Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: prop question for 40hp Merc 4 Stroke
Posted by waco72 on 08/18/10 - 7:36 PM
#1
Sorry if this has been discussed many times before but I am looking for some advice. I have a 2008 130 Sport with a 40hp Merc EFI Four Stroke. I have tried adjusting the trim every which way, moving passengers (usually my 2 small kids and me) and still seems that no matter what I do, usually at WOT I can only get about 5000-5200 rpms. The manual says it should be running between 5500-6000. Does this sound right or does anyone think I could get more in terms of top end and or pulling the kids on a tube? It has the stock prop that came with the engine. Thanks
Posted by Joe Kriz on 08/18/10 - 7:42 PM
#2
What pitch prop do you have now?
When testing the WOT speed and RPM's, you should have a light or normal load.
Posted by waco72 on 08/20/10 - 7:12 AM
#3
It was the stock prop that came with the engine. I can't find where it says what the pitch is. I heard that it was stamped on it on the inside but I haven't removed the prop yet to look, thanks
Posted by DWinter on 08/20/10 - 3:44 PM
#4
It's usually on the the exterior of the hub where the prop nut is.
Posted by waco72 on 08/21/10 - 11:05 AM
#5
I found the sticker and it looks like its 13 x 26, 2:00 x 1, thanks for your help, I think I am looking for maybe quicker planing and top end if it's possible. It seems like even without a full load I am only getting up to about 5200 rpms.
Posted by Tom W Clark on 08/21/10 - 12:18 PM
#6
The sticker is on the gearcase and refers to the gear ratio (13 teeth x 26 teeth is a 2:1 ratio). It has nothing to do with the propeller pitch which is what we need to know to make a recommendation.
As Duane points out, the propeller size will be on the propeller itself. Look and see what it says. You may have to remove the propeller to see this.
Posted by waco72 on 08/21/10 - 1:08 PM
#7
ok thanks, new to boating as you can tell
Posted by Ric232 on 08/25/10 - 6:07 PM
#8
Your prop should be 14P. I have your exact same boat. Mine runs about 6150 at WOT (wide open throttle) with just me in the boat. I only weigh 140 lbs so this helps. Each additional person causes the RPM at WOT to drop significantly. Since you're new to boating, I'm wondering if you're not using enough trim at WOT to reach the recommended RPM range. It can be tough to do this sometimes in a 13 because the boat starts to porpoise (bow bounces up and down) even with a little trim. The key is to apply trim slowly as the boat accelerates. The faster the boat is going, the more trim it will tolerate before starting to porpoise. BTW, to find the pitch, look at the outside of the prop hub (between the blades). There is a long number stamped into the hub. It can be hard to read sometimes because it is painted over. I think the pitch (14P) appears at the end of the number.
Edited by Ric232 on 08/25/10 - 6:07 PM