollars.
- 70CES tuners, because they rust out and 70CES cylinder heads are difficult to find. After market and Yamaha Canada can supply the rest.

We did have a NEW, 100% stock, original, numbers matching 70CES in T850. The record for T850 is 66 to 67 mph. That is EXACTLY the speed this 70CES ran. We had a perfect yardstick to compare other T850 motors and especially parts built 70 hp short shaft Yamaha motors. Stock to Stock there was no difference in the yamahas. With our current T rules in is easy to build a 70 hp yamaha and they have shown to be BETTER on a T boat compared to the original 70CES. Unless you want to spend the money on 6J2 parts just to be original, YOU don't need to for T850.

Here is the 6J2 parts book...This motor came as a short shaft only.
http://gjoel-marinecenter.dk/upload/YAM ... 2100E1.pdf

Mariner long at short shaft models
http://www.boats.net/parts/search/Merc2 ... parts.html

Great Post, Don.

The parts in that PDF are 20" shaft only, right?

do you have any part numbers for a short driveshaft and short "upper casing" (mid) for the 850cc 3Cyl 70/50G/etc?

The 70CES 6J2 only came as a short shaft. That PDF is ALL and only short shaft parts. I added the Mariner parts list to the post. The Yamaha and Mariner have different part numbers for the same part, but it is the same part. The Yamaha mid part number is the short shaft part number.

T Class and EP [up until early 90's] was a NO power trim class. For many it is far easier to drive a T style boat without power trim because it eliminates the over trim aspect and most of the hooking in the corners. You just balance the boat different and set the boat in the turn by a quick throttle lift to drop the nose. Factory power trim adds weight to the transom. IF? you wanted to go no trim on your 70 hp long shaft Yamaha use the long shaft clamp bracket assembly off a 48, 55 or 60 hp long shaft Mariner. It bolts right on and it also fits a 90 hp long shaft Yamaha.

Thanks Don,
I'm just looking to see how feasible it'll be to convert the long Yamaha 70 and long 2Cyl Mariner 60 to short shafts.

I did find a 1993 50G(62F) 60F(6H3) 70B(6H3) parts catalog that shows both long and short shaft part numbers. Could likely use those parts to convert a 20" 70.

There's a short Mariner 60hp 2Cyl for parts on ebay UK right now but I'm not sure about going down that path at this time.

BTW, that parts catalog you liked the PDF to is 70CE, not 70CES. Does the "S" not mean short? so no "S" means long?

Ok, so the my 50G parts catalog shows the -00-EJ suffix as short and the -10-EJ suffix as long, so I'm guessing that 70CE catalog -00-EJ is a short shaft. (might have just answered my own question there)


I think this is the short mid for a Yamaha 70: http://www.boats.net/parts/detail/yamah ... 01-4D.html

Edit: So I found a Parts Catalog that says the short mid for the 850cc 3Cyl is 17.5". are all Yamaha mids for the 850cc that length? or was the 70CES 15"?

70CES stands for Competition Electric Short....There is another model called 60C which the C stands for Commercial ...then there are the Enduro models which are a little different again.
I have not found any yamaha short shaft model 30 to 70 hp where the short shaft is an exact 15 inch like the Mercury or OMC. Some like the 30 yamaha are well over 16 inch. The 70CES is a little longer as well. A long shaft 70 hp yamaha with the big foot is approximately 20.5 to 21 inch. By switching to the smaller 55 hp foot the length is a little over 19 inch.
The confusing part is all the models of the same horsepower. Different part numbers for what could or could not be the same parts. The last 2 digits for parts such as mid or gear case is the colour of the paint,

If you're looking to do a 15" just get it cut. I gave up looking and just had Gieger/Top Gun/Kawartha cut weld and paint it.

If you're looking to race T850 get an OMC...end of story.

If you insist on running a Yamaha I've got the UIM spec sheet for the 70CES.

You find different YAMAHA 52 cubic inch models all the time.
A 50G is short shaft with the smaller 1.71 case.

Here is a 1996 60 hp short shaft with appears to be the large 2:33 case OR is it the small case??
Nice looking motor.
https://www.olx.co.za/ad/60hp-yamaha-sh ... 5NJKe.html

that looks like a ces case to me . i don't think they ran a cotter pin in the larger 15 spline shaft .
could be wrong tho.