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Swapping out 470 for 120

T

tobra100

Member
"could sure use smoe help moun

"could sure use smoe help mounting transom plate,
1.the 120 hp transom plate does not line up. I'am trying to bolt it up to the existing gimbal housing which ia a 1986 rinker with an alpha drive. and its existing gimbal housing. the bolts coming thru transom are in a different place. Does this mean that I have to use the older gimbal housing,fill,and redrill the holes that wont align?
2. Will the alpha drive spline go into the 120 HP coupler or will I run into problems there also? 3. Is the power trim wiring that runs thru the transom plate hard to replace? Its kinda frayed...Any help would be appreciated. Ray...
also?"
 
that's a drop in HP.. well

that's a drop in HP.. well I think you'll need a new drive spline as I think the 120 used the longer one. spline and size wise it's the same.
 
Different gearing in the leg.

Different gearing in the leg. Original ratio; 1.98:1 for the 120 and 1.84:1 for the 470. Might throw your performance off a bit.
 
"Ok I got some clarification t

"Ok I got some clarification the 4 & 6 Inlines are all the same ( i used a 120 on my 74 165 6cyl so I know that's Ok ) but an example here..

https://www.marinepowerservice.com/BoatingStore/browse_detail3.cfm/productID/426 79.cfm

58858A1 58858A1 U-Joint Assembly Fits IA/IB/IC EZ Shift & MC-I (in-line engines) (1964-1982)

I think they changed it in '83, cuz

14 59830A7 --YOKE ASSEMBLY, COUPLING END (click here) is for R/MR/ALPHA ONE (Sterndrive) 1983-1990 6225577 THRU 0D469858

14 39385A1 --YOKE ASSEMBLY, UNIVERSAL JOINT-COUPLING END(IN-LINE ENGINE) is for 120/140 1978-1982 4893635 THRU 6225576

Not sure if can use the alpha shaft, if it's too long or not, It might be OK with the 120 gimbal and transom housing or not.. The depth is the key I know the splines are the same, wont know till the engine is in and you put the drive on and put some grease on the shaft and see how much spline depth you have.

165-120hp is about a 10mph loss.."
 
"Brian The ser # on the motor

"Brian The ser # on the motor is 1829658 . Where would I find the numbers on the yolk assembly? also if I need the numbers on the alpha drive, where would I find them? Ray"
 
"BRIAN, Also, can you shed a

"BRIAN, Also, can you shed any light as to why the yolk (hole Pattern) is different. Can I fill in the center holes on the transom and re-drill? Thanks again for the help...Ray"
 
"No serial numbers on the gimb

"No serial numbers on the gimbal/yolk assem.. only numbers on the port side about half way down of the top or drive shaft housing.

Dont know why the patterns is different guess merc never thought people would change from I to alpha or vice versa, i've read others swapping from I to alpha but never read anyone post about differnce in the hole spacing, dont see why you couldn't fill the holes and drill new ones, I'd be concerned about weakening of that area, is the wood in that area strong ?

What are you going to use to seal the housing to the boat? Do you have a new gasket seal ?"
 
"I saved the old broken gasket

"I saved the old broken gasket, I was going to the Merc store and see if they can match it, Do you have any suggestions? Did my ser. number help to see if I have the right spline. Would you know how hard it would be to replace the trim wiring that goes thru the transom, into the gimbal housing? thanks ray"
 
to replace the trim wiring you

to replace the trim wiring you typically need to remove the bell housing or helmet. If your 120 serial # is 1829658 its pre 1967.

120/140 1967-1969 2062141 THRU 2791956

What info do you have on how good this engine and associated parts are ?? I'd be a bit nervous.

I have access to some transom gaskets for 1963 to 1973 Merc # 27-70974 fits all from 1963 to 1973

Let me know.
 
"I dont know how it runs i&#39

"I dont know how it runs i'm taking a big gamble on it. Everything looks in good shape though.
Like I say, I got everything with the motor up to the leg. He sold the leg separate."
 
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