Prop selection

[itguy]

2002 ProCraft 180 Combo with a 2001 Mercury 150 XR6. 14 1/4 x 24 SS Turbo prop. I ran these specs through Merc's site and they're calling for a 21p prop.

Recently purchased and only had out three times.

First time - Four adults, 59mph GPS..didn't record RPM's

Second time - Two adults, 50mph GPS, 4600 rpm

Today - Two adults, 23 gal fuel, 54mph GPS, 5000 rpm

After my second outing I thought something was wrong due to the decrease in performace. It acted "OK" but there was a loss of speed. After posting the problem, some people thought I fouled the plugs due to excessive idling. I just had the boat serviced, new impeller, plugs, compression test, etc... Everything checked out just fine.

I'm a little concerned I have yet to reach the results of my first outing with a full load. I guess if I never saw the speed I wouldn't be concerned but I still keep thinking something else is wrong even though it was just serviced.

I believe I should be running 5600 RPM's according to the manual. The motor sits 6 1/2" below pad which is the same as other Combo owners from what I've found out.

Any suggestions?

 

[steelespike]

Re: Prop selection

Is the 3rd run after a tuneup? Don't forget speed can be affected by wind,
wave action,current and weight distribution.Glass smooth water may not be as fast as light wave action.It does appear the motor can't quite twist the 23 up.I think I would try it with four again maybe it likes the weight placement better.

 

[itguy]

Re: Prop selection

Hey - This is my third run since I've owned the boat, first run after tune-up. The water was like glass this morning but I thought that would be the best situation. The first time we had some wind and the water was a little rough.

I pulled the plugs a few minutes ago and half of the white porcelain part (can't remember name) appeared to be burned color. This is how the old plugs looked so I guess it's normal. This is my first boat so I'm still learning!

 

[Dhadley]

Re: Prop selection

The boat will be somewhat faster on a slight chop compared to glass smooth water. What about fuel? Are you using the same 87 octane? Ethanol or non-ethanol?

When you say the motor is 6 1/2" below the pad we'll assume you're talking about the propshaft. That may be a bit low for a Turbo.