Prop help - 87 Sundancer 300

J

JVM225

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I've got an 87 30' Sundancer with twin 5.7 (350 ci) 260 HP Mercruiser IO's with Alpha 1(original equip) drives.
The boat is still covered and the drives are stored away at the boat yard.
I'm looking for a little advice if possible.
What are the correct size props and pitch for this boat?
I found a Sea Ray prop guide that suggests 14X19 as original equipment. Any thoughts on that?
Here is a really stupid question: Do they both turn the same way? I know they did a changeover in counter rotation around that time.
I'm not worried about pulling skiers with the boat or anything like that. I am more interested in a balance between decent cruising speed and fuel efficiency.
Can anyone help me?
Thanks in advance.
 
I have the same equipment in a 1989 model year Sundancer. Here is my experience with my particular boat. I bought the boat 3 years ago. It had the 14 x 19" aluminum props (both are CW rotation). The RPM that I could obtain at WOT was only in the 4000-4100 RPM range. After a tune up, wires, and carb and timing adjustment over a couple year period, performance improved a little but did not reach the specified WOT RPM rating that I was trying to obtain. The last solution was to change props which is what I've done. I settled on 14 1/2 x 17" aluminum props. With these props I am getting about 4500 RPM at WOT. It isn't perfect but acceptable. These props seem to work well over my normal operation range which is up to about 3500 RPM. My cruise RPM is 2800 to 3100 RPM. Fuel usage is in the area of 18 gph, give or take a little depending on the RPM. Your results will probably vary as our engines are probably at a different state of wear.
 
Thanks Play Dough. That info helps alot.
Is yours a 30' too? Sounds like we have almost the same boat.
Both are CW rotation? I was under the impression that all I/O's or Sterndrive engines were standard LH rotation and that the counter rotation for one was in the out drives. I thought that both props would have to spin inboard to move the boat forward and that if both spun the same way the boat would want to move sideways.
Thanks again.
 
Yes, I have a 30'. Both drives require a RH prop. I think there is probably some minimal amount of "prop walk" created by the duplicated rotation but it isn't noticeable to me although I've never piloted a boat with counter rotating props. It certainly doesn't create any problem. A propeller works like a screw being driven into water and because it's on a shaft it will propel the boat forward (or back if the rotation is reversed). The principle is the same as a screw into wood or an auger into the earth. The second number of the prop spec, ie. 17" is the pitch and theoretically is the distance the prop will travel in one revolution assuming no loss of motion due to slip, drag, etc.
 
Wasn't this posted as another question a few days ago?......Is this a Boat that you just bought and haven't been out on the water with yet?
 
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