Alpha transom dimension?

wire2 · Aug 9, 2007

I'm ready to cut the hole for the transom assembly to fit an alpha gen 2 outdrive.
I placed the outdrive into the transom assembly on my bench today to get a height. With a straight edge extending down from the cavitation plate, I measure 3-3/4" to the bottom edge of the transom assembly, (not counting trim parts)

Would someone please confirm that's a valid measurement from the "V" of the hull to the lower edge of the assembly?
Thanks

ps, I went to Mercury Marine in Ontario yesterday, tried to get a part # for the template they used to include with every new I/O, apparently they haven't used them for several years. The dealers use a metal jig now, I'm told.

95yj · Aug 9, 2007

Re: Alpha transom dimension?

I may be way off here, but wouldn't the transom assembly need to be lined up with the height of the engine and not necessarily a certain height from the bottom of the hull?

On my boat the measurement from the cavitation plate is 4.5 inches to the bottom of the hull or 5 inches from the bottom of the gimbal housing to the bottom of the hull.

wire2 · Aug 9, 2007

Re: Alpha transom dimension?

Thanks for the reply, YJ.

That's kind of putting the cart in front of the horse. The cavitation plate must be level with the lowest part of the hull, so the outdrive decides the transom assembly height, the inner transom plate decides the engine height.

95yj · Aug 9, 2007

Re: Alpha transom dimension?

I agree on that, but there's a little room for playing around and I would probably not want to have to change the height of my front motor mounts if it wasn't actually necessary.

wire2 · Aug 9, 2007

Re: Alpha transom dimension?

It's actually necessary.

I removed an OMC 800 stringer system, am now installing alpha gen 2, re-using only the 5.7 and ss headers. So engine will go where it needs to.

I just want to avoid drilling more than 1 set of holes in the transom to have cavitation plate level with hull "V".

95yj · Aug 9, 2007

Re: Alpha transom dimension?

Point taken.

On the other note, drilling hole in the transom or bottom of the boat is scary. Measure twice cut once doesn't apply. I measure about fifty times, mark it off and then go think about it for a while. It's like when you were a kid cutting into the hood of your first car to put the scoop on except the car doesn't wind up in the bottom of the bay when you screw up.

wire2 · Aug 10, 2007

Re: Alpha transom dimension?

I hadn't considered it before, but the transom angle affects the transom assembly to hull dimension. (Geometry class was a loooong time ago).
I found a template on page 15 here; http://www.boatfix.com/merc/Install/gas/86017211.pdf
But it references to a point *somewhere* between the bolt holes.
The template is obsolete, does anyone have one (or the metal fixture) to measure the vertical distance between the reference point and the bolts just below? Thanks.

Bondo · Aug 10, 2007

Re: Alpha transom dimension?

But it references to a point *somewhere* between the bolt holes.

That point Somewhere is the Crankshaft Center Line..........
And the template I see in the link you posted is Current, not Obsolete......

It's explained on How to find the Crankshaft Center Line in the manual in the link......

wire2 · Aug 10, 2007

Re: Alpha transom dimension?

Bond-o said:
That point Somewhere is the Crankshaft Center Line..........
And the template I see in the link you posted is Current, not Obsolete......

It's explained on How to find the Crankshaft Center Line in the manual in the link......

Ok, thanks, I suppose that makes sense.
But as I see it, I need to establish that point on the transom first, to get the cavitation plate height. Then I adjust motor mounts to coincide, and test with alignment tool. Or am I missing the forest for the trees?
When I said it was obsolete, wrong word. I should have said, no longer available. The people at the Mercury office/warehouse in Ontario tell me it hasn't been available for 10 years. I called a large dealer in Toronto, gave them the number on the template in case they carried some old stock; nope.

wire2 · Aug 10, 2007

Re: Alpha transom dimension?

I measured my transom angle today, it's 14?, so my X dimension is 14-3/16" by the chart. I have it marked on my transom.
I read the whole section again, I don't see a reference to how far down, (or up) it is to the nearest bolts to drill. If someone would point it out to me in that section, I'll gladly admit that you're smarter than I.

Don S · Aug 10, 2007

Re: Alpha transom dimension?

There isn't any reference to the nearest bolt. On the drill jig is a scribed line for the X dimension (Crankshaft Center Line), both vertical and horizontal. The chart is not available anymore from Merc, you need to get the drill jig.
Now, if I can find the number again, and you have a Volvo Penta dealer nearby, they have the exact same cutout on the SX and DPS drives. The centerline of the crank is the same, because the Volvo SX/DPS can use a Merc cutout and the cavitation plate is perfect.

wire2 · Aug 10, 2007

Re: Alpha transom dimension?

Ok, I'll try the local dealers. I'll bring a large sheet of paper & make one from their jig. And note the missing dimension.
Thanks.

Reel Poor · Aug 10, 2007

Re: Alpha transom dimension?

On the Volvo Penta SX chart the 14 degree transom X-dimension is 14-1/64 inch. The cut-out template is part #3850029 and the transom shield instalation instruction booklet is part #3858039. I think the kit part number is 3858044.

wire2 · Aug 11, 2007

Re: Alpha transom dimension?

Ok, I knew there had to be a way.

I kept blowing up the drawing until a print matched 2 bolt centers perfectly, then measured to the line.

Woohoo!

wire2 · Aug 12, 2007

Re: Alpha transom dimension?

Reel Poor said:
On the Volvo Penta SX chart the 14 degree transom X-dimension is 14-1/64 inch. The cut-out template is part #3850029 and the transom shield instalation instruction booklet is part #3858039. I think the kit part number is 3858044.

Ok, thanks, Reel. I just tonight noticed you'd given me the info when I looked at the posts again. My bad.

I haven't looked in the yellow pages for a Volvo dealer yet but I will try to locate one, I'd like to get the booklet, at least.

The Merc chart says 14-3/16, only 11/64 more, but then the write up says it can be increased up to 2?", so there's obviously room to experiment.

I blew up the drawing on the Merc site, then printed it in 4 quarters, so I now have a full size template.

YJ, you told me 5" from your transom assembly to hull bottom; that's exactly what I get with this template. (A good sign). I expect your transom is also 14??

One last question, (for now), the hole saw drilling for the steering lever looks to 1-3/4" diameter, angled 30? to the left & right, close enough?

Reel Poor · Aug 12, 2007

Re: Alpha transom dimension?

You have a PM.

Alpha transom dimension?

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