Need help picking prop

[10 FOOT INVADER]

Bent up and chipped a blade on my prop. 3 Blade 48 832830a45 19p. Boat is a 1994 monterey 206scr with a 305 mercruiser 190 hp alpha1 gen 2 outdrive. My top speed fully loaded with gas 4 kids wife myself and brother in law and all coolers around 42mph at 4800 rpm. RPM is high. What would be a good size prop for load and speed for this boat. Not looking for speed boat speed just good all around performance. Thanks, Robert. Boat had a extra prop in it. A 4 blade. Put it on to get back on the water. It ran the same speed 42mph gps at 4800 rpm. But with the 4 blade would jump out of the water onto plane. Also with the 4 blade used a lot more fuel. I do not see any id numbers on the 4 blade prop. But she would stay on plane at lower speeds with the 4 blade. Found this number on back of prop. 14.5x19p

 

[drivehard]

Re: Need help picking prop

I think the RPM's for that motor are 4200-4600, so you are a bit above the suggested RPM's.

If you run loaded most of the time, and can control your RPM's at top speed, I would stay with what you got size wise. You could try switching to SS and see if you get a few mph's and maybe drop some RPM's

If you run empty most of the time, I would step up a pitch size to a 21P prop. That should improve your economy a bit, and get the engine down the the proper RPM level at full throttle.

I had a 190hp 305 in my 20' Bayliner. It had a 21P SS prop. At full throttle with just my wife on board we would run 52-53 mph right at 4600 rpm. Just an FYI.

 

[Tail_Gunner]

Re: Need help picking prop

Bent up and chipped a blade on my prop. 3 Blade 48 832830a45 19p. Boat is a 1994 monterey 206scr with a 305 mercruiser 190 hp alpha1 gen 2 outdrive. My top speed fully loaded with gas 4 kids wife myself and brother in law and all coolers around 42mph at 4800 rpm. RPM is high. What would be a good size prop for load and speed for this boat. Not looking for speed boat speed just good all around performance. Thanks, Robert. Boat had a extra prop in it. A 4 blade. Put it on to get back on the water. It ran the same speed 42mph gps at 4800 rpm. But with the 4 blade would jump out of the water onto plane. Also with the 4 blade used a lot more fuel. I do not see any id numbers on the 4 blade prop. But she would stay on plane at lower speeds with the 4 blade. Found this number on back of prop. 14.5x19p

If you consistenly run with much much weight on board id say your about dead on in prop pitch, but i suspect your a bit under propped ..do you want a SS prop or alum....But your fuel econ going down is a bit puzzling...but if your under propped it might make some sense...

is your tach correct...aka you might be running much higher rpm than indicated..you have run a 3 blade damaged prop @ the same rpm as a 4 blade you should have lost 200-400 rpm something's missing.. Check you tach

But a boat that big and that much weight id consider a SS prop it will have much less deformation under high loads and be more efficent

 

[10 FOOT INVADER]

Re: Need help picking prop

The boats is always loaded. 4 kids and all the toys and coolers. At 42mph gps fully loaded with a 190hp 305 I dont think I can complain. Its a big heavy boat. The only difference from the three blade to the four blade I could see was, the boat would come out of the hole really quick. I would go full throttle and would have to start backing down the throttle quick. It would ride a lot smoother and stay on plane at slower speeds.Top speed still at 42mph gps at 4800 rpms. I would like to get the rpms down to around 4400. Have checked rpms with my digital tac meter. If I hold it wide open the rpms will go to 5000.I try to keep it uder 4400 at full throttle. I mostly cruise around at 3000 rpms at about 25-28 mph. Would like to find a good 3 blade prop to keep rpms around 4400-4600 wot. I have good throttle controll but others who might drive the boat may not. Thanks Robert.

 

[Tail_Gunner]

Re: Need help picking prop

Well 5000 rpm with a 19p 4 blade. lets drop the 4th blade and add 100 rpm netting 5100 as a 3blade in a 19 pitch alum

All 3 bladed prop's

5100 W/19p
4900 w/20p
4700 w/21p *
4500 w/22p

The apollo prop's would be a very good choice.

http://boatpropellers.iboats.com/Me...andard&**********=576848948&*******=314612055


http://boatpropellers.iboats.com/Me...andard&**********=576848948&*******=314612055


I truly believe that you are under propped even with the above number's, When finding the right prop or gearing it is generally accecepted to run a boat at to it's max rpm ..it would be intresting to just add increased pitched props to you boat until the rpm falls down to 4700...that would be the right pitch..But with that said that 20p 4 blade should give max econ and lower planing speed's and a better hole shot..

Got any friends that will loan you a 21p 3 blade for a day..

 

[10 FOOT INVADER]

Re: Need help picking prop

Thanks. I am going to order the 4 blade prop. That should put the rpm at the right rpm. The couple I bought the boat from only used it to ride around the lake. Never really pushed it much.