Yet another prop change....heavy boat=big ears?

[WTP07]

So the lake laid down a bit today and I got a chance to take a cruise down to another harbour an hour or so away.

I got the top end up to 32 MPH at 4700 RPM. It keeps it on plane at 16 MPH around 3k RPM.

Overall, VERY happy with this new prop. :thumbsup:

 

[stevea661]

So the lake laid down a bit today and I got a chance to take a cruise down to another harbour an hour or so away.

I got the top end up to 32 MPH at 4700 RPM. It keeps it on plane at 16 MPH around 3k RPM.

Overall, VERY happy with this new prop. :thumbsup:

Just to be sure the prop is 16 diameter by 14 pitch and you have between 1/2 and 3/4 inch distance between the cav plate and the top of the blade? could you measure the distance from the top of the blade to the bottom of the cav plate and post what that number is, I am getting 30 mph at 3400 rpm wot 15.8 x 15 on the same boat with an omc drive and can't figure it out:huh:. Speed is ok but rpm is too low and I don't want to eat the motor or the drive. Thanks, Steve

 

[Tail Chaser 661]

So the lake laid down a bit today and I got a chance to take a cruise down to another harbour an hour or so away.

I got the top end up to 32 MPH at 4700 RPM. It keeps it on plane at 16 MPH around 3k RPM.

Overall, VERY happy with this new prop. :thumbsup:

glad your very happy with the prop. Being able to spin 4700rpm will help your drive last.

steve,
I'll check the prop measurement on Monday.
Forgot you have the OMC when I offered my 14"P prop.
The Alpha 1 GR are 1.50:1 and 1.47:1 That may help the Mercs spin the props a very small amount easier.
The B3 DA and Alpha 1 DA with the 5.7 seem to be spinning at least 3800rpm at 30 mph. I still think maybe your tach might be sticking with your low 30mph rpm numbers
I didn't like the fact that the 86 268DA had thicker stringers then mine. Mine are 6"H X 2.75"W now :lol: That should hold the extra 500 lbs of fuel and the bigger drivetrain.

 

[stevea661]

glad your very happy with the prop. Being able to spin 4700rpm will help your drive last.

steve,
I'll check the prop measurement on Monday.
Forgot you have the OMC when I offered my 14"P prop.
The Alpha 1 GR are 1.50:1 and 1.47:1 That may help the Mercs spin the props a very small amount easier.
The B3 DA and Alpha 1 DA with the 5.7 seem to be spinning at least 3800rpm at 30 mph. I still think maybe your tach might be sticking with your low 30mph rpm numbers
I didn't like the fact that the 86 268DA had thicker stringers then mine. Mine are 6"H X 2.75"W now :lol: That should hold the extra 500 lbs of fuel and the bigger drivetrain.

You stringers ar oh so big, oh so large , oh so all incompasing and now they are bigger than mine.:lol: thanks for checking on the measurment.

 

[silver0306]

Now i have no idea what size prop i had or have. i spun the hub on a smaller eared prop and had a large (elephant ear prop what someone told me ) i was at full speed at 4400 rpm at 27 mph now im at 33 mph at 4100 rpm and i can stay on plane at 3400 rpm. what a change in the ride.

 

[brains06]

So the lake laid down a bit today and I got a chance to take a cruise down to another harbour an hour or so away.

I got the top end up to 32 MPH at 4700 RPM. It keeps it on plane at 16 MPH around 3k RPM.

Overall, VERY happy with this new prop. :thumbsup:

Ok so we've heard 16 x 16; 15.25 x 15, and 16 x 14.

I have experience with the first two and like them both...but I'm intriged by the 16 x 14. I'm not running quite right at the moment so after a tune up I may pull some numbers with both 16 x 16 and 15.25. I think what we need to do or consider doing is making a base line test thread for each engine. Over the last month or so I can say I've posted at least 15 times on this very subject. This is not a complaint though. With prop pitch and RPM's being the single biggest performance change/mod we can make nearly on the fly its really good that people are smart enough to ask before doing something stupid. So I'm gonna see what I can find out and maybe start a thread based on my findings with the 350. It would be great to see a sticky on the subject with each of the more popular engines. Also we havent really dug into some of the variables that come with finding these numbers along with fuel burn (another ridiculously hot topic), such as tab usage, boat weight, direction of travel vs. current and so on. For example...

1978 260 Sundancer single 5.7 merc.
5100# dry
1/2 tank
tabs fully retracted or bow up
Traveling UPSTREAM/DOWNSTREAM with a 15.25 x 15 prop
3200 rpm - 17 mph/19
3600 rpm - 23.5/26
4000 rpm - 26/29
4400 rpm - 31/36

These numbers are also with my canvas down and just me. I've hit 36 though with my 300# buddy on board though. I'll have to check the numbers for the 16 x 16 but if I recall my midrange numbers were better but top end wasnt as good.....I probably need to switch it huh? I'll have to test it out and see. Either way, I'll get this thread started and lets see what we find.