Swaping over from OMC to Mercruiser

starsnstripers

starsnstripers

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Anyone have or know where on the site here i can get the Mercruiser Measurements/specs/schematics for the engine mount bed/stringer measurements height-distance from outside of transom? Transome thickness? Bottom of opening to bottom of boat? etc? I have the Mercruiser hole pattern, I just need the height and engine mount base measurements. Thanks for any help. Oh, this will be for a 5.7 mercruiser engine prealpha/alpha 80ish thanks
 
starsnstripers

starsnstripers

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Re: Swaping over from OMC to Mercruiser

The OMC WAS a stringer, i'm closing in the transom and installing a Mercruiser set up. 1972 SS-215 hardtop Slickcraft. The eng. mount bolt holes are 22" oc across from stringer to stringer on the doner boat that had a mercruiser in it. My stringers are 20" inside from stringer to stringer. Dont know if i have enough room or need to build the emg bed stringers out some? I have pre Alpha manuals i'll see if i can find the specs in there thanks
 
Don S

Don S

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Re: Swaping over from OMC to Mercruiser

The only thing you can do is install the transom shield per specs. Then set the engine on the rear mounts and bolt them down. Then lift the front of the engine so the alignment bar goes in all the way. Not perfect, but close
Now make some measurements for adjusting the pads on the stringers.
I do this all the time,
 
starsnstripers

starsnstripers

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Re: Swaping over from OMC to Mercruiser

I can do that Don where can i get the cutout specs? The donor boat had the bottom of the cutout 5 3/4" up from bottom of boat. I'd like to get the cut out somewhat close to where i need to be on the stringers. Dont want it to low and have to trim the top of stringers.
 
Bondo

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Re: Swaping over from OMC to Mercruiser

Ayuh,... I've always pretty much done as Don says,...

Glass in the Hole at 2" thick,.. True, Flat,+ Parallel...
Decide exactly where you want the crankshaft/ propshafts to live,...
Cut the new hole,+ do the transom assembley,...
Then hang the motor, with it's steel motor mounts off a crane,+ slide in the alignment bar,...
Then mock-up,+ build the boat's motor mounts to Match....
I have the Mercruiser hole pattern,
Click to expand...

Figure out,+ Mark the center for the Crankshaft on the pattern,...2 Lines,.. up, down,+ Across...
Then you'll know where the Propshaft will be...;)
Alpha's are 21, 13/16" between them... Anti-cav plate is 8" above the propshaft....



Btw,... Reading the post that Wasn't there,...
Every Hull is different,....
1 rule of thumb is,... The Anti-cav plate at the level of the Keel Line...

Personally,... I think that's alittle Deep for most hulls,...
But it's a decision that You have to make...
 
Don S

Don S

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Re: Swaping over from OMC to Mercruiser

Here is a link to a 2001 installation manual. It will give you the X dimension which is how the Center line for the crankshaft is determined. You need to forget about the front mounts. Get the cutout in the correct location, then figure out where the front mounts go. DO NOT try to do it in reverse. If you have to cut the front mounts down, so be it. Life in the outdrive world. The front mounts are secondary to cutout location.

http://www.boatfix.com/merc/Install/gas/86017211.pdf
 
starsnstripers

starsnstripers

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Re: Swaping over from OMC to Mercruiser

21 13/16 betweem what? the eng mount holes? Without the engine and drive on the boat how do you determine where the crankshaft center is? What should the measurement be from the keel line to the bottom of the cutout? OR whats the measurement from the cav plate to the crank center?
 
Zackman

Zackman

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Re: Swaping over from OMC to Mercruiser

Look at pages 10 - 15 in the document Mr. Don posted. As I understand it, everything is based on the "X" dimension.​
 
starsnstripers

starsnstripers

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Re: Swaping over from OMC to Mercruiser

Thanks Don / Zack that should do it nicely. This should be fun! :D
 
starsnstripers

starsnstripers

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Re: Swaping over from OMC to Mercruiser

I'm looking Zack Should be able to do this project now. "should" LOL will keep ya posted thanks again guys
 
Don S

Don S

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Re: Swaping over from OMC to Mercruiser

Just thought of something, the cutout for the VP SX/DP-S drive is exactly the same as a Merc Alpha cutout. But the location of the X dimension is EXACTLY the same. Center line of the crankshaft of the engine. So here is a VP transom cutout template that you can actually buy full sized if you want so you can locate it to the Merc dimentiions.
 
starsnstripers

starsnstripers

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Re: Swaping over from OMC to Mercruiser

Got it Don I'll be sure to do the cutout first. So, the center of template and center of crankshaft should be 13 9/16 up from transom line if i read the diagrams correctly. Using the square method.
 
O

oldsub86

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Re: Swaping over from OMC to Mercruiser

I hope you are taking lots of photos and will post in due course.

I will likly have to do the same one day.

Randy
 
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