'88 JohnnyRude 60 vs 70 carbs

[JB]

I noticed in the OEM Manual instructions for servicing the carbs that the carbs on the 60 have a low speed mixture adjustment and the 70s don't.

That makes me think they are different model carbs.

Anyone know if the venturi diameters are different?

 

[Dhadley]

Re: '88 JohnnyRude 60 vs 70 carbs

We went thru this a number of years back on a buddy's 70 on a Whaler. They used so many carbs on the 3 cylinder motors it gets pretty confusing. In 1988 the 60 and 75 were 49 cid motors and the 65 and 70 were 56 cid motors.

According to my stuff the 75 was the only one with the adjustable idle jet. The carbs on the 60, 65 and 70 are newer generation numbers than the 75 carb.

Now, in 1988 the 70 was one of, if not the best selling motor they had. We know they were running the 65 & 70's as lean as possible to pick up EPA credits quickly. With that in mind it seems those carbs don't flow as much fuel as the older carbs.

The 1988 75 carb has an older generation number and the 75 was the APBA legal motor for SST60. Those things make it seem the 75 carb that year would flow more fuel.

If I remember correctly we used a set of newer carbs on my buddy's motor. The older carbs like on the 75 produced a little more top end but he was mainly concerned with pulling the kids on water toys and skis. The newer carbs had more "punch" and didn't burn quite as much fuel. I do believe there was venturi differences but it wasn't much.

The bottom line is that the older style carbs flowed more fuel and were better suited for top end. Are you just looking for more rpm?

 

[JB]

Re: '88 JohnnyRude 60 vs 70 carbs

Okay, Dale, I think I see the confusion.

I was looking at a manual for the '89 60 and 70 "CE" engines, though mine is an '88 60 "CC". I was assuming (with all the risk that entails) that I have a 56cid engine and it was identical to the 60 "CE". From what you tell me I have a 49cid engine.

I was looking for a possible increase in flow from a larger venturi. . . maybe to get the torque curve of the 70.

It looks too complicated to mess about with it. I will put this '88 60 on my RED SKY (1986 Boston Whaler Striper 15) to replace the 48SPL on here now. The switch has more to do with getting OEM PT&T to replace the CMC 130 tilt and "trim" unit than getting more speed. I think calling that CMC a trim unit is very misleading.

Being able to go faster has never affected my success with the fish, anyway.

Thanks for the excellent and helpful info.

 

[Dhadley]

Re: '88 JohnnyRude 60 vs 70 carbs

The carbs will all interchange. Do you have other carbs? I'm thinking that we could get the carbs that are on the motor to flow more with some jetting.

Just an FYI -- the 49 cid blocks have 2 plates and a cover over the exhaust. The 56 cid motor only has a cover. IE -- if there's a bunch of plates and gaskets, it's a 49. 1 plate & 1 gasket, it's a 56. Both are pretty darn good motors.