Prop Doctor Rx...?

[Girlfriend III]

Hey guys, need a suggestion. I have a 42 SeaRay Aft Cabin with 3116 Cat 350 in it. I am looking for faster cruising speed. Currently I cruise at 2000 rpm's @ 18.5 mph. I currently have nybril 4 blade props @20 x 23. In my quest for more speed( 4-6 mph), I am looking into new props. Lens prop shop states I should be running nybril 3 blade 20 x 21 for a cost of $1175 each plus $50 to cup each one. Does the spec's sound right for what I am looking to accomplish? I went to SeaRay's site and they stop at 32 foot boats for their prop calculator.

Any advise would be welcome.

Thank You!

 

[Dkruid 410]

I have a 2003 410 Sundancer with 3126 TA Cats and That is the same thing I was looking for. There is a thread one here with the discussion on what should be done with the props. I have 22X23 Nibral 4 blade and had them removed because I was not getting 2800 RPM at WOT. I have just gotten them back from the prop shop that Sea Ray sends them to and they had them sdjusted to 21.75X 21.75. I will let you know if that helped. The cost for the change from the prop shop was 975.00 for both props.

 

[osd9]

GF...What is your current WOT, fully loaded, with your current props? You should be able to reach 2800 + 50 or so. That's where you have to start.....your cruise speed will be what it is at ~2400 RPM after you have accomplished your specified WOT RPMs.

According to the parts manual for you boat....

http://www.searay.com/Archives_Manuals/Sea_Ray_Archives/parts_manuals/1996/1996_420_AFT_CABIN.pdf

.....on page 15, you should be running with 23 X 25 4 blade nibrals....That's a large difference from you have on there now.....

 

[Dancin Dave]

Dude you got the wrong props, Dom is correct 2400 rpms is cruise. Can you achieve 2800 rpms or even close?

 

[Asureyez]

WOW! That is a huge difference in props from spec to what you have. If you are already well below design load in prop size, then going lower isn't the issue to get to revs under load. One would suspect mechanical issues. Time for our resident Expert on these Cats ....

Frank?

 

[Girlfriend III]

Thanks Guys,
I really do appreciate your reply's. Dave, no I can't get over 2400...it is either the prop issue or the engines are goverened down?

Either way, looks like more money is involved. OSD9 would the props you suggested 23x 25 4 blade help me get there? And thanks for the link !

Thanks Again !

 

[fc3]

Page 37 shows spare props for 340 HP Cat diesels. It shows 21 x 24 4BC and 22 x 22 4B 71C props. You need to talk to someone who knows this boat. You can also try Sea Ray.

Best regards,
Frank

 

[osd9]

A few questions.

How confident are you with your tachs?

Your motors should be able to reach approximately 3100 in neutral at the dock...the max bare idle RPM. Can they each get there?

How clean is the bottom of your boat?

Going with a bigge diameter with more pitch would only make things worse.....

 

[Dancin Dave]

Call Searay, get the right props on the boat, run the boat with a cat mechanic with the tach gun, tweak the props if needed. Thats what I would do.

 

[osd9]

What Dave said...:thumbsup:

I would classify your current situation as "serious"....it needs to be addressed and fixed ASAP....you are overloading those motors.

 

[Girlfriend III]

Thanks again guys, I think I will take Dave's suggestions. Dom, the bottom of the boat is clean, just painted it last week, will have to wait to splash it to check rpm's at slip.