Prop recommendations for Mercruiser 165 at 5k elevation?

[ianboat]

Hi,
We're very impressed with everyone's knowledge on this site.
So, we're hoping you can help us.

We usually pull our son (& friends) on wakeboards, but now he's started using a single ski, and we NEED MORE POWER (also, he has gotten much bigger - as kids do!).

One big reason that we need help is that we run it in lakes at 4,000' to 6,000' elevation (including Lake Tahoe).

Here are the basics on the boat:
Engine: 1972 Mercruiser 165 hp straight-line 6
Boat: 1972 SeaRay 19' (SRV 190) - 6 seats - closed bow

WOT should be about 4,300, but we have not checked it.

Current prop is stock - 14.5 x 17 aluminum

Any ideas on what might be a good prop for high elevation use for this boat?

 

[steelespike]

Re: Prop recommendations for Mercruiser 165 at 5k elevation?

The best prop is that which gets your motor to its rated rpm at speed.
A 1" decrease in pitch will add ABOUT 200 rpm.If you generally run at 4 to 5000 you might consider rejetting the carb for that elevation.Then select a prop based on your performance.imo a prop change in this case is like a bandaid when you need minor surgery.Of course I don't operate at those elevations and a prop change may be the way to go if your likely to be running at lower elevations too.

 

[hwsiii]

Re: Prop recommendations for Mercruiser 165 at 5k elevation?

Ian, load the boat with the normal load you carry on these trips and tell us the RPM at WOT and the speed, and we an help you.

H

 

[ianboat]

Re: Prop recommendations for Mercruiser 165 at 5k elevation?

Thanks everyone!
- we will check the WOT next weekend, and then hopefully it will allow into more specific feedback - such as 3 blade vs 4, change in pitch, etc.

 

[ianboat]

Re: Prop recommendations for Mercruiser 165 at 5k elevation?

WOT info for this boat:

We took the boat out yesterday - on a cool (temp 65), choppy day.

WOT was 3400 -- with about 800 lbs of passengers in the boat - 5,000' elevation.

WOT SHOULD BE 3900 - 4300

Current prop is: 14.5 x 17 aluminum
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Mercruiser recommendation for 17'-19' boat is 15 x 23 - 3 blade aluminum
Mercruiser recommendation for 19'-21' boat is 15 1/4 x 21 - 3 blade aluminum.

Our boat is 19', so we're kind of in the middle.

We need to adjust for elevation, but I'm not sure how that works...

Any recommendations would be appreciated!