New Prop for Mercruiser 260

[MelLandry]

There are a billion props out there... and I don't know where to start.

I have a Mercruiser 260. It is currently underproped with a 19 pitch, SS three blade.

I wish I could provide more info on the prop and WOT, but I don't have it with me at the moment. If I recall correctly, I can trun about 5400 RPM and it'll run about 46mph. I understand my WOT SHOULD be between 4400/4800.

I can figure out the appropriate pitch and such using the formulas I've already found here, but I don't have a clue as to what brand/model prop to even begin to invesigate.

The boat is a fairly heavy 19.5 ft 1979 open-bow runabout (Slickcraft). The holeshot is fine for me as it is, and I wouldn't cry if it lost some on that end. The boat is used mainly for cruising around and rarely pulls anyone and is rarely run at WOT. I'm looking to prop it for maximum fuel efficiency in the mid-throttle rage. I know I want to stay with SS.

So, the questions are: 3 or 4 blade, and what models and features should I be looking at?

Thank you for your help!

 

[Silvertip]

Re: New Prop for Mercruiser 260

First of all, forget the notion that you can prop the boat for better fuel economy by over propping it (lowering mid range rpm). Why doesn't that work you ask? Remember, the prop works like the tranny in your car or truck except it has only one gear. Think how gutless your vehicle would be having to start out in high gear all the time. Any saving you achieve at mid range would be eaten up just trying to get on plane not to mention the strain placed on the engine. If the prop is wrong at wide open throttle, it's wrong across the board. Prop it for WOT and economy will be the best you can get. To save fuel, throttle back, lighten the load by running with the fuel tank half full (if that's an option). Take less stuff with you. Have your passengers go on a diet (doesn't apply to you of course). Make sure the engine is tuned properly and that the hull is clean. If you like the prop you had but it simply has too little pitch, buy exactly the same brand and model but one with more pitch. Change brands and models and you begin the chase for optimum performance all over again because props of the same pitch from various manufacturers rarely perform identically. It's all in the design and design takes on many factors.

 

[MikDee]

Re: New Prop for Mercruiser 260

As a starting point, I know a Mercruiser Mirage 2 SS prop, works well with it's matching brand, but it is expensive! You need one of the local prop guru's like Walleye to help you out better here.

 

[MelLandry]

Re: New Prop for Mercruiser 260

Silvertip:

Thanks for the tips. I wansn't aiming to overprop. As I said, I can work the pitch/WOT out using the formulas here. As far as going from what I've got...the prop I'm running is so old and reworked, that I'm going to be starting over no matter how I look at it.

The tips I guess I'm looking for are things like 4 blade, 3 blade, cupped, vented, etc. The combination that will likely provide the most fuel economy on a properly propped boat for the use patters I outlined in the first post. Then perhaps a selection of brands/models that fit the suggested parameters.

MikDee:

Thanks for the suggestion. I didn't see a "Mirage 2" on the Merc site. I see a "Mirage Plus". Same thing? New model? I'm going to check it out.

 

[MikDee]

Re: New Prop for Mercruiser 260

Silvertip:

Thanks for the tips. I wansn't aiming to overprop. As I said, I can work the pitch/WOT out using the formulas here. As far as going from what I've got...the prop I'm running is so old and reworked, that I'm going to be starting over no matter how I look at it.

The tips I guess I'm looking for are things like 4 blade, 3 blade, cupped, vented, etc. The combination that will likely provide the most fuel economy on a properly propped boat for the use patters I outlined in the first post. Then perhaps a selection of brands/models that fit the suggested parameters.

MikDee:

Thanks for the suggestion. I didn't see a "Mirage 2" on the Merc site. I see a "Mirage Plus". Same thing? New model? I'm going to check it out.

Maybe the Mirage Plus is a new model? But not having any great info like this site years ago, and due to modern technology giving us a huge selection of different brand props, I found that I preferred the performance of Mercruiser props over Michigan wheel back then. The latter, seemed more suited for less speed, but more power in heavier boats.