Prop Suggestions

[markheck1]

Had the old girl out today, runs good

1984 Chris Craft Scorpion, 186 BR, with an all original as far as I can tell 198HP 898 in front of an MR drive spinning a 14.5 x 17 wheel that's got a few dings in it.....NADA lists her at 1550 but I suspect this might be a bit low....

39 on the GPS at a little over 4000 RPMS, trimmed all the way out....
pulls skiers up without a ton of bow rise, a little more than I would like possibly, but not unbearable....might do smart tabs this winter, have a really old set of small spring loaded ones on it now, and they helped
boat runs great until you dig hard into a turn, then for lack of a better term it blows out, and starts slipping, yank the throttle back to idle let it settle a sec, and hit hard again, and no slip, just hard at speed in turns. This may just be how this hull performs, I don't know.

Don't really do a whole lot of cruising, mostly tubing and playing......

2 questions,
1 how is this prop performing with this boat.

2 looking for suggestions for a new prop, again just for mostly play.....
thinking of a 4 bladed, good idea? bad Idea
Kinda looking for something to hold the turns better maybe

THANKS FOR ANY SUGGESTIONS!!

 

[steelespike]

Re: Prop Suggestions

I wasn't able to find a 898 or MR drive.? Infact you may know more than I've been able to find about your setup.
I'm assuming an OMC. with a 1.50 gear ratio and a 3.8 motor.I also couldn't find a 198 hp.
Your gear ratio may be on the out drive. 1550 sounds more like a outboard dry weight.
Assuming the info I found is correct your doing pretty well Max rpm for the motor is 4200 I'm assuming a little over 4000 is 4100.
39 gps indicates about 11% slip, seems reasonable.
Usually you would need to trim down for a hard turn and ventilation may be worse in one direction than the other.
It would be interesting to see your wot speed with the tabs fully retracted.
As far as a prop change It seems your pretty close right now.
A 16" 4 blade may improve your hole shot and reduce the venting.May stay on plane better at reduced throttle
and may handle better around the dock.But odds are it will reduce your top speed.

 

[markheck1]

Re: Prop Suggestions

Thanks for the reply, ...
It's a Mercruiser, not an OMC.....I guess it would be called an early Alpha......
198HP 898 is a stock 305 Chevy 2BBL I had the serial number somewhere but can't find it at the moment,
as far as the weight, I was thinking she's more like 2500, definitely feel her on the trailer.....

I forgot to mention that I don't normally trim up at all while towing, it's not a huge deal, it's when I drop a skiier or tuber, and crank it around to get back and protect them fast. If i just crank the wheel and don't slow way down, it happens....
The tabs are pretty small, around 3 Inches by 6 inches, and spring loaded, but I will say that I can't remember any difference in the top speed before and after....

Again, thanks for the reply

 

[markheck1]

Re: Prop Suggestions

Serial Number is 0B585240 I don't see gear ratio marked anywhere
and the prop is 48-78118-a40 17P
Dangit, I was gonna take a pic of the tabs.

 

[markheck1]

Re: Prop Suggestions

Can't find gear ratio, chart only lists 200 which would be 1.65 to 1....how much does this change the data?

There is a Large F stamped in the side near the serial number if that helps.

THANKS!

 

[steelespike]

Re: Prop Suggestions

I found a 898 in 82 with a 1.70 gear ratio. You can't do 39 at 4100 4200 is a really low 2% not likely.
But this just means your tach is probably reading a little low.
A 4 blade 16" pitch prop should maintain your rpm get out of the hole quicker with less bow rise,should grip better in a turn
and respond better around the dock.I don't know if you can find a 16". Solas props have a good reputation.

 

[jestor68]

Re: Prop Suggestions

Because you need to bring your WOT rpm up a little, I recommend a Solas Rubex 4 blade 14-4/5 X 15 (aluminum) prop.

This prop will provide good, strong acceleration for water sports and great grip in turns.

If you want to spend the extra $, the Solas SS versions will work even better due to their extra cupping.

 

[markheck1]

Re: Prop Suggestions

It's possible the tach is reading low, I'll have to take the shop tach out and verify it,


THANKS for the recommendations