Prop Help ?
 

Hi guys, I have a 34' Magic Sorcerer.
Last summer I destroyed a Bravo 1. Since then, I have replaced lowers w/ Imco 2" shortys. Boat used to run 80-82 mph @5200. Trimmed, bow would ride nice and dance a little in the wind, very stable. Now w/shortys, props slip a little getting on plane. (which I expected) Problem is, I can't get bow up and trimmed and I lost about 6mph. I'm going to try 1":cool-smiley-011: spacers but didn't know if this is something props or changing rotation would fix?
Thanks for any help,
Darren

I have a 32' AT with Stellings extension boxes. With the stock length Merc lowers (no nose cones) my the propshaft centerline sat about 3.5-4.0 inches below the hull and the boat would run up to about 86-88mph with full fuel, but would sometimes begin to do a severe chine walk after about 80+mph in calm seas as I would trim up....installed a pair of IMCO -2" lowers and with lab finished 32" 4-bladed Bravo One props the boat had a very hard time getting on plane....had to find the sweet spot, but noticed that the -2 IMCO's gave a much flatter ride and boat sat up on top of the water much better.....better angle of attack, better handling, and no chine walk. I think it is because my boat was stern heavy with the extension boxes and all, but the -2 shorties helped level it out with a different angle of attack, but I still needed some 5-bladed props to get the boat on plane. So, I added some 5-bladed P5X's retained the same RPM and hit 93.7mph on the GPS.

My boat acts like a whole different boat now with the -2 shorties.

Basically, Chine Walk usually begins as the boat approaches higher speeds and is when the hull cannot stabilize itself for one reason or another and rocks/bounces from the port to starboard chines of the hull. It can become very violent very quickly. How the hull rides in the water has a lot to do with it-----and my boat was a bit stern heavy.

I hate when this happens. I wrote 6 paragraphs and it didn't load to the forum.!!!!!!!!!!!

KAAMA, your numbers are more than can be expected in most situations. Decreasing the prop depth flattened the boat because the tail lift decreased wetting the keel allowing you to be able to drive your boat. It is unusual the wetted hull drag was more efficiant than the drive drag. 7 mph was a almost unbelievable increase. Good for you!

M1, try the spacer, I think it is the right way to go. You'll get on plane easier and have trim reaction. If you want to test some props, let us know.

Brett, I appreciate your input...yes, I was very surprised myself, but the only thing I do not like about going with the -2shorties is that I lost about 5-6mph in my mid range cruising speeds which I am very dissappointed about!!!. My P5X's are 30" non labbed props that I am currently using with the -2 IMCO's. I was using a Merc Bravo One 32" 4-bladed prop with the standard length Bravo One lowers (no nose cones). Besides doing a very poor job of planning my boat off, the 32" labbed Bravo One props originally killed the midrange cruising speeds by about 10mph with the -2" IMCO shorties......while the 30" P5X's gave back about 4-5mph of of the 10mph lost.


I wanted to conduct a test while cruising steady at 3800rpm...I would trim the drives up and down to see if there were any speed differences. The GPS showed about 1/2mph increase in speed as I trimmed the drives DOWN to the nuetral position or the next higher number in the trim position. I also did this at 4500rpm...same results. I did this without readjusting the throttle position...which actually would bring my RPM's down by about 100-200rpm's or so. So, I was actually going faster with less RPM and less trim. However, some guys told me that it wasn't really a fair test at mid range cruising speeds.....they think my boat will still go faster with the higher trim position at WOT vs the lower trim position. It's really a very difficult test to conduct at WOT because my hands are full at those speeds.

So, all I know is that I would really like to get back the 5-6mph I am missing from my midrange cruising speeds (if I can) without killing the top end speed.
I do not want a spacer....If I cannot fix the problem with the correct prop, then I will just accept it as it is! Any ideas???

Magic1---not trying to "hi-jack" your thread...I am just responding to Brett/BBlades comments. I think anyone can glean info from the trial and errors of others---especially mine! :o

Not a problem Kaama,
I'm just takin all this in. The more info the better!
Just finished fillin drives with lube, hope'n to run it with new
1" spacers this weekend. I'll let you know how she does.
Are you guys ok with Mercs high perf. lube in drives?
Someone refered to it as "green death".
Kinda scared me, thats all I've ever run.

Hey Kaama,
Did going to 5 blade props get you up on plane better?

KAAMA,

You lost 10 mph at mid going to the shorties and only gained 5 back with the 5 blades. Is that OK with you? Top end was the gain and if that is the goal, so be it. There is most often give and take. A spacer will be the better of both worlds although you don't want to hear that.

Majic1, I'm sure the 5 blades helped planning compared to the 4 blade at either setting. Merc oil is absolutly fine.

With the -2" IMCO shorties....Yes, the 5-blades did an excellent job of popping my boat up on plane......the 4-blades could hardly get me up on plane...they were a nightmare!

[QUOTE=bbladesprops;2434504]KAAMA,

You lost 10 mph at mid going to the shorties and only gained 5 back with the 5 blades. Is that OK with you? Top end was the gain and if that is the goal, so be it. There is most often give and take. A spacer will be the better of both worlds although you don't want to hear that. [QUOTE]

With going to the shorties, I lost 10mph in mid range cruising speeds using the 32" 4-bladed Bravo One labbed props.

Then I tried the 28" P5X 5-bladed props....with 8-9mph loss in the midrange, but I gained about 2-3mph at WOT.

Then I tried the 30" P5X 5-bladed props....midrange cruising speed saw about 5-6mph loss in midrange.

I wonder if a pair of 32" P5X's will put me back to the midrange cruising speeds I once had or at least much closer to it, but I will have to bump up the power in my engines to turn those 32" P5X's.