Propping Down for Elevation?

I have a question regarding propping down... I will be heading to Tahoe at the end of September and I'll be dragging the tritoon up. Should I downsize in pitch or diameter? Or both? I wont have any test and tune time so its a shot in the dark. I know when I boat Big Bear there is a noticeable power loss.
According to the elevation and density HP calculators along with the weather history for the time of year I can expect a 39-44ph loss which is not too much more than what the calculators say I lose on Big Bear.

Everything I am reading it seems a pitch change is the way to go as opposed to diameter. What about the number of blades?

Any tips would be appreciated.

Constant840 said:

I have a question regarding propping down... I will be heading to Tahoe at the end of September and I'll be dragging the tritoon up. Should I downsize in pitch or diameter? Or both? I wont have any test and tune time so its a shot in the dark. I know when I boat Big Bear there is a noticeable power loss.
According to the elevation and density HP calculators along with the weather history for the time of year I can expect a 39-44ph loss which is not too much more than what the calculators say I lose on Big Bear.

Everything I am reading it seems a pitch change is the way to go as opposed to diameter. What about the number of blades?

Any tips would be appreciated.

Click to expand...

Keep the same Diameter and number of blades and go down 2 inches in pitch for every 3000 ft up in elevation and you should be fine.

Constant840 said:

I have a question regarding propping down... I will be heading to Tahoe at the end of September and I'll be dragging the tritoon up.

Everything I am reading it seems a pitch change is the way to go as opposed to diameter. What about the number of blades?

Any tips would be appreciated.

Click to expand...

Tahoe has a surface elevation of 6225 ft plus the density altitude factors, for a hot summer day the motor thinks its at 8-9000 ft

We drop 4-6" of pitch going to Tahoe,

Tahoe is a big bowl and it gets rough in afternoon, propping down gives less speed but more throttle response in rougher water

What prop and motor package are you using ?

My go to right now is a stainless 14.5x15" on a 175 Evinrude Etec. It normally turns right at 5400, which from what I have read is where the engine wants to be. It recently has lost 300rpm, but I'm not sure that isn't attributed to a heavier than usual weight?

So loosing 2" for every 3000', I should think about a 14.5x11"?

Constant840 said:

My go to right now is a stainless 14.5x15" on a 175 Evinrude Etec. It normally turns right at 5400, which from what I have read is where the engine wants to be. It recently has lost 300rpm, but I'm not sure that isn't attributed to a heavier than usual weight?

So loosing 2" for every 3000', I should think about a 14.5x11"?

Click to expand...

Big Bear is @ 6750 surface elevation !
Your performance should be close @ Tahoe

Outboards can lose a few rpm in the summer months, next time your in for service have them do a cylinder leak down test, but first try a spray can of mercury decarbonizer down the intake to clean the piston and rings

Tahoe, is a pain in the ASS these days to boat on !

We used to roll in just before sunrise at the public ramps to get a couple cheap parking spots
and run a big circle around the lake while its smooth, our GPS was nice it showed many of the rock hazards near the shore line on the chart

I hadn't realized Big Bear was 500ft higher. For some reason google earth gave me a 7000+ elevation for Tahoe?
I'll get some decabonizer and see if it helps.
Now to find a 4 blade 14.5x11 prop.... I found a 3 blade 14x11, nothing with 4.

Why is Tahoe a pain in the ass? Are the many hidden obstructions? I have been reading about the water level causing some trouble for people and props but not much else. Seems the seasonal mussel inspection stations pack up a day or two after we arrive so getting that done will be a priority as I'd rather not drive all around town to get it done.
I have visited many times and swore the next time I would boat it. Not too thrilled to tow all the way up there, but I want to run my own boat as opposed to renting a bayliner or something of the like. We are staying in Tahoe City. I am hoping to get a day down the west side and a day down the east side.

BigSteve said:

Big Bear is @ 6750 surface elevation !
Your performance should be close @ Tahoe

Outboards can lose a few rpm in the summer months, next time your in for service have them do a cylinder leak down test, but first try a spray can of mercury decarbonizer down the intake to clean the piston and rings

Tahoe, is a pain in the ASS these days to boat on !

We used to roll in just before sunrise at the public ramps to get a couple cheap parking spots
and run a big circle around the lake while its smooth, our GPS was nice it showed many of the rock hazards near the shore line on the chart

Click to expand...

Steve, I am heading to Big Bear this weekend and bringing the boat. Last time I was up there, about 5 years ago, I was running my 22' Cole with 175 Black Max and 21 pitch 3 blade. Could barely get the boat to plane. The Eliminator is a heavier boat, but the 225 ProMax is a bigger motor. I only have 2 props right now, the 22p Five Blade and 23p 3 blade. Can I use either one of those? If not, what pitch should I go down to?? I have access to smaller pitch props to test out for the weekend if need be.

OldSchoolBoats said:

Steve, I am heading to Big Bear this weekend and bringing the boat. Last time I was up there, about 5 years ago, I was running my 22' Cole with 175 Black Max and 21 pitch 3 blade. Could barely get the boat to plane. The Eliminator is a heavier boat, but the 225 ProMax is a bigger motor. I only have 2 props right now, the 22p Five Blade and 23p 3 blade. Can I use either one of those? If not, what pitch should I go down to?? I have access to smaller pitch props to test out for the weekend if need be.

Click to expand...

How did the boat run a Big Bear? Did you make any prop changes?

I ordered a 16x13 and a 15.5x11 both in aluminum. We'll see how they run on Tahoe at the end of the month.

Boat ran great. My mechanic let me borrow a ventilated 3 blade, 21 pitch but I didnt use it. Just ran my 5 blade and it did fine. Boat planed quick just like at the river. I did some running around on it early in the morning and I did notice a little top end lost. Other than that, it did fine.