Trying to find the right prop

[leftcoast]

I have 2006 185 Double Eagle with a 150hp Etec. I'm having a hard time understand this prop thing. The motor came with a 21 pitch 3 blade stainless. I topped out with no load at 5200 so I switched to a 19 pitch 4 blade it got less around 5000.
Now I'm onto a 19 pitch 3 blade and on the ocean I could only get 4800. This prop is the best at cruise 3500 and getting 30 knots really happy with that but am worried about not getting high enough rpm and doing damage to the motor. This doesn't seem to make sense to me how could I go down a pitch and lose RPM.
Maybe I need to double check my numbers but I'm sure that's what I was reading. Maybe I should just go back to the 21 pitch and call it done.

Am I missing something. What do you prop experts think is the prop for me.

Thanks guys.

 

[Rayvon]

Your not missing something unless your numbers are wrong .Going down in pitch should increase your RPM.I would check the 19 pitch 3 blade to see if it's been altered (repitched). That boat w/a 150 should be in the 19-21 range I would think.My son has the same boat w/a 150 Yam 4 stroke that fly's.I'll check with him to see what prop he's running.

 

[leftcoast]

Your not missing something unless your numbers are wrong .Going down in pitch should increase your RPM.I would check the 19 pitch 3 blade to see if it's been altered (repitched). That boat w/a 150 should be in the 19-21 range I would think.My son has the same boat w/a 150 Yam 4 stroke that fly's.I'll check with him to see what prop he's running.

Does running on fresh water vs salt water effect your RPM at all? Let me know what your son says for his prop.

The only difference was when I tried the 21 pitch I was along and half a tank of fuel when I tried the 19 I was with another guy full tank and gear.

 

[salmonkiller01]

The weight makes a difference, are they the same diameter 21,19
?

 

[leftcoast]

The weight makes a difference, are they the same diameter 21,19
?

19 is 14 1/2 and 21 is 14 1/4. I guess I should try the 21 with a load I'm worried it might be hard to get our of the hole with a big load. Just confused why the 19 isn't the ticket since I'm told most of these boats work great with a 19.

 

[salmonkiller01]

Try a 19 in 14 1/4 diameter, with props dropping the pitch usually gets higher rpm, but increasing diameter negates the pitch drop.

 

[halimark]

I have same boat make, model, year with welded aluminum hardtop so probably a little heavier. Motor is 140 4 stroke and my prop is a 13x19 solas stainless, 3 blade. Came with motor, never had a problem, loaded, unloaded seams all the same. Not sure WO but cruise at 4000rpm and 30 knts all day. I have had no issues with setup.

HM

 

[JAC]

Change to a 17p and you should be good to go

 

[leftcoast]

Change to a 17p and you should be good to go

That was the next plan. Thanks guys for taking the time to give me some input

 

[Canso]

You have too much diameter, 14.5" diameter is good for big heavy stern drive boat. 13" diameter is for lighter outboard applications.
I would be trying 13.5x19 or 13x19 for your type of boat.

 

[trophywife]

yup . prop is too big, go with what canso said.

 

[CIVANO]

http://www.formulapropeller.com/propellers.html

maybe some helpful information

 

[JAC]

I have found 17p to work really well with smaller boats you want to get right up to make rpm. Don't want to drive around in 5th gear all the time

 

[ericl]

What prop should you be using? The original one.

As mentioned, diameter matters. 4 blades are slower than 3 blades (more drag) but smoother & more fuel efficient at less than full speed. Some props have a cup which is the same as adding pitch. The cup allows you to mount the motor higher (less drag).

 

[JAC]

If you find your boat is stern heavy a 4 blade is nice because it helps lift your stern. Better control at slow speeds and reverse with a 4 blade