MercTrans to VelvetDrive Conversion
 

Hi All,
I have a '81 Scarab that came stock with the MercTrans Transmissions. The boat has been re-powered with Merc 420's that have had work done so that they are putting out more HP then from stock...anyway, I have owned the boat for over 10 years and it has always been plagued with problems with these tranny's....I have an opportunity to pick up a couple of Velvet Drive Trans for almost nothing, what I need to know is what it is going to take to switch over to these transmissions? What additional parts I will need etc...etc... I want to try and have everything I need to do the conversion by springtime, so there are no surprises and last minute hustling to try and find parts!
The Drives on the boat are TRS, Here's what I assume I will need right off the bat. The drives were bolted to 327 small blocks, so I assume the Bell Housings will work on my BigBlocks.
1) Engine to Trans Couplers? Will the MercTrans Couplers work?
2) Some kind of rear mount with a Gimble Bearing?
3) Longer Drive Yoke?

Some other questions are;

Will the engine mounts need to be moved forward?
I have not seen these Velvet Drives Yet, nor do I have any numbers off them yet...is there a specific drive number or type that I need? What ratio are my MercTrans Drives 1:1? My existing setup counter rotates in the drives...are some velvetdrives counter rotating and if so how do I know how to tell?
Any other insights that you all may have would be greatly apreciated!
Thanks,
Mike

I have done this conversion, but its been 20 yrs ago when the parts were easy to come by.* When you check out the trannys make sure the coolers and lines are there the Merc tranny had cooler inside and has water lines to trans.*The warner 72C only runs one way,* you'll have to switch prop shaft to a left (forward gear is moved to front of case) I think the Merc tranny runs the same way.* Double check drives they already maybe a left & a right. The Waner uses a longer input shaft.* Motor must move forward. I think its something like 8" so make sure your not into your back seat.* The trannys both have different input shaft so plate on flywheel is different and I think the bolt pattern of tanny to bellhousing and not the same.* I tryed to check the parts for you but the pictures are no longer in Electronic Parts Catalog on computer.* You may be able to down load the parts pictures on line. If not and you need the parts picture & numbers to check which parts are needed or interchangable. I have them in the old printed parts books .* I can scan them.* I think I have left hand & right hand prop shafts and Waner input shafts used & NOS.* They are still aviable in the Merc parts and Accessory Catalog but not in the Elec. Parts Catalog.* Hope this helps.* I'am sure someone who* has done this swap recently will respond.

Thanks Cluster,
You have answered a LOT of my questions...in regards to the prop shafts, I only have to change it IF the new trans's are counter rotating right? because right now I have a left and right outdrive. PM me and let me know how much you might want for the input shafts that you have, both new and used! Damn 8" I did not think it would be that much...I am not sure I have that much room, it will be close, but it is not my back seat it will be hitting, There is a fiberglass "Shelf" in front of the engines that my Batts sit on..the fron edge of that wall is like a "Bulkhead" that the main stringers butt up to...not sure if you understand that? Anyway I am hoping it is a little less then 8".
How does the rear Tail Housing of the Velvet drive get supported...is there some kind of rear mount I need?...again this might all be with the transmissions as I have not seen them yet!
Thanks Again,
Mike

If u have a CW and a CCW drive then there is no need to change anything on those.
Find 2 nice regular BW C 72's or Hubers ...and get-r-done !
Oh, and most all of them are 1:1 ratio.

The transmissions all turn the same way. The counter rotaion on TRS is done in the lower unit. Other then that, yes the input shafts do need to be changed over, and you will need to install tranny coolers, flex plate... and you will need to move the engine forward a couple inches.

Thanks 30,
Can you tell me how to Identify what these drives are? Will They have C72 Stamped on them or is there another number I am looking for?

Never mind this last question I found the answer here http://www.boatgears.net/VDM.php#stright_through_models .

You are going to need bellhousings for starters. Merc trans are aluminum and have the bellhousing made on them. B-W's are steel and much heavier. Also I believe you will need to go to top mount starters, not positive. 72c's will have a green metal tag on them. They come in several ratio's, you will need 1:1. You will need coolers. You will have to change the input shafts on the drives at the u-joints. The rear mounts on the two large blocks on the transom plate with holes through them. Overall it is about 9" longer.No gimble bearing, there is a bearing in the tailstock of the trans (both merctrans and B-W).You will need different drive plates which bolt to the flywheel (couplers).If you have electric shift on the Merc Trans then you will need cables,shifters and associated linkages. Here's a pic a B-W, note the rear mount.
http://cgi.ebay.com/ebaymotors/Mercr...item23001026db
By the time your finished you will have more money, time and aggravation than it is worth for a 30 year old boat. If the Merc Trans are set up right and maintained they should be fine with those engines. Here's a guy that specializes in the Merc Trans.
http://www.kcmarinetr.com/Default.aspx

Hi picklenjim,

Thanks for the reply, Just curious though... is there a difference in the bell housings For a Small block B-W and a Big Block B-W? Because as I said in a previous post the transmission that are being given to me were bolted onto some 327 small blocks, I would think that the bell housings would be the same, but maybe I am wrong?

Also, Thanks for the link to the ebay picture...I have seen many pictures of other B-W 72c's that dont have that mount on them...is this specific to TRS Drives? If the ones I can get for free don't have these mount can they be converted? Is it just a diferent Tailstock on the trans?

I wish I could figure out why I have such problems breaking these MercTrans Transmissions, otherwise I would not be considering this conversion, but I break one of these things about every two years, and it is usually right in the middle of the boating season and then it takes me in the least two weeks to get the parts and then another week to get it together, 3 to 4 weeks out of an already short boating season (Cleveland, Ohio), is really a pain!

As for the boat being 30, She is in pretty good shape for an old girl, and I happen to like the classic look and style of the older Cigerette Style Boats, the new ones just don't look as good, and most of them sit way to high in the water for my taste, not to mention she is paid for and I would rather stick my money into keeping a classic running then to spend Upwards of $150,000 or more to buy a newer one.

BTW When I need parts for my TRS's I usually buy from Kirk at KC Marine, me and him have been scratching our heads with this problem for several years, and trust me I have tried EVERYTHING both Him and Myself could think of to keep these merctrans running, but to no avail! I will say that part of the problem is probably that I do take this boat out and use it the way it was intended to be used (I beat the snot out of it in some pretty big water on Lake Erie) Constantly "Getting Air" So that might be the cause of some of the "Stress" on these Trannys.

Anyway Thanks Again for the Info,
Mike

the info u posted is for transmissions, not drives !
maybe i misunderstood u ?

I am wondering why dont u just sell the TRS stuff and buy 2 used bravos and rerig the boat, lot cheaper in the long run and u will gain speed and power over the current set up ?!

The bellhousings should bolt to either. The trans in the picture has a tail stock on it for a sterndrive, TRS. The B-W's were used in a lot of inboard applications in which they have a flange at the output shaft to connect to a straight inline propeller shaft. They also had a v-drive model. They came in several different gear ratios. These are the ones shown in the link you posted. Now the 327 was only used up to '68 and the TRS didn't come out until '73. I'm thinking these trannys were probably used in a inboard application so they probably aren't set up for a sterndrive, TRS. Parts for the actual transmissions you get from B-W. The sterndrive tailstocks are Mercury parts. Those tailstocks are no longer availiable and when they were they were over $900 so you would need to find some used. On the trans there is a metal I.D. tag. If it is red it is a 71c or 10-17(first 4 numbers in the model number). If it is green it's a 72c or 10-18. The model number will be the top number on the metal plate.Below it to the left will be the ratio. You will need 1:1. Beings they are probably from an inboard the ratio's could be anything. You will need to find out exactly what model these trannys are. If their old inboard trannys they may be ready for rebuilds and/or the incorrect ratio. May be cheaper to find some others which already have the correct tail assembly. Theres a couple on ebay now with coolers.
A 72c.
http://cgi.ebay.com/ebaymotors/Mercr...item2556812154
And a 71c.
http://cgi.ebay.com/ebaymotors/Mercr...item2550cf4545
Theres also a Merc Trans for $650 you could get and just have a spare. I've got 3 of them but never really have had any trouble with them. I'm ready if I do though.
http://cgi.ebay.com/ebaymotors/MERCU...item19c24151af