First, a big thanks for all the things I've learned here during the past couple of years.
The point of this: I finally got around to buying a new prop for my 2013 9.9 Merc 4-stroke and the rpms and mph went way up.
I bought a long shaft because it was on sale, in stock, and was $700 less than the local Yamaha dealer wanted for a 9.9. And I knew I wouldn't be using it often. There are 3 or 4 restricted hp reservoirs within an hour that we like to fish from time to time.
I bought a Grizzly 1648 in 2014 for largemouth fishing and we loaded it down with everything we wanted for comfortable fishing. A buddy used to be a semi-pro bass fisherman and we set up my boat similar to his beat up 20-year-old 16' Polar Kraft. He's owned a dozen boats or more including big, fast bass boats, but we like fishing quiet places using trolling motors.
My boat is a 2014 with a listed weight of 495 and deadrise of 3 degrees. They claim the transom is 20", but it's really 19.3" if you know how to measure a transom. That puts the Merc prop waaaay below the boat.
495# for the hull. Two of us at 200# each. Maxxum 70 24v bow mount. 3 61# batteries (2 on the floor near the front). Old trolling motor on the transom. Big box store carpet glued down. Thick aluminum hinged over the well in the back to increase the standing room. Two anchors, two nice seats, cooler, 20# of tackle or more. Junk. It's a hog, but the seat posts are 9' apart and the boat is really stable because it sits so low.
I added it all up once and it's still legal, but only with the two of us.
The original problem: With the weight and the prop buried, it would only do 5.5 mph. I bought a Tiny Tach and found it was turning 4500 with a max of 4550 sometimes. Hmmm. There was room to block the engine up an inch maybe, but it would still be 3" too deep.
The factory prop is 8.5 pitch. I read that going to the same prop in 7.5 would increase rpms by 200. Some folks said 300 or 350 per inch. Merc also makes a 6.5, so on a good day with any luck a 2" decrease would add 600 or 700 rpms. And that would take me to 5100 or so, just within the 5000 to 6000 range. What to do? I kept fishing electric and didn't run the outboard too hard.
So I bought a Merc 8.9 x 6.5 and went to the same reservoir with the same guy and gear and tank of gas.
Son of a gun. Now the Tiny Tach reads 5850 and 2 smart phones and my Lowrance Elite-5 HDI are all reading 10.7 mph. Well that's a pleasant surprise. The boat is almost peppy now and twice as fast. I might just take it out in the James River now if the current isn't to great and the tide is running the right direction.
When I went to get the trailer my buddy took a little joy ride - he said hit 13.5 mph. I guess I need to find some pics.
John
The point of this: I finally got around to buying a new prop for my 2013 9.9 Merc 4-stroke and the rpms and mph went way up.
I bought a long shaft because it was on sale, in stock, and was $700 less than the local Yamaha dealer wanted for a 9.9. And I knew I wouldn't be using it often. There are 3 or 4 restricted hp reservoirs within an hour that we like to fish from time to time.
I bought a Grizzly 1648 in 2014 for largemouth fishing and we loaded it down with everything we wanted for comfortable fishing. A buddy used to be a semi-pro bass fisherman and we set up my boat similar to his beat up 20-year-old 16' Polar Kraft. He's owned a dozen boats or more including big, fast bass boats, but we like fishing quiet places using trolling motors.
My boat is a 2014 with a listed weight of 495 and deadrise of 3 degrees. They claim the transom is 20", but it's really 19.3" if you know how to measure a transom. That puts the Merc prop waaaay below the boat.
495# for the hull. Two of us at 200# each. Maxxum 70 24v bow mount. 3 61# batteries (2 on the floor near the front). Old trolling motor on the transom. Big box store carpet glued down. Thick aluminum hinged over the well in the back to increase the standing room. Two anchors, two nice seats, cooler, 20# of tackle or more. Junk. It's a hog, but the seat posts are 9' apart and the boat is really stable because it sits so low.
I added it all up once and it's still legal, but only with the two of us.The original problem: With the weight and the prop buried, it would only do 5.5 mph. I bought a Tiny Tach and found it was turning 4500 with a max of 4550 sometimes. Hmmm. There was room to block the engine up an inch maybe, but it would still be 3" too deep.
The factory prop is 8.5 pitch. I read that going to the same prop in 7.5 would increase rpms by 200. Some folks said 300 or 350 per inch. Merc also makes a 6.5, so on a good day with any luck a 2" decrease would add 600 or 700 rpms. And that would take me to 5100 or so, just within the 5000 to 6000 range. What to do? I kept fishing electric and didn't run the outboard too hard.
So I bought a Merc 8.9 x 6.5 and went to the same reservoir with the same guy and gear and tank of gas.
Son of a gun.
Now the Tiny Tach reads 5850 and 2 smart phones and my Lowrance Elite-5 HDI are all reading 10.7 mph. Well that's a pleasant surprise. The boat is almost peppy now and twice as fast. I might just take it out in the James River now if the current isn't to great and the tide is running the right direction.When I went to get the trailer my buddy took a little joy ride - he said hit 13.5 mph. I guess I need to find some pics.
John
