twin 67

[aaron alberico]

hi guy's just wondering how the 67's compare to twin 80's and 90's.

is there much differents in speed, handling, what props would u run, only got twin 80's and 90's downunder.

 

[Don Ferrette]

Well it's kinda like this, I have not seen a twin 67 around here mainly because they would have to run against the twin 80's & 90's in the same class & as the saying goes there's no substitute for cubic inches. So my question is this- do you already have the motors?? :unsure:

 

[TimD]

Aaron,

A few people ran 67's in twins up here but quickly upgraded to larger engines. There are plenty of 90 powered twins here.

I still think you are twice as likely to DNF :lol: Build a single - if your 67 is anything to go by it will be fast enough - just make it a rough water boat.

Tim.

 

[shoboat]

Aaron,

Twin 67's used to be normal over here,but now most are running 84's

or 90's in their twins. I think the power is unbeatable for a 67 to compare

to an 84 or 90. Prop wise the 67 just won't turn the pitch that the 90's do.

Looks like you did well at your last race,did you get to see any of my props?

Thanks,

Mark Sholund

Props-4-U

 

[Ian Inverarity]

Aaron,

I have been thinking about this and I think you would be better off with twin 80's. The motors are the same size, so there is no weight disadvantage for you. And a bit more capacity and power can only be better! Even if you have a couple of 67's, for a twin you want everything exactly the same spec, so you have to dedicate two motors for it anyway.

Pity the rules dont allow me a twin A100 boat...

Nitrocrazed racing: 17.2cc vs 30cc

 

[EatMyShortsRacing]

Just you wait till I get my 8 MAC 21s running in synch!!!!

EMS Racing Now THAT would be a WIDEBOY tm.

 

[Don Ferrette]

" Just you wait till I get my 8 MAC 21s running in synch!!!!"

:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:

 

[Mark]

Nitrocrazed,

I think it would be interesting because as you mentioned 84's have more capacity and power, however you also need to carry more fuel. You might be able to get away with running lighter driveline as well. Just a thought.

 

[aaron alberico]

guys just want to be different, i wanna give the guys with there twin 80's 90's a run for there money, like Tim said if i get a twin 67 to go as quick as my single watch out....

 

[shoboat]

Aaron,

I doubt if your 67's will keep up to twin 84's or twin 90's.

Remember " Nothing Like Cubic Inches " You will have fun trying though.

From a propeller standpoint you will not be able to pull the bigger pitches

for the all out speed and acceleration.

Good Luck,

Mark Sholund

 

[ClayGlover]

how 'bout that! I thought it was worth noting that Lenny Blake won the multi class with a twin .67

 

[Preston_Hall]

I wouldn't say that cubic inches is the key. I have seen 21's, 45's, and 67's faster than 80's. SETUP!

 

[AWaddle322]

Remember when you talking about 80', 82's, and 84's they are nothing more than a 67 case with some minor change to make them a bigger motor. What I am trying to say is a manufacture starts off with an 67 that is optimized hopefully and then unoptimizes itto make it something bigger.

you may be able to pull a bigger prop with an 80 than you can with a 67 but the rpm goes down. When it is all said and done and you have setup both boats the best they can be set up you will find the speed about the same. One does it with rpm and the other does it with bigger prop.

With 90's and 91's they are so heavy and rpm limited they are at a disadvantage as well.

As Preston said it is all about set up. I know of a certain boat manufacture that believes that twin 45's would be the ultimate and I believe that he may very well know something that the rest ofus don't. He swears if Picco blackhead 45's ever become readily avaliable that he will build a couple. This person has mutliple US1 as well.

If I ever decided that I wanted to race twins again, it would most likely be with 67's. Twins are about reliabality and I beleive that a 67 is more reliable that its punched out cousin. Not to mention have twice as many 67 as I do all other sizes combined.

 

[Tim Kish]

As for speed I agree with Preston very little difference.

I think the twin 67 may suffer a little more simply because it would lighter than a twin 90 and those twins make monster sized holes that make the water very tough

on light boats.

Tim K

 

[Mike G]

That was a twin 67 that just won the NAMBA nats!

 

[TimD]

I'm with AW on most of the comments and want to plant an idea.

Most of the 90 engines out there are drastically RPM limited compared to the smaller engines.

What if a 90 sized engine could pull the same rpm's as the 67s and 80's but with more pitch? Faster?

 

[Preston_Hall]

90's aren't really limited on RPM's. Kentley's Orlic/CMB 90 sings like a 21. Of course that is the only one I have heard twistiting the cat's tail.

 

[TimD]

Consistently revving a CMB 90 to over 22000rpm is just asking for trouble IMO. The crank design isn't up to sustained high rpms. The CMB makes a lot of torque and almost everyone utilises the torque at lower revs with big props.

I assume the crank in Kentley / Frank's motor has had some work in this area?

Tim

 

[EatMyShortsRacing]

Tim,

Wait till my twin A90s hit the water again

EMS Racing there is no substitute for cubes!!!

 

[AndyBrown]

Looks like all the twins at the NAMBA Nats where set up for cosistancy.

The fast heat time fo Twin Hydro was 1:14.

45 Hydro was 1:12

67 Hydro was 1:09

X Hydro was 1:07 with a single 80.

We've built SG's with Twin 67's that were very fast, but the Twin 84's have been consistantly 3-5 mph. 80-84 engines are a few grams lighter than 67's if that means anything.