Mercury 60hp CT prop question

[Hantsman]

Hey all,

New to the fourm, I'm hoping you guys can give me some insight/recommendations! I have a crestliner vision 1600 duel console with a Mercury 60 hp ct that doesn't seem to be hitting the recommended RPM range at WOT. Me, the wife and 2 small kids and some gear were in the boat about 500 lbs give or take. At WOT the tach was reading around 5200 rpm and reached a speed of 26 mph. No issues getting on plane and pulled a tube no problem. Does this seem reasonable or is there some tweaking I can do? Currently has a 4 blade merc spitfire 13.8 x 13 prop.

 

[ThomW]

What is the recommended WOT for your motor?

 

[Hantsman]

5500 to 6000 rpm.. would going to a 3 blade help?

 

[ThomW]

In general, switching from the 4 to 3 blade with the same pitch would give you some additional RPM's. It takes more HP to turn a 4 blade prop, so you typically get less RPM's out of a 4 blade. You may lose some hole shot performance, but I think a 3 blade of the same pitch would give you a couple hundred more RPM's and a few more MPH on the top end.

 

[Hantsman]

Ok. I think I'll order a turning point 3 blade prop, they seem reasonably priced. Thanks

 

[JimS123]

Ok. I think I'll order a turning point 3 blade prop, they seem reasonably priced. Thanks

Before you do anything, verify your rpm and speed data. I also have a 60CT and when I installed a VesselView I found that the tach on the dashboard was wrong.

If your performance (plane, ) is not an issue, your prop probably isn't too far off.

 

[Hantsman]

Ok. How far off was your rpm? What kind of speeds are u getting?

 

[Silvertip]

It is common to suspect a given prop is the cause of poor performance so money is spent needlessly when the problem may be a good tune up is in order because the engine is simply not making full power. Things like the throttle being misadjusted so it's not opening fully. Check the cheap stuff first, then start playing with props if it turns out the engine is indeed performing properly.

 

[JimS123]

Ok. How far off was your rpm? What kind of speeds are u getting?

Ours is a 15' Whaler that weighs about 2000 # loaded. I'm turning a 14" SS 3-blade Vengeance. WOT is 5950 rpm at ~35 mph in a very light chop. These are verified numbers with GPS and VesselView.

The tach was reading about 600 rpm high. When it was installed the setting switch was wrong. Once I adjusted it to the proper pulse rate its now spot on.

I'm not saying yours is wrong. My other boat came from the factory perfect. I'm just saying that everything needs to be checked. Bad data is worse than no data.

 

[Hantsman]

I'd be super happy if I could get 35 mph. Next time I'll use the GPS. I don't have much faith in the boat speedo. The motor is 2 years old and everything seems to be working fine. Checked the plugs and compression all looked good. Throttle linkage seems to be adjusted properly too.

 

[Texasmark]

Ok. I think I'll order a turning point 3 blade prop, they seem reasonably priced. Thanks

If you go with the TP Hustler, you may get a ported prop. I have 4 or 5 of their props in 13+ diameters and they are all ported (holes under the leading edges of the blades. This improves the hole shot but you said yours was fine already.

The question is, how? You have to be going fast enough for new water to seal off the ports such that they essentially disappear in the prop thrust equation. Otherwise you will be "leaking" exhaust gasses at WOT which will raise the RPMs but cause more prop slip and lower your MPH for what it would be without ports.

If you do as you said and the ports become a problem, just get some JB weld and seal them off.

 

[Hantsman]

Ok so I tried a 3 blade 13 pitch hustler prop got about the same speed but rpms went from 5200 to over 6200! Maybe a 3 blade 15 pitch would hit the sweet spot?

 

[QBhoy]

Agree with an above comment. If you are trying to fine tune, get a VesselView mobile to see the exact rpms. Gauges aren’t accurate.
Are you trimming up ? Your speed isn’t too bad at all.

 

[Hantsman]

Figured I'd give an update! I tried the hustler 3 blade 15 pitch prop and the wot rpms dropped to 5200. Looks like the hustler 3 blade 13 pitch is what I will be sticking with. I didn't expect my max rpms to drop that much!

 

[airshot]

Even though the pitch is the same, different props from different mfgrs can give different results !! Sometimes it pays to pay the bigfer bucks and let a prop specialist from a prop shop sort it out. They will normally let you try different props and exchange them as long as they arent damaged. Now you can try all the different props to get the best results.....by the way, my 16' aluminum side console with 40 hp Merc weighs over 1000 lbs with 4 batteries on board and she will do 31 mph by gps....never trust a pressure speedo, a gps is a must !!