1973 20' CC Transom woes - Page 3

hermco · #21 07-30-2011, 01:15 PM

Are you sure about those measurements?

pianewman · #22 07-30-2011, 07:03 PM

Private message sent.

pianewman · #23 09-03-2011, 08:05 AM

New transom in place. Mercury OptiMax150 Motor reset so the AC plate is exactly level with the flat of the keel.

MiragePlus 48-18278, 17p prop. Underway, top speed around 40+, 5200rpm.. At top speed, regardless how I trim it, the AC plate is buried (I can't see it, clear water) and I feel the bow is too high when trimmed properly. I'm aware that this motor is 150lbs heavier than the original motor(s) back in the mid-70s, but I expected, at full throttle, things would level out.

Any thoughts? Should I raise the motor a notch? Is this the proper prop for efficiency? I'm surprised how much lateral spray comes off the motor, at speed, unless I tilt the motor out a good bit.

Again, thanks for helping me out with this.

hermco · #24 09-03-2011, 09:02 PM

You should be able to go two holes higher.

pianewman · #25 09-03-2011, 10:02 PM

Thanks, Don. You've continued to offer me sound advice. I've just spent an hour reading the "performance" threads re: props and motor height. Wow, do I have a lot to learn!

I think I've got the correct prop, and will raise the motor. There's a Mercury tech where I've got the boat stored, and he's willing to go out with me and check things out, and will raise the motor for me, as well. I might also install the Hydro-Shield I've got sitting in the back of my truck, per Fr. Frank's advice. I've just got to get over the thought of drilling through the skeg of the "new" motor!

Once again, I'm so pleased to have all this knowledge available. Thanks, guys.

FishStretcher · #26 09-04-2011, 11:47 AM

Quote:

Thanks, Don. You've continued to offer me sound advice. I've just spent an hour reading the "performance" threads re: props and motor height. Wow, do I have a lot to learn!

I think I've got the correct prop, and will raise the motor. There's a Mercury tech where I've got the boat stored, and he's willing to go out with me and check things out, and will raise the motor for me, as well. I might also install the Hydro-Shield I've got sitting in the back of my truck, per Fr. Frank's advice. I've just got to get over the thought of drilling through the skeg of the "new" motor!

Once again, I'm so pleased to have all this knowledge available. Thanks, guys.

I am happy with my hydro-shield and it has saved my prop from damage at least once this season. I suspect that dragging it thru the water might hurt my top speed, but maybe that is offset by the fact that trim seems great, even with a 4 stroke and a kicker on a 20 footer- about 430 lb total back there. And I am only pushing it with a 100 hp outboard.

pianewman · #27 09-04-2011, 11:56 AM

What did you use to seal the holes? Does the bracket gouge the paint enough that sealant needs to be placed around the edges?
Thanks.

FishStretcher · #28 09-04-2011, 11:40 PM

Quote:

What did you use to seal the holes? Does the bracket gouge the paint enough that sealant needs to be placed around the edges?
Thanks.

I did nothing. My skeg was already lacking paint from the prior owner. Florida-style.

The button head screws and half height shear nuts are fairly low profile. I just bolted it on, making sure it flies parallel to the anti-cavitation plate, and ran with it. That is a little nerve wracking- the drilling to line it up bit.

But it is on now. I bent it a little to conform to the skeg a bit better- I made the vertical parts a tiny bit concave so the leading and trailing edges squeeze tight against the skeg. I grounded it once and it has held up well, despite the fact that the 3 screws don't look that huge. I have the size large on my 100 hp 4 stroke Yamaha, for what that is worth. And the grey matches well.

I would either paint the whole thing afterwards if you want, or you could bend the stainless bracket carefully as I described and sand or grind it to conform to the skeg nicely so it doesn't scratch. I didn't see much of a gap where I could use RTV sealant.

pianewman · #29 09-05-2011, 12:02 AM

I noticed, when I held it up to the skeg, that the curve of the bracket doesn't follow the lines of the skeg, so I'm sure the top edge would cut into the paint. I'll be sure to flatten the bracket out so it lies flush.

FishStretcher · #30 09-05-2011, 07:24 PM

Quote:

I noticed, when I held it up to the skeg, that the curve of the bracket doesn't follow the lines of the skeg, so I'm sure the top edge would cut into the paint. I'll be sure to flatten the bracket out so it lies flush.

Pics of mine installed on a previously thrashed skeg.