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SP-A drive questions

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murfman

Regular Contributor
I am going to rebuild a pair of SP-A outdrives to install in my 27' Magnum. So far I have gone through the Shields, and rebuilt the trim cylinders with kits from Bill Lawerence.

As I am upping the Horsepower to 450 at the crankshaft, are there any upgrades I can do to the drives to make them more durable? As far as I know the SP drives were the last of the aquamatic series single prop outdrives and had the latest and greatest updates. I've heard stories of the Aquamatic drives being bulletproof, but everything has a weak point...

So far I know I need to check the brass split ring keepers for any deformation or expansion, is there anything else?

A couple of guys on OSO are supposedly working on an adapter to run props from those black outdrives (Don't even want to type the name lol) to allow a better selection of modern prop designs.

Thanks in advance for any words of wisdom. Murf
 
The split rings are steel, the piece they hold is brass and it's the culprit on the AQ drives. You need to get the right parts from Rick on here as I don't have any left.
 
I just had to show off my pretty shield!



I also found the newer nylon short 90 degree elbow for the coolant line on the inner side of the transom and ordered new sheaths for the shift cables. I also managed to find 2 exhaust block off plates and got them all cleaned up and powder coated as well. I am hoping to put this together looking as new and clean as possible, and hopefully reward myself with years of trouble free boating (yeah right, who am I kidding)
 
murfman said:
I am going to rebuild a pair of SP-A outdrives to install in my 27' Magnum. So far I have gone through the Shields, and rebuilt the trim cylinders with kits from Bill Lawerence.

As I am upping the Horsepower to 450 at the crankshaft, are there any upgrades I can do to the drives to make them more durable? As far as I know the SP drives were the last of the aquamatic series single prop outdrives and had the latest and greatest updates. I've heard stories of the Aquamatic drives being bulletproof, but everything has a weak point...

So far I know I need to check the brass split ring keepers for any deformation or expansion, is there anything else?

A couple of guys on OSO are supposedly working on an adapter to run props from those black outdrives (Don't even want to type the name lol) to allow a better selection of modern prop designs.

Thanks in advance for any words of wisdom. Murf
Click to expand...

Murf, the SP-A drive transmission uses the integral aluminum clamping collar/bearing box.
The "A" also uses a crush sleeve or pre-tention sleeve for rolling torque value control, instead of the shims within the seal surface washer.
The "A" transmission should also be fitted with the steel split ring keeper. If not.... I sell stress proof steel keepers.

With this much power, I would:
... pull the main drive gear bearing box
... remove the universal shaft male yoke cap screw
... remove the drive shaft assembly
... push the gear from the bearings

This will allow you to examine the AFT most 31307 bearing outer race and the roller cage.
This bearing takes quite a load, and you'll want this to be in excellent condition for this much power.


NOTE:
When doing the above, a new rolling torque value must be taken and/or adjusted for.
The crush sleeve/pre-tention sleeve will be replaced... unless you have extensive experience and know how to circumvent this.

Also check the up/down movement of the transmission's vertical shaft.



.
 
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