Prostreeter

My question may not get alot of answers since most people here are at sea level but I sure need some help.I recently bought a 1997 Scarab 23 scs,502mpi,415 prop shaft hp and Bravo xr drive.We'll be boating at 5500 feet above sea level.The boat came with two props,a Mirage Plus 25 pitch and a Bravo 1 four blade 24p.

Our only prop shop here in Denver said the 25p will definitly not work at this elevation.The 24p prop is damaged but repairable and the prop shop thought that would be a good prop to use.My question guys is what would be a good base line prop to use.I would rather not put any money in either one of my props if I'm not going to use them.I really dont trust the opinion of our prop shop and it's still too cold to take the boat out for it's first test run.

throttleup

You can assume a power loss of about 1.5 - 2% per 1000 feet.

If you were at Chatfield Reservoir your elevation is about 5500 feet. That is a power loss of about 7.5 - 10%. If would be safe to go down in pitch the same amount.

If you were to assume the 25 Mirage plus ran at the proper RPM you would want something closer to a 23 Mirage Plus.

If you go to Grand Lake you would want something even smaller, maybe even a 21 Mirage.

The Bravo 24 is going to run about the same RPM as the 23 Mirage.

Prostreeter

Throttleup you must be from Denver or have been here.I live right on Chatfield and that's where we'll be doing 90% of our boating.The boat came from Michigan and was running the 25p prop,5k rpm's and gps'd at 74.3mph.

Our prop shop did suggest a Mirage plus 23p but I really didn't think he knew what he was talking about.Sounds like he might be right.So if I understand you I should try out the 23p and not have my 24p four blade cleaned up to use.Is that correct?

Thank you for your help.Greatly appreciated.

throttleup

You may want to baseline the 24 before you have any work done to it if the damage isn't too bad.

Either of the props could be worked to get the RPM up, you may want to baseline both of them and then decide what to do. But, your boating season is relatively short so it may be nice to have a prop ready at a moments notice.

It was pretty nice yesterday, the ice should be melting away and the boat ramp empty. The water will be cold! but it really never gets real warm anyway.

I was a deputy sheriff for 11 years in Jeffco, pretty familiar with Jefferson County.

Matt

ComfortablyNumb

Prostreeter,

I live in Castle Rock and go to Chatfield often. I think the ice should be off in a couple of weeks with the temperatures we are having.

I noticed in your tag line you mentioned that you are in the process of adding a procharger? If thats the case thats going to affect your choice of props.

Pat

Prostreeter

Matt,

Suprised the hell out of me when someone mentioned "Chatfield" on this forum.99% of the people on this forum would laugh if they saw what we get to boat on in Colorado.

The 4 blade is a little too banged up for a first test run.Jim's prop shop in Wheat Ridge is only charging me 135.00 to fix it up.He advised if this prop is not what I'm looking for it will have a much better trade in value.

Chatfield is open April 1st and that's why I'm getting all this prop stuff done now.Thanks again.

Prostreeter

Hello Pat,

Yes,the plan is to add a procharger sometime this summer.I would like to take the boat out for a while and get used to it on just the motor alone.Need to see how this boat behaves,runs and handles before adding another 100hp or so.

bbladesprops

Hey guys,

I had to kick in a couple comments. Since we all have a little in common here too. I lived in Boulder for 5 years in the early 80's. I attended Colorado Areo Tech at Jeffco Airport and obtained a Federal license to wrench on any and all aircraft. I know Jefferson Co. and Chatfield well too (Cherry Creek and the others too). Wow what a small world.

Matt, I knew you guys were from CO and moved to FL in the 1999ish time frame but didn't know you were from that specific area. Cool.

Anyway, one easy way to remember this stuff is..........go down 2" of pitch for every 5000 ft up in elevation you go up. This is a good basic rule of thumb. It can very but will get you started.

ComfortablyNumb

Prostreeter,

Have you visited the Prop Doctors on West Alameda? I seemed to recall that he has a 24' Baja with a big block. There may be some good advice there and he does repairs/trades/new and used etc. He was good to deal with.

Pat

Prostreeter

Thanks for the advise of the Prop Doctor Pat.Never heard of him.Will check it out though.

Steve