6r74c prop choice differences

[crosbyman]

6hp Motor came with a 2 blade white plastic prop 8 x 7.25 inches

I have a spare 9.5hp 3 blade prop aluminum… 8 x 7.0 inches which fits nicely ( pin drive) on the 6hp shaft

would my 3 blader be a better choice on my rig ( 17.5 feet e/w 75 etec) _ ❓ if I swap my 9.5 for the 6hp as my preferred kicker for trolling

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[frankr]

You realize of course that is not the stock 9.5hp prop? As for which is better for your situation, try each and see what the results are. The 3 blade will give more blade area for more thrust if you have the horsepower to turn it. But it may present such a load on the 6hp engine that it can’t rev up to it’s potential. Try, see, and report back. My money is on the stock two blade. But I’ve been made a monkey of before.

[outbdnut2]

Since you are just using it as a trolling motor alongside your 75 HP, you probably don’t care about wide open throttle performance, as it’s not going to plane the boat off anyway. Given the size of the boat, I’d use the 3-blade – it will grab more water and function better in a wind at trolling speeds. I have used a 6 and a 7-1/2 HP motor on a fairly heavy, wide, deep 16′ Aluminum boat for fishing that we get free to use when we rent a 58 foot houseboat on Lake of the Woods in Canada, with no other motor on it. I believe this boat is rated at 40 HP max, and is driven at the tiller. When back-trolling for walleyes against a wind, 2-blade props do not work well. When you have to rev the motor up some while backtrolling against wind and waves to maintain the 1 or 2 MPH trolling speed, the 2-blade props gets to a point where they lose their grip and the motor cavitates, where 3-blade props work much better. If all of your trolling is going forward, the 2-blade will likely work OK, but I’d still go with the 3-blade for a better grip of the water. At low to medium RPM trolling speeds, propeller pitch doesn’t mean a lot.

For the last several years on the same trip, I now use a late 1980s 15 Johnson (of course with a 3-blade). It back-trolls as well as the smaller motors, but gets me up between fishing sports faster on the remote portage lakes I run them on.
Dave

[crosbyman]

Outbnut2.. Good points… thanks. My 6hp will be used for mostly trolling and hopefully never… to get me back home if the ETEC breaks down

I am not planning to row that rig back to shore if the ETEC konks out . that little 6hp may also vibrate a bit less than the 1966 9.5 which did not come with vibration dampners found on later version.

I kind of fancy this nice find over my turtle because it will sit a bit higher out of the water . I am always worried a big chop will flood that low sitting 9.5 … not that it has happened yet but I have been in rough enough waters to crack my oil tank (bad seams) on my ETEC a few years ago although at he time I did not have the 9.5 riding along the big guy.

F.R. You are correct, that 9.5 prop was in fact a "spare prop" purchased for my 9.5 because a local dealer was dumping his OMC/BRP stock of parts and the price was ok for me. Props are not cheap up here in free Medicare land.

i’ll get some last pics out with the finished electricals . the gearcase had clean oil, no mono spun into the prop shaft seal 🙂

lake trials can only start late April 😥

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[outbdnut2]

I agree you will like the smooth idling of the 6 over your 9.5. I have a 1969 9.5 that has the vibration dampers – the powerhead still shakes a bit, but it doesn’t get transferred outside of the enclosure. I’d take my 6 for trolling any day over the 9.5. The 6 can also be rigged for remote controls if you choose to without the cumbersome, but very nicely functioning aftermarket remote adapter for the 9.5 (which my 9.5 has).
Dave

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