New boat, need prop advice

[nuffsaid]

I just purchased a used Lowe 2008 FM165sc from Cabela's in Sidney, NE. The boat has a 50 hp Merc two stroke with a 15 pitch Merc aluminum 3 blade prop. I took the boat out last weekend, and it is very apparent the prop is way off. I went to a lake that is close to home, elevation 4800 ft and the rpms would max out at 4500 and the boat would only go 24 mph by my gps. I had a full tank of gas, an ice chest, fishing gear, 20 lb anchor and two adults on board, there are two batteries and the live well was empty. The next day, I went to another little lake to hit ice off and catch some trout, the elevation is 6200 ft and the motor would only pull to 4000 rpm's and the boat had a hard time getting on plane. So, the million dollar question, what prop pitch is going to work for me? I will be fishing lakes in Northern Wyoming, Montana and one or two trips to Canada per year. On my next Canada trip coming up in June, there will be 3 of us fishing out of this boat. I just ordered a 10 7/8x11 pitch Black Max prop based on the information available to me. Did I make a good decision? What top speed can I expect with this prop, how slow should I be able to troll? Thanks in advance

 

[nuffsaid]

Re: New boat, need prop advice

Does anyone have any experience with altitude vs. prop pitch, with a 50 hp size motor?

 

[marcortez]

Re: New boat, need prop advice

Does anyone have any experience with altitude vs. prop pitch, with a 50 hp size motor?

The higher the elevation above sea level, the less oxygen in the air.
Less oxygen getting into the "burn" mixture of your fuel, directly relates to the burn efficiency in the cylinders.
Therefore, there is less power produced.

This is why mountain climbers WAY up there use a breathing apparatus.

Your prop could care less how high you are......however the powerhead does.

Hopes the makes a little sense.....

Going from a 15" pitch to a 11" pitch seems a little drastic....but the deed has been done. Go check it out and see how it performs for you.
Maybe you can exchange it if the RPM's are not near, or dead-on with the WOT ratings.

 

[nuffsaid]

Re: New boat, need prop advice

I know that going from a 15 to an 11 seems like a big jump, but I need to change at least 1000 rpms and based on 200 rpms per inch of prop, I hope it works. I have seen where people with the exact same setup as mine weren't happy with a 13 pitch prop and went to a 12 and were happy, but they were close to see level, hence my decision for an 11. I also used an on line prop whiz calulator and with my information that I put into it, it came up with an 11 pitch as best all around. I am just wanting to ask people with more experience that me with boats. If it was a 4x4 or a diesel pickup, I would be the one you would ask.

 

[nuffsaid]

Re: New boat, need prop advice

I ordered an 11 pitch Merc quicksilver prop, but it didn't show up in time to take it fishing yesterday. I only had myself in the boat, once the engine was warmed up and running smooth, the boat would achieve 25.4 mph @ 4200 rpms. Does this low rpm seem like it will be corrected with the 11 pitch prop? The lake I was at was 6200 ft. I want the boat to pull heavy well because I am planning on taking the boat to canada in June and there will be three of us and gear fishing.

 

[steelespike]

Re: New boat, need prop advice

While the 11 may be a little light your motor will be much happier than being lugged
with a larger pitch.And will be more pleasant to use.If she revs to high back off a little.It will surely be more happy with a load and less likely to over rev at that altittude.

 

[nuffsaid]

Re: New boat, need prop advice

Thanks for the reply, I got the prop, now I just need a couple hours to take it out and see how she does. I don't plan on running wot a lot, I just want a good fast up on plane and comfortable cruising with a little extra left over and some reasonable fuel economy. I will post my results when I get it back out on the lake, hopefully saturday.

 

[nuffsaid]

Re: New boat, need prop advice

I got a chance to take my boat out today with my new 11 P prop and it worked great. Last time on the lake at 6200 ft, the most I could pull with just me in the boat was 4200 rpms and 25 mph, today with new prop, 5200 rpms and 27 mph with about a 20 mph wind.