proper prop 82 merc 90

[dw711]

just wondering which props i should have.I have an 82 merc 90 hangin on an 87' thundercraft open bow 15'(merc is inline 6) currently running a 23 pitch prop and i would like to get one for skiing and one for playin (hole shots and top speed (short of a chopper prop) Also wondering if a fin on cavitation plate would help keep prop from cavitating in corners?<br /><br />thanks

 

[evin300]

Re: proper prop 82 merc 90

My guess would be a high rake 3-blade for top speed, and a 4 or 5 blade for ski & holeshot, probably a 4-blade would be a good compromise. With the right prop you wont cavitate in the corners. The fin may help a little, but engine hieght and the correct prop will solve that problem. The better the prop the higher you can mount the engine.

 

[kevlar3000]

Re: proper prop 82 merc 90

23 sounds like a lot of pitch to me on a 15 ft w/a 90 hp. Do you have a tach? My memory says that should be in the 4500 to 5000 rpm range, check the Merc book to make sure. Staying in that range is important. I have usually ran into folks that run 17 to 19 pitch for skiing, and 21 for speed. Check those rpms.... And enjoy!!!!

 

[evin300]

Re: proper prop 82 merc 90

I agree, That prop sounds too big. And could be causing some cavitation. Would be nice if you knew the RPM and MPH at top speed.

 

[dw711]

Re: proper prop 82 merc 90

i'm replying to my own topic because thats the only way your replies will come up on my screen. thnks

 

[dw711]

Re: proper prop 82 merc 90

thanks guys. I run about 50mph by myself and inbetween 4400 and 4800 on the tach. Motor is mounted as low as it can go and cav. plate is about an inch above bottom of boat. With a load in the boat(2to 4 adults)I run about 42 mph and motor does'nt cavitate if i can keep two people in the back seats but alone or with one other person with me i have to back way off the throttle to make turns(not sharp ones either)<br />Thanks dw