Prop Selection - Prop Wizard Calc

[Eddie P]

Hi all, I just bought a 1999 Stingray 220DS. Mercruiser 5.7L, 250hp, carburted, Alpha 1. I boat at Tahoe and surrounding lakes - 5500 to 6200 feet elevation. Ive taken the boat out locally, great fun and really good running rig so far aside from a prop that needs a bit of cleanup. A few dents in the leading edges, rough in places and wear on the surface, so I'm looking for a prop that will do well at Tahoe - maybe less pitch. I'll have the current prop overhauled and keep it as a spare just in case option. The boat yard who did a pre-buy inspection told me about the prop but said it was OK to run like that but better to get it overhauled. I want to get it rectified asap.

I have small kids and cruise around mostly. Top range speeds, hole shot, etc are good but take second consideration to decent cruising performance, etc.

For the life of me I can't find out what the current prop pitch is - not stamped anywhere I can see it. It measures 15.0 inches, it's a 3 blader. I might have lost a couple hundred RPM from sea level, the boats old home, to the mountain lakes but to be honest I ran it very, very brifly at just below full throttle to see if it came close. I did not want to run it hard at all, if it's over propped for the higher altitudes - mostly just crusied around. Seemed like 4500 to 4700 RPM max at sea level, maybe 4100 plus up here at mountain elevations... but I could be wrong I didn't want to really abuse the engine by pushing revs too much with a non optimized prop at high elevation and a sea level setup.

I was cruising the internet for a little info and came across this page;
http://dansdiscountprops.com/BuyNow...=1&boatAltitude=6000&waterSports=1&cruising=1

It has a prop calculator on it and it came up with a 3 bladed 15.25 by 15 prop, aluminium.

What do you guys think.

 

[Eddie P]

Re: Prop Selection - Prop Wizard Calc

Come on guys, a little help, any ideas are good to hear

 

[rndn]

Re: Prop Selection - Prop Wizard Calc

I would guess 15 or 17 inch pitch would be a good starting point, however without knowing what the current prop is, it will be a guess.

 

[tysonnathan]

Re: Prop Selection - Prop Wizard Calc

I have always used a 19p prop on my bowriders. I have had one on my 18' for a long time and currently am running the same on my 20' bowrider. Has served as a good all around prop for cruising, skiing, etc. Again, without knowing what you have its hard to make a recommendation...

 

[rndn]

Re: Prop Selection - Prop Wizard Calc

With a 22 foot boat I would "guess" a 19 would be too much pitch.

 

[Eddie P]

Re: Prop Selection - Prop Wizard Calc

Thanks for the helpful replies Gents.

I took the prop off last week and saw that it was a 15 inch (as measured) by 17, stamped inside the hub area. So I went into the local prop shop and talked a bit about it with the shop owner.

He was saying that for my engine, a Mercruiser 5.7L 250HP motor and an Alpha 1 outdrive with standard gear ratios, a 15x15 to a 15x19 would be about normal. For sea level, some would have 15x19, some would go with 15x17 for an all around prop. For mountain lakes at 5-6K in elevation, a 15x15 might be the ticket. Since I will boat mostly at Tahoe and surrounding lakes, I'll be anywhere from 5000 to 6200 feet in elevation.

Since I have a 15x17 prop, and I needed the prop to be overhauled due to surface and leading edge condition, he also offered to bring down the pitch of the prop by two inches (for high mountain lake ops) based on the performance I was getting at sea level and then at 5500 feet.

So in a few days I'll be picking up my overhauled prop from the shop to put it back on, and then get some experience with it. I'll report back on what the results are so that anyone using the search function in the future can get a little bit out of what was making a new boat owner like me ponder for a bit.

If anyone has any food for thought please feel free to chime in. Again, thanks to you all for the comments and ideas.

 

[tysonnathan]

Re: Prop Selection - Prop Wizard Calc

let us know how it works out...

 

[Eddie P]

Fantastic Results

Fantastic Results

I tried to post here a few weeks ago but it seems either the forum has been down for weeks or I just have not had access to it.

The re-conditioned prop has been a good thing.

Original prop was a 15x17 three bladed aluminium one. It was pitted and the leading edges were slightly deformed from small foreign object damage and such.

I wanted the prop overhauled and also re-pitched becasue as the new boat owner I am operating out of Lake Tahoe at 6200 feet elevation vesus the previous sea level lake home port of the boat.

The prop overhaul shop refurbished the prop and re pitched it to a 15x15. It cost me 85 bucks and it was well worth it. The finished product looks almost new and works great.

My running RPM is now 4500 with 8 people on board and a few hundred pounds under the max load. Normal RPM range in the maintenance manual calls for max RPM to be 4500-4700. Pretty realistic, and good performance up to planing speed with a heavy load inside the boat and the engine/outdrive/prop purrs. I'm running mostly at 3000 RPM for cruising speed and only brought the power up to max blast a couple times to validate the performance. It just does not need to be worked hard, nor do I want to add the wear and tear to the engine and outdrive. I think that says a lot for the prop, the engine and the hull design - they are all playing nicely together.

I know I can get even better results by having the carburetor fine tuned for altitude, and I will probably have that done this week by a marine shop. I could also play with a SS prop of different configuration but I'll take that time and spend that money somewhere else this season.

Thanks to all for posting their successes and suggestions here, you have all helped me out greatly.

Happy boating

 

[choo choo man]

Re: Fantastic Results

Re: Fantastic Results

You may at some point decide to get a second prop for different altitudes/applications. Also, it never hurts to keep a second prop and wrench on board in case of a mishap.