Went to a 4blade

[M Todd]

90 17' four winns 3.0l. I had 3 14.5x19 and went to 4 14x20. I get out the hole well but when get on plain and start triming up the prop will slip and over rev. I'm not trimed up that much. On my 3blade i could see a roster tail before over reving, this 4 blade is no where near that high before it slips. I don't understand i thought the 4 blade would have alot more bit in all ranges.

 

[ramster]

Re: Went to a 4blade

My boat does the same thing with a four blade, massive rooster tail with the 3-blade, the four blade has more stern lift bringing the prop closer to the surface at less trim angle. What brand of prop do have?

 

[steelespike]

Re: Went to a 4blade

M Todd,Welcome. What brand of prop?It sure sounds to me like your setup is wrong.
Being an I/O it should be right But:: has the transom been rebuilt or the out drive comepleately removed perhaps replaced with another.
Where does the anti ventplate(just above the prop) measure in relation to the bottom of the transom?
Ramster what boat/motor do you have?

 

[ramster]

Re: Went to a 4blade

I have a Glastron SX195 with a modified 5.7 and a volvo SX drive, with my stiletto I can shoot a massive rooster tail without really loosing any grip, with my Apollo 14X20 four blade when I over trim even a little it will just cavitate and start slowing down. Since I did my engine over I cant use the 14X20 any more I now run a 23" Stiletto that works great, 62 MPH on my speedo at 4900 RPM with five people on board. A little improvement over the 5.0 2bbl. which would struggle to hit 50 with that load.

 

[steelespike]

Re: Went to a 4blade

I think its no surprise the 2 props are intended for different purposes.
the Apollo for low to mid range operation.The Stiletto for high speed operation.

 

[M Todd]

Re: Went to a 4blade

What would my 3.0l GM OMC sterndrive do if i went to a 3 blade 14.5 x 17p. Would my RMPs be to high WOT. I had a 19p and i was at like 4500 WOT on the boat tac. I run up and down the lake WOT all the time i don't want to damage anything but i would like to get 45mph out of my little boat. I can do like 37mph@4000 with my 4blade but it will pull well, 40mph@4500 with a 14.5 x 19p. Would the drop in pitch be a better prop for hole shot and top in? My 4 blade is a quicksilver, i know its a mercury product. I like the flo ll hubs in this props, i can change props with same hub.

 

[craze1cars]

Re: Went to a 4blade

Yes a drop in pitch (with your current 4,000 4 blade) will definitely get you better hole shot, and MIGHT get you 1-2 mph more top end.

I find it highly unlikely you will EVER see 45 mph wtih that 3.0L engine in your boat. With any prop. Not enough HP for your particular hull...period.

Frankly that 3 blade 19 you are running sounds very good for your application.

All things being equal, usually a 4 blade will accellerate faster than a 3 blade, but a 4 blade will be slower than a 3 blade on top speed. Since you seem to put priority on top speed, I think shopping for performance 3 blades would be better for you.

You haven't shared brand, model, material of these props you're trying. Also makes a big difference.

But a 3.0L is a 3.0L, no matter how you slice it.

 

[steelespike]

Re: Went to a 4blade

It appears that there are 2 3.0 models 130 hp and 150hp.
Your speeds sound like the 130 version.As Craze suggested your not likely to see 45mph.
My info puts both at 4600 wot rpm.So your 19 running 4500 is darn close you would ovewrrev with a 17" 3 blade.It is possible someone can suggest a more sofisticated prop ,Stiletto for instance.Unfortunately I can't suggest a pitch that would be ideal.Keep in mind that a couple of mph increase would likely the most you could expect.You might do a complete tuneup on the motor with a compression check.
How far is "up and down the lake" What is "all the time"
imo your motor isn't going to like that depending on the duration and frequency.

 

[craze1cars]

Re: Went to a 4blade

I think those HP #'s are even a stretch...

I once owned a 1992 Mercruiser "3.0L" in a 18 ft Rinker hull that was rated at 115 hp (FYI I never got that boat past 38 mph GPS...and I assure you I tried. It was happiest being propped right at 4,500 or 4,600). And the flagship of the 3.0 offered in that particular year was the "3.0LX", rated at 135 hp.

I admit I am not as familiar wtih the 1990 3.0 models...but they can't be that much different in HP ratings from my 1992.

Many of the older 3.0's were rated at 140 hp, but I think they measured at the crank instead of at the prop shaft like they have been doing for the past few decades. I've never heard of a 3.0 putting out 150 hp in any format, unless substantailly performance modified...rare for a 3.0 but a few have pulled it off.

 

[lonemust]

Re: Went to a 4blade

Craze you are right in your thinking.. the 3.0l that were rated at 140hp were measured at the flywheel instead of the prop.. I have a 3.0l merc (140hp) from 1970 in a '70 starcraft V180(18') fiberglass hull. I run a 14.5x23 right now, It takes a few to get on plane and I top out at 39mph on the depht finder.. I dont have a gps to check the speed with.. not sure on rpms right now.. I think my tach is off also, so i installed another tach yesterday. But it was in the late 70's to mid 80's that they started rating the engines at the prop instead of the flywheel..

 

[steelespike]

Re: Went to a 4blade

It seems to me that that setuop, a 17' with a 19" pitch, should be closer to over reving.
Though I think being an OMC with 1.86 ratio maybe that holds the rpm down a little.

 

[craze1cars]

Re: Went to a 4blade

Doesn't surprise me at all that it's not over-revving. My 1992 had a 1.98 ratio, I ran a 17 pitch prop most of the time...4,500 to 4,600 every time. With a 19 it would run about 4,200.

Now what DOES surprise me is that lonemust is running a 23 pitch prop. I have NEVER known a 3.0L runabout to be able to push a 23 pitch prop...of course he mentions questionable tach and "takes a few" to get on plane...so I suspect this one can't push a 23 either, and is currently way overpropped...