[QUOTE=Nice Pair;4490404]I've been running twin outboards for about 15 years on different boats and have seen the motor with the counter rotating lower consistently turning 200+/_ rpms slower.

I've always believed the difference to be the way the lower handles the thrust. (front tapered cone bearing R.H.) (flat needle thrust bearing L.H.)
The counter rotating also runs hotter and will "burn" the oil faster.

x2 as ive been racing merc v6s since 1981
and believe the same as with gearcase running on reverse gear for counter
the differences in the bearing,the heavier carrier,gears thrusting propshaft towards bullet as prop is pushing it the same direction
causing that bearing to be loaded harder and thus does burn the gearcase oil faster,,,,,
2 motors never run exact same so always put stronger powerhead on counter
adjust throttles on clock with a tad of slack so at speed throttles are even to even rpms
can even tweak a tad more load on the clock prop to sync in the 2 motors

It's nice to see running @ that speed that you wear your safety gear , Not to many would do that when running there boat to the limit , GREAT job :)

How did you know Steve? :confused: You always catch onto my tricks......

Thanks, when I'm out testing by myself, and no buddy on the water in another boat, I'm extra cautious. I have all my race gear, so I figure it's stupid not to wear it - even if a chute jacket is a little overkill at only 120mph.

Now to get this thread back on track, Steve just ran 115 today in his beautiful blue bomber! Congrats Steve, now post up on here to tell everyone about it. :eating:

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Thanx Dale for staying on top of things. Ha. I ran out today and ran this 115mph at 6940. Took a while to get there. Was great to finally break thru. It was with my Merc 33 pitch props. It was in the 70s here today and I was carrying about 50 gallons on board so its not a totally unrealistic number. What you can't see in the vessel view is my port motor is somewhere around 7100rpm and my starboard is around 6800 rpm. The port doesn't have much more to give and the starboard is lagging behind once again by roughly 300rpms. As I said before the marina is gonna start to try and figure out why that is happening. If I gained that back I would think I would gain a couple mph for low maybe 3mph would be great. Wont know until if or when that happens. If I had two strong motors Id bet they both be running on the limiters at 117 or 118mph. Nice to dream about. Ha. My Dewalds get back to me the end of this week. Dave took a little bit off the Dia and cup which he had left a good amount in. Im sure they will have to go back to him at least once more before they are tweaked enough. He's thinking the speed will come with the rpm increase. Once again my Dewalds are 34 pitch 15.25 dia and 20 degree rake.

That's great Steve. Hope they find something. It will be interesting to see also if the dewalds are 300rpm down also. I had a set of props once that one of them were way out of whack once they put them on an anylizer and checked the pitch of every blade.
It is possible they could have changed when the blades are thin.

Hey Ron. Already ran the Dewalds once thats why theyre goin back to be trimmed a bit. Need more rpms. When i ran them they also showed a difference in rpms. Not as much cause i couldnt up to the high end range. They start to separate at 6000rpms and it gets worse the higher you go. My girlfriend videod the vesselview a little while ago and we stopped it at different speeds to see where its off. At the top one motor was at 7100 and other at 6800 roughly.

maybe he can shave down the weaker motor prop a bit to get it to come up 200 or 300 rpm vs the strong motor prop ?

[QUOTE=johnmiffco;4490459]Hey John Thanx for the info, It does make sense. I believe when Skater tested that last 318 the motors were turning very close to one another. Much closer than my 300rpm difference. At any rate Im gonna have it looked at because my mechanic said that 300rpms is a bit much to be off. He is a racer and throttles for one of the I/O Cat teams for years now. Thanx again, Steve.