early Xflow gearcase ratios

[Umassot50]

I have an OMC 73 135hp gear case and a 73 115hp gear case. do these two lowers have the same gear ratio or different? i checked the gear part numbers and they are all different. logic would indicate if their different the 135 would have the numerically lower gear ratio. is that correct? anyone have a list of gear case ratios by year and HP size for 70's Xflows?

[David]

The oldest brochure i have is 1978. All V4s were 2:1 that year.

[Baja16]

I just looked in our 73' service manuals and and they should be the same (2:1)... but the books technically say the 85hp and 135hp are 13:26 and the 115hp is 13:25, I bet its a typo... and should be 13:26 like the rest...

[JWTjr.]

the oiler-style units on the 135 were 1.92:1 (13:25)...

[Umassot50]

whats an oiler style unit? how do you account for the gear sets having different part numbers for the 135 and 115?

[ChrisCarsonMarine]

An oiler unit is called so because it uses an oil pump run off the forward gear to power the shift mechanism,this unit,1973-1976,was properly called 'powershift',the 85 had a 4 spline driveshaft,the 135 had 20 splines,most likely thats where the gear differences came from,chris

[194268]

When I started at Evinrude way back in '68. And when the 1969's came out, all V-4 crossflows where 2:1 from that point on.

[Umassot50]

well thanks guys. I just went and checked out both cases. the 135 unit does in fact have a 1.92:1 ratio. I marked both shafts and props and spun the props. the 135 unit was consistently less than 2 turns of the drive shaft for 1 turn of the prop checked visually by my marks. the 115 unit was dead on at 2:1

[JWTjr.]

From 73-76 the 135s all had 1.92:1 gears. The 77 140 had them too, but used a newer style case with swept skeg. The 1978 140s changed to a non-oil-pump unit and 2:1 gears, and they stayed that way until the end of the crossflow V4 production.

Tiger

[Umassot50]

good to know glad i figured this out. i had been using the 115hp 2:1 unit on my boat previous. the 1.92:1 will give me better prop selection turning a smaller pitch faster is easier than getting a bigger pitch some times with the small gear case.

[powerabout]

From 73-76 the 135s all had 1.92:1 gears. The 77 140 had them too, but used a newer style case with swept skeg. The 1978 140s changed to a non-oil-pump unit and 2:1 gears, and they stayed that way until the end of the crossflow V4 production.

Tiger

Correct
in a light boat they were faster and with the huge compression ratio and short induction they had tons of torque

[terry taylor]

good to know glad i figured this out. i had been using the 115hp 2:1 unit on my boat previous. the 1.92:1 will give me better prop selection turning a smaller pitch faster is easier than getting a bigger pitch some times with the small gear case.

HI. Myself I really don,t think .08 per revolution will amount to anything significant thanks.

[Umassot50]

right its not much, but it will decide which gearcase i rebuild and LWP cone over the winter for a project

[terry taylor]

right its not much, but it will decide which gearcase i rebuild and LWP cone over the winter for a project

I forgot to add if they are different in spline count, 13 is best and knowingly prop selection thanks.

[194268]

MMMMMMMMMM 1.92 ratio on the 135's, well I've been wwwwrong before. But I can't remember is the second or third time??????