impeller work

has anyone heard of machining down a 6 7/8" auger to lighten it down to increase holeshot and topspeed I have heard it being done on merc 60/40 just curious if anyone has tried it and how it worked out

How would that work? It would still be moving the same amount of water.

What they are doing is machining out the inside of the impeller to get more volume of water at take off

I think you would loose top end with less mass and may cause deformation.

lemi said:

What they are doing is machining out the inside of the impeller to get more volume of water at take off

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I can't imagine that amount of increased volume(<2%) would make any difference.

What do you have? four stroke 60/40 of some kind? Mercury/quicksilver who are the ones that make the three blade 6 7/8 stainless impellers. The new ones they make have been machined differently to allow the new 60/40 four chokes to be able to spin up to their optimal rpm range. THis is because the 60/40 four chokes didn't have the power to spin the old style non cut back stainless impellers in there optimal rpm range. So if you have an old style stainless impeller that isn't one of cut back ones don't cut it back sell it to me and go buy a new impeller that is a cut back one meant for a four choke. They're was thread with pictures of the two style 6 7/8 impellers that show the difference.

This is the one to look at to see the difference in the impellers they no longer make the two stroke style one merc simply started machining the impellers differently for four strokes and kept the same part number.

https://www.forum.tinboats.net/viewtopic.php?f=85&t=42764

So if you have an old style one don't machine it just sell it to a two stroke guy and buy a new one off ebay this is the best price I have found for a new one that would most likely be a four stroke one.

https://www.ebay.com/itm/BRAND-NEW-OEM-MERCURY-MERCRUISER-IMPELLER-PART-47-855708T60-/262771660180?epid=2113606538&hash=item3d2e695594:gAMAAOSw6DtYWfbK&vxp=mtr

what some guys have done is polished their impellers and housings to make water flow better which can be good sometimes for a 1-3mph gain on top depending on how rough the castings were to begin with.

I had the inside of my auger machined out and it has not been polished . I have gained 5 mph . also have heard of folks using those tornado nuts on the augers . I am running a 2017 merc 60/40 on a 1852 blazer . my top speed up river is now at 30mph

lemi said:

I had the inside of my auger machined out and it has not been polished . I have gained 5 mph . also have heard of folks using those tornado nuts on the augers . I am running a 2017 merc 60/40 on a 1852 blazer . my top speed up river is now at 30mph

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I stand corrected. How exactly does this work and what is a tornado nut?

Tornado nut is a acron type nut to replace factory nut seems to cut down on turbulence in pump

I have seen folks running a 7 3/16 in a 60/40 merc 4s running pretty darn good
I think there are a lot of tricks out there if a guy is willing to play with them

lemi said:

I have seen folks running a 7 3/16 in a 60/40 merc 4s running pretty darn good
I think there are a lot of tricks out there if a guy is willing to play with them

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Sorry but I'm calling BS. Maybe on a built 2 stroke 60/40 merc but not a 4 stroke. They can't pull a standard 6 7/8" up to rpm let alone a 7 3/16"
Lightening the inside of the might help some with throttle response but it won't cause it to pick up more water. Your removing material from the inside of the cone where the holes are drilled for balancing so it has no effect on how water flows.
The twister/tornado nuts do help with turbulence but it's not going to gain the average boat much if anything that they can feel, but every bit counts when your racing.

You might say bs but I have seen it work like I said if folks are willing to experiment how knows what can be done for I have seen several 7 3/16 augers in 4s

I am turning 5500 before and after auger work
My boat has never bounced but I trim it will now

So how many rpms are these 4s with 7 3/16" turning? You said you had impeller work done, did Terry do your impeller?

Terry did not do my auger I am running a 6 7/8 terry is doing the 7 3/16 I don't know what rpm they are running any boat I have been in that is running that auger has had no rpm gauge but seems to be turning pretty good

Y'all talking about Terry Weaver? He cuts the impellers back, polishes them and polishes the liner. $150-$200 in work and lots of guys claim they are getting 3-4MPH out of the 60/40 4 strokes.

Y'all can call BS but this guy can work a pump. Check out SEMO jet boat enthusiasts on facebook.

Yes terry has done several boats around and has had success . He is running the 7 3/16 auger in them

Some guys have also lost MPH after he worked on the, myself included! So, don't count your chickens before they hatch! Better listen to Lil Blude Rude