2 Blade prop?

[lonemust]

Hi folks.. I have a 1970 starcraft v180, w/140hp merc and merc 1 outdrive.. I currently am running a 14.5 x 23 prop(3 blade). my rpms only get to 3900-4000. And it runns about 35 mph.. My question is what difference would it make if i put on a 14x19 2 blade prop.. or should i find a 14.5x19 or 21 3 blade? I want a little better hole shot and to bring the rpms up to 4200 -4600 range.. when fully loaded i have about 11oo lbs in the boat.. wife and kids like to tube.. the prop i currently run does fine and will get them going 35mph and rpms to 3900. but it doesnt matter if im pulling the tube or not, thats all it will do.. thanks

 

[lonemust]

Re: 2 Blade prop?

i would really like to know what a 2 blade prop will do as compared to the 3 blade im running now.. Please help me out here..

 

[lonemust]

Got Question on a MC-1

Got Question on a MC-1

I asked this in the forum for props, but no answers.. I have a starcraft v180, 140hp merc w/MC-1 outdrive.. I am currently running a 14.5 x 23 prop.. I found a 14 or 14.5x19 prop.. the problem in the the one i found is a 2 blade prop and i have a 3blade..

What will a 2 blade prop do if I put it on? Would it be ok to use the 2 blade prop?

The reason I ask is because my engine will only get to 3900-4000 rpm and the boat will only reach about 35mph.. I want a little better holeshot and get the enigine up between 4200-4600 rpms where it should be.. If I trim out it seems to cavitate until I trim back in.. other then not getting up to 4200-4600 rpms the boat does fine..

I know if i could find a good 14.5x19 or even a 14.5x21 it will raise the rpms. Im just curious what the 2 blade will do for me if anthing..

With everyone one in the boat(4 adults and 1 teen, noone under 200lbs) it takes a few to get on plane and it doesnt matter if Im pulling the tube or just cruising around. It preforms about the same either way..

Would like more top end but need the holeshot for the tubing..

 

[Bondo]

Re: 2 Blade prop?

Ayuh,... All ya can do is Try it....

Btw,... 2 blade props are antiques...

 

[Bondo]

Re: Got Question on a MC-1

Re: Got Question on a MC-1

Ayuh,... Try it,....
The number of blades don't mean so much as the pitch...

 

[ziggy]

Re: Got Question on a MC-1

Re: Got Question on a MC-1

for sure do something. get your rpms up. your hurting your engine (imho) being overproped. not being able to reach wot spec.

 

[lonemust]

Re: Got Question on a MC-1

Re: Got Question on a MC-1

i will put it on and see what happens.. we are taking the boat out tomorrow and i want it to do better on taking off.. I wil take the 23p with me to be safe. will let you guys know after i get home.

 

[ufm82]

Re: 2 Blade prop?

Buy the 19 pitch prop- 3 blade. Where can you even find a 2 blade of that size??? You'll see better rpm numbers, better power on the hole shot and probably not much drop in speed since you'll be raising your rpm. If you go aluminum $100 should get it done.

 

[Bamaman1]

Re: Got Question on a MC-1

Re: Got Question on a MC-1

A 140 hp I/O generally won't handle a 23 pitch prop the way they're geared. If you're lightly loaded, the 21 pitch would be the best choice. If you carry a bunch of heavyweights and/or do a lot of skiing/tubing, the 19 pitch would probably be the way to go.

 

[Don S]

Re: Got Question on a MC-1

Re: Got Question on a MC-1

I merged you two posts together and left it in the prop forum. Just because you don't receive an answer in 2 hours in the late evening, give it some time, and do not post the same thing in two different forums.

 

[lonemust]

Re: Got Question on a MC-1

Re: Got Question on a MC-1

ok thats don.. i was told by a marina that the 2 blade( which is for a mc 80) could over rev the engine and lose some on the hole shot..

The best i can figure on wieght in the boat is arond 1000-1100lbs..

thanks for the info

 

[Faztbullet]

Re: Got Question on a MC-1

Re: Got Question on a MC-1

A 2 blade is for a light hull and is often called a "speed" prop and is more effecient than a 3 blade but has more vibration..

 

[cdn-pk]

Re: Got Question on a MC-1

Re: Got Question on a MC-1

if you look at the math... theoretically a one blade prop is the best.... just in the real world it does not work. a two blade will increase vibration and usually have a larger diameter to help offset the reduced area. with a three blade the extra blade gives more surface area so the diameter is usually reduced.

i agree with ziggy IMHO you should try a 19p 3 blade..... i gotta have that fast holeshot.

 

[lonemust]

Re: Got Question on a MC-1

Re: Got Question on a MC-1

well i didnt run the 2 blade because of the vibration issue it could cause. the airguage speedo showed about 35mph while depthfinder/fishfinder showed 38.8 mph.. so that tells me my speedo is off. My tach maybe off too. the one that was on it when i bought the boat had a power wire and the wire from the coil.. the engine didnt sound right all along. so yesterday i switched it out with a tach that only has the wire from the coil going to it.. fired it up on the hose and the engine sounded better and reved up better.. wife wants to go out again tomorrow fishing so i wil see if that makes a difference.. I'm still looking for a good used 3blade 14.5x19 or 21p.. just to be safe.. i might go with a 4blade 14.5x21 if that would be right for the holeshot and keep or better my speed..

 

[lonemust]

Re: Got Question on a MC-1

Re: Got Question on a MC-1

OK.. put the 2 blade on this morning and went fishing.. 2 blade not a good idea at all.. 140hp merc is way to much power for it.. i could not rev the engine up to get on plane.. anything over 2500 rpm and i had MAJOR slippage.. so once i got to our spot to fish, I tilted the od all the way up and sat on it to change back to my 14.5x23 3 blade.. boat and I was much happier.. Thanks for everyones opinions of the subject

 

[lonemust]

Re: Got Question on a MC-1

Re: Got Question on a MC-1

Oh and once the depth/fish finder decided to work, it showed me running 42.8 mph and the tach was showing 43-4400rpm this time. I replaced the tach after orignal post( last saturday)