Prop Pitch

Dump

Cadet
Joined
Dec 31, 2003
Messages
26
I have a 1991 Sea Ray 270 Sundancer equiped with twin 4.3, 262 CID engines rated at 175 each. The engines have been well maintained and run fine. The boat is slow getting "out of the hole" and also is difficult to plane at slower speeds. Would new props with different pitch help to solve this problem? Also, would four blade props make any difference in the boat's planeing ability. Finally, could different props affect the fuel economy of the boat?
 

crazy charlie

Vice Admiral
Joined
May 22, 2003
Messages
5,581
Re: Prop Pitch

I have the same trouble with my 280 Regal and I purchased 4 blade props for it.I cant wait until spring to try them out.I did not get much feedback here on 4 blade props but i found a guy that deals in them and he a ton of experience with them.He was able to get me the right size for what I need and his prices were fantastic.Reply if you want his email address.Charlie
 

Dump

Cadet
Joined
Dec 31, 2003
Messages
26
Re: Prop Pitch

Crazy Charlie: Thanks, I would like the name of the individual you purchased your four blade props from. <br /><br />Dump
 

Jdeagro

iboats.com Partner
Joined
Jul 30, 2003
Messages
1,682
Re: Prop Pitch

Dump;<br /><br />Do you have trim tabs on the boat? What engine RPMs are you running at MAX Speed?<br /><br />If you have Tabs and are using them to plane they may be under sized. You should have no problem getting on plane.
 

ThomWV

Senior Chief Petty Officer
Joined
Dec 19, 2003
Messages
701
Re: Prop Pitch

Wait a minute here. None of the information given so far could give anyone any reason to make a suggestion as to what you need to do.<br /><br />You have to start with the two basics, what is your maximum RPM and what size props are you using right now. Don't worry if it has 2 blades, or 3 blades, or 4 blades or 5 blades. Deal with that question once you get your pitch right and you haven't begun to do that.<br /><br />Right off hand just from what you've said I'll bet you aren't able to crank over 4,000 RPM out of those engines and maybe even a lot less. Oh, top speed is meaningless too at this point.<br /><br />Thom
 

Boatist

Rear Admiral
Joined
Apr 22, 2002
Messages
4,552
Re: Prop Pitch

Dump<br />Need more info to give you any help.<br />1: Has boat always been slow to plane or is this something New?<br />2: What is your WOT RPMs ?<br />3: To select a new prop must know what your have now? Pitch, Size, Blades, Style, Cupped.<br />4: Due you have a lot of water in the Bildge or have you add a lot of gear?<br /><br />In general if both engines are running good then must check the bottom for and make sure it is clean. Four blade props will usually give you a little better hole shot but you loose a little top end. Yes any prop change Will affect fuel mileage. <br /><br />For best hole shot you want your WOT RPMs to be near the top of your RPM range. This will mean faster starts, but you will burn more fuel and lower top speed.<br /><br />If your WOT RPMs are near the lower end of your rpm range, you will have slower hole shot and have a higher top speed and get better fuel mileage.<br /><br />Example: My WOT RPM range is 4200-4600. I have two statainless steel props. 21 Foot Runabout with 24 by 12 bennett trim tabs.<br />Prop 1 13 1/4 by 17 pitch by 3, WOT RPMs 4600, Quick to plane and top speed 35 MPH.<br />Prop 2 13 3/8 by 19 pitch by 3, WOT RPMS 4200, Slower to plane but top speed 38 mph.<br /><br />I use Prop 1 in lakes and rivers where do a lot of starting and stopping for other boats or marineas and fuel mileage does not matter that much as usually short runs.<br /><br />I use Prop 2 In the ocean and San Francisco Bay area where make much longer runs and fuel mileage is more important. In ocean rare that we run over 20 to 25 MPH.<br /><br />Going to my favorite fishing spot Cordel Banks 26 miles offshore I will travel about 70 miles in a day. This is from both trip log in GPS and trip log Fish finder with a speed sensor. Some of this mileage is while drifting While fishing and I can not tell you the actual distance under power. Been there a lot of times and always around 70 Miles. <br />When I refill the boat after this trip with the 19 pitch it takes about 15 gallons to refill so about 4.6 Miles per Gallon. With the 17 Pitch it takes about 18 gallons to refill or 3.8 Miles per gallon. <br /><br />I ask several factory rep about 4 blade props for my boat and each told me really designed for the bass boat market and did not recommend for my boat. Remember the guy selling the prop is worst person to ask.<br /><br />Hope this helps
 
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