3blade prop vs./= 4blade prop

[BrentW]

hello, ive got a question for anyone who has some experience with props or just wants to chime in for that matter. I do not have any solid numbers to go by right now but that s not relly the base of my question. what im wondering is my boat sea ray 230 cuddy with mercruiser 5.7 260hp has a stock aluminum 3 blade, its 14.5x17p im thinking of buying a a new prop and was thinking of a 4 blade. now the boat seems to run fine now with the prop i have so if i was going to a 4 blade should i go with the same size as the 3 blade i have. or does it need to be a different pitch. once i put boat back in the water in about 2 weeks im going to get some solid test numbers back with my 3 blade prop and ill post them so maybe itll help determine which size to get, and if i can squeeze some more performance out of the boat id like to ofcourse. if i remember correctly and im 95% sure. last year i would hit wot specs with more trottle to go.my wot should be 4600 and id hit 4900 in calm river water with probably about 1/8th more trottle to go. but i know i need to get some solid and accurate numbers before any one can really help me , so thats what ill do soon. but for now if any one has advice on the 3 blade on 4 blade comparison let me know,thanks

 

[local825]

Re: 3blade prop vs./= 4blade prop

Hey i also have a sea-ray mines is only a Alpha 1 120hp, I dont no if you have the manual for that engine but as i read mines I found out it's the Pitch of the blades that play a major role on determining what type of speed/power you will get , My biggest problem is *&%####,field mice keep geting in to my prop and clogging up the water flow.......

 

[PROPer]

Re: 3blade prop vs./= 4blade prop

If you are truely getting around 4900 RPM with the current prop, then I would recomend sticking with a 17 pitch when moving to a 4-blade. This should move your RPMs down to the reccomended range.
What type of performace are you looking for? You will most likely get better top end with the 3-blade. The 4-blade should generally give you a better hole-shot and more cruising efficiency. But, this is all generally speaking until we know some hard data.

 

[90stingray]

Re: 3blade prop vs./= 4blade prop

Stick with the same pitch and same diameter and you will be happy. Buy a stainless if you can spare the cash. I went from a 3 to 4 blade. Night and day difference on holeshot. No big affect on top end.

 

[Brewman61]

Re: 3blade prop vs./= 4blade prop

See if your prop seller allows adjustment trades. Often, on a stainless steel prop, they'll let you go up or down in pitch if the prop you buy isn't quite right. There are certain restrictions, like returning the prop in good condition, etc...... And I've only seen it for SS props.
I went from a 21P 3 blade AL prop to a 4 blade SS 19P on my 18' fiberglass bowrider w/220 hp I/O. I get on plane easier, and stay up there at a lower speed. Had I needed to, I could have swapped the 19P for another equal prop had their suggestion been inadequate.

 

[BrentW]

Re: 3blade prop vs./= 4blade prop

hey thanks for all the suggestions and input so far, and i will get some true numbers and hard data on my real specs here soon.... thanks again, brent