Cutting Transom/ Transom Angle/ New Drive questions

[AGUESS]

Hi Everyone,

I want to cut the transom in my restored 66 Classic 18 this weekend. Just got a paper transom template. Questions, need help.

1. How do you calculate the transom angle? Template shows different X Dimensions for different angles.

I would think that I can hold a level against the transom so it is plumb and then take a compass to figure the angle. Will this work?

Does anyone know the angle of a 66 Classic 18?

2. When I measure up say 14 5/8 inches for the X Dimension, I assume that I just measure from the bottom of the keel up the trnasom. Is this correct? or do I have to measure up a plumb line - like off the level, which would make the measurement higher than just going up the transom I think.

3. Once I have the X Demension figured out, what is the best tool to cut the transom with? Saws all, jig saw? I know to start with a hole saw.

As always, thanks for your help.

Alex Guess :confused:

[RickR]

Alex
I'll email OMC instructions to cut and install your transom plate. (BIG FILE)

The bottom line (true bottom) for the X-Dimension is measured from a horizontal line above the keel. The width of the horizontal line is equal to the width of the anti-ventilation plate.
Do a search on old posts on x-dimension.

When using a hole saw use drill in reverse until your through gel coat. Once you change back to forward be carefull it doesn't grab and chip the fiberglass.
Use masking tape on gel coat and jig saw bed.
Burnish screw holes.
Seal the exposed wood with epoxy.

[Scott Pearson]

Alex,
You must know the Transom Angle befor your X-Dimension. You need a Chart that shows the angle that = the Dimension. OK...so on Alphas it is as follow. Its different with Bravo's and Blackhawk's.

Transom Angle Measurement

16 Degree 14-5/16 (364mm)
15 Degree 14-1/4 (362mm)
14 Degree 14-3/16 (360mm)
13 Degree 14-1/8 (359mm)
12 Degree 14-1/16 (357mm)
11 Degree 14 (356mm)
10 Degree 13-15/16 (354mm)


Your X-Dimension should Correspond to the Transom Angle recommended from the sterndrive company.

An X-Dimension can be measured by a 90 degree tool or by Tape Measure Method.

You MUST know the Angle of the Transon and the recommended X-Dimension. Then once you have that you can raise it up or down from there. You also MUST know how far you can go up without having problems.

Alpha one... 2-1/2in. (64mm) Max
Bravo One/Two...3 in. (76mm) Max
Bravo Three...1 in. (25mm) Max
Blackhawk...NEVER more then 1-1/2 (37mm) max

I used a Sawsall to cut the transom in my boat.

(NJ)Scott

[RickR]

I know my computer graphics leave ALOT to be desired but here is how you measure a true bottom according to Merc.
http://www.donzi.net/photos/rickr03truebottom.jpg

[RickR]

Scott P
What is the "Transom Angle Measurement" for a 24 degree Deep V like the Donzi?

Do you use the the chart to correct for the "Actual Bottom"? Or do you still measure from the "True Bottom"?

[Scott Pearson]

Rick,
The "Transom Angle Measurement" Would be the measurement from the "Actual Bottom" This is taking in account the "Transom Angle". You want the exact "Crankshaft Horizontal Centerline" and "Vertical Centerline" This is your X-Dimension. In the OEM Mercruiser Manual they are going by "Actual Bottom" NOT "True Bottom" This is why they make a recomadation using the 90 Degree Tool Method. This is the easy Method and you dont have to take the Transom angle into account. This Chart is different and is as follow:

Sterndrive Unit Location

Alpha One 13-9/16 (345mm)
Bravo One/Two/Three 13-9/16 (345mm)
Blackhawk 16-1/2 (419mm)

The above would be the Stock X-Dimension.What you do with it from there is up to the installer.

I measured up from my "Actual Bottom" added 1-1/2 inch to raise the X-Dimension. If I went with the graph that you posted I think I would have had problems, Aerated drive...etc.


(NJ)Scott

[RickR]

Thanks
I did not realize "Tramsom Angle" is the fore/aft angle of the hull (not the deadrise) which on the 22 is around 10.5 degrees.

If I remember correctly the X dimension on Reddog's "Genuine Trouble" is up, 1.25" from the "True Bottom" (that was about 2.5" from actual bottom)


On the 22 X-Dimension is even with the "True Bottom"

[AGUESS]

Rick & Scott

Thank you for the continued education. Rick, the X Dimension info you scaned and sent me is great. This really helps to explain what I need to do.

I think we (donzi.net) members need to have an area on this site that shows these type of technical illustrations for everyone to use. I also think that we should have a listing of suppliers with phone numbers, web address, etc. for restoration and repair items.

Scott, thanks for yet another bit of your knowledge.

Glad to have such good friends on the donzi.net.

Alex :)

[Scott Pearson]

Alex,
Let us know how you make out :D And dont slip with the saw!!! :eek: (Kidding!)


(NJ)Scott

[GeneD]

Holy smokes Alex, you really cut your transom off?!?!?!?!?!
Geez, if need be...I will measure mine. I have a few days off...
Man, you are scaring me though!

[GeneD]

Hey guys...I am a bit delirious right now. Unlike Spitfire Dave, I had to drive to FLA straight through...been up since 7:30 AM Monday.
Re-read your post Alex. What you want to do it re-establish your X-Dimension if I read this right.
Let me measure mine, since you and I have the same type hull design.
Remind me, what type engine package are you using? Hopefully it is NOT a Volvo.
No offense to any Volvo owners out there...
But...if you want to go fast, you need a Merc drive.

[GeneD]

Well gee Scott, you must not be impressed with any of the newer high performance boats out there either huh?
Let's see, just about every boat in the APBA circuit runs a Chevy type engine, and about 75% of those boats are running Mercruisers of various sizes.
Donzi only puts Merc packages in all their I/O's (though I heard talk of a diesel soon)as do most of the world's boat manufacturers. Please don't ramble on to me about monopolies and the like, if these powerplants were no good, they would go bankrupt just like OMC did.
Granted, most of the raceboats are running BB's, but there are a few out there that run SB's too.
AND...if this isn't enough to convince you, with the exception of Chris Reindel's new boat (formerly Armada) every single outdrive boat is running a Mercury drive. Let me repeat that, ALL the race boats running an outdrive with the exception of Reindel, is running a Mercury outdrive.
Since my rebuild, I haven't had a single lick of trouble with my drive, and I beat the hell out of my boat as you well know.
Short periods of time? It doesn't take long to pass an old Volvo as long as your motor is up to snuff.
I do know guys, and so do you Scott, that have the old Volvos and Ford engines in the 18's that can't get over 60 MPH. And from what I have seen and hear, most can't do over 50 MPH.
If you continue to screw around with old technologies, you will be disappointed everytime.
If technology was no good, we would still be driving around in Model T's and flying around in Bi-planes.
I just KNOW I am going to catch a lot of flak on this one. But then, I am still delirious from the drive to FLA from Ohio.

[Greg]

My old Volvo 200 was a real workhorse, but it always felt like I was dragging an old bedspread around behind the boat.

[AGUESS]

Hi everyone,

GeneD, I hope I am not really scaring you.
No, I do not have a Merc. I went with a 1998 Volvo Cobra SX Drive. This will mate to my new Ford 351W. I hope for around 62 mph.

I spoke with Volvo and they faxed me the Installation procedures, X Dimension calculations, etc for my SX. These are just like the ones that RickR sent me for the Merc. Rick thanks again.

I also spoke with Donzi Marine Tech Support, what a great bunch of people. I have called them alot during this restoration. Thank you to all of you for your help.

Donzi Marine said that the Classic 18 has a transom angle of 12 degrees, and that they install the Volvo SX drive with an X Dimension of 14 1/2. This sounds right.

Strommer has the same drive and he said his is set at 14 5/8. According to the Volvo specs, with a 12 degree transom angle the X Dimension would be 13 15/16, but I also have to start 3/4 inch above the bottom of the boat for a SX Cobra model to allow for the anti-ventilation plate height. This would make the X Dimension 14 11/16.

I think I will go with the Donzi Marine number.


QUESTION- HELP PLEASE.

When I measure up the 14 1/2 inches. Do I just measure up from the bottom of the keel (drain plug) or do I come off the keel with a level line and then measure up from the level line the 14 1/2 inches. This is what the drawing from volvo looks like, but I don't want to do this wrong.

I will also measure from the center of my crank shaft to the top of my carb to make sure there will be clearance inside the engine hatch before I cut the transom.

Thanks for all of your help. I will do this on Saturday.

Alex. :)

[marcdups]

Alex, I would really like to come and check out your new project, I am in Raleigh and have a 16, maybe we could shoot the s%$# and tell stories, I have to hook you up with the best mechanic in the area!!
Marc

[AGUESS]

Marc, I just sent you my phone number via email. lets hook up. If you want to come by on Saturday or anytime give me a call. I hope to cut the transom Saturday.

Alex