TRS X Dimension - help please
 

G'day all,

Stumbled across this board looking for TRS drive specs and was astounded by the amount of good info here.

I have a question about rigging a TRS drive on a 21ft Connely V hull ski/runabout. First a few details that might help:

1) I know most posts relate to "real" offshore boats but you all seemed pretty helpful so I thought I would ask.

2) The Connelly is an Australian made hull originally designed as a rough water ski hull. They were usually setup with Blown BBCs & SSMs or twin rig outboards and have around 24 degrees of deadrise so can carry some weight in the tail. There is no planing pad or step in the hull.

3) I know the TRS is way too much (heavy) drive for this hull but the price for the complete setup ( 280 TRS) with about 30 hours total was less than half of what a secondhand Bravo (drive only) costs over here. Included in the deal were three Laser IIs, a 19", 21", 23" and a complete set of Mercruiser manuals for the drive and motor.

How far below the transom base should the prop centerline be? I am more interessted in getting out of the hole than absolute top speed as I don't have a lot of HP anyway. Putting the question another way. How low can can I set the drive and not lose too much off the top end as I do not have a lot of transom height to play with.

Appreciate any help I can get.

Connelly21

There were not many single engine TRS setups, so it's kind of difficult to answer. I think there was a 27 Excalibur made in the late 70s, early 80s that used a single TRS. You may want to check that forum for info on drive height.
Gary

You have to be a gold or platinum member to post in the owners forum, so you might want to check for somebodies name in the Excalibur section and email them.
DS

I used to have a 24' Superboat with a single TRS.

You could ask them

i have a 28 cig open with a single trs left hand drive . the propshaft is at the center or even with the keel. carves turns like a ginsu knife:D

Thank's for the replies. I chased down a few of the leads and consensus seems to agree with open72.

Connelly 21; Sorry to be so slow getting to you but I had to get into the storage spot to get some measurements. I have a 25' 1977 Martini with a 24 deg. "V" that came new with a TRS and Merc "cleaver" style prop. The factory set-up had the cavitation plate only about an inch or so above the keel line. (I don't remember exactly, but it was way too low for today's props and I tore everything apart and raised it.) I can't trim my unit as stored to give you the exact prop shaft center to keel line # but going about it another way ... the vertical distance from the drive input C/L to the extended keel line is 18 1/2 inches. I would estimate that would put the prop shaft C/L a couple inches below the keel line when parallel. I now have some minor cavitation on hard left turns and need to trim in to avoid it. (using 3bl Mirage and 4bl Spinelli) Considering the use that you wish to put the rig to and the props that you will be starting with, I would STRONGLY recommend that you don't go higher. I can probably figure out how to convert my measurement to a propshaft/keelline # if I go back and get some more #s from my outdrive, or you can calculate it with the unit you have there. Hope this helps some. --- Jer

I have a Firefox that I bought new in 1987. It has a 24 degree bottom. Before I went with a Mercruiser #3 speedmaster, I discussed the trs drive application with Val Jenkins. He worked at Cigarette for many years and was their hands on man for just these types of procedures. A 17 1/2" X dimension was what he recommended for the trs drive in the Firefox. The X being the crankshaft centerline measured at the transom from the keel up.
Good Luck
Ed

How about posting some pics of the Firefox? I`d love to see it.

What are you running for power?

The engine is 522ci. Chevy 9.8 bowtie block, oliver billet rods, JE pistons, Air Flow Research prepared Merlin heads, port matched intake, B&M blower, Holley dominator. Charlie Weston did the machine work, I hand assembled the pieces. Huber 1450 Kryptonite trans, Mercruiser #3 speedmaster. The boat is winterized and covered, but I may have some pictures of me picking it up at the Cigarette Factory in 1987.
Ed