I need help! On installing a foot on a Mercury 80hp Thunder bolt 1969

[evangelistrr]

I have a 1969 Mercury 80hp thunderbolt I am installing a replacement foot in it. The foot is off a 85 hp Mercury with blue strip.. The foot and the motor are both in Neurtal, when I insert the foot I can not get it to go all the way in.. I notice that there is a pin at the top of the shaft of the replacement foot but there is not on located on the on that came out.. What is this pin for? And why does the 80hp foot dont have one and do I need to remove it?

This is the last step before we can have this beautiful boat on the water. Please any help at all we be great.

Robert

 

[Chris1956]

Re: I need help! On installing a foot on a Mercury 80hp Thunder bolt 1969

The pin on the end of the driveshaft is a bearing preload device. Not all mercs have them, however, it does not affect the compatability of gearcases, on it's own. I do not know if the two gearcases you are trying to swap are interchangeable. They may be, or may not be. The Blue stripe motor was likely a mid -1970 model?

Are you turning the flywheel to align the driveshaft splines with the crankshaft splines? Can you see if the shift shafts are mating? A lot of times the shift shafts are not well lined up, and you need to move them so they can align.

 

[evangelistrr]

Re: I need help! On installing a foot on a Mercury 80hp Thunder bolt 1969

So the way I read your reply is that the pin on the end will not stop it from going all the way in so you can mount it. I have both the engine and the foot in netuarl.. We slide it in and it is not giong all the way in so..\

 

[Gomer50]

Re: I need help! On installing a foot on a Mercury 80hp Thunder bolt 1969

Chris is right the preload pin was introduced somewhere in the early 70's when Mercury switch to roller bearing style bearings on the driveshaft,on the 69 Mercury the one piece ball bearing style was used on the driveshaft.If not mistaken the preload pin was to keep some pressure on the roller bearing when installed.Both will work on your motor.The trick is to get this all lined up,water tube,shift shaft,and the drive shaft.Not to be funny but once you done this a couple of times it gets easier.Also the 1969 used a 2:3 gear ratio and in the mid 70's 85hp Merc's ran a 2:1 gear ratio which means you might have to drop a couple of prop pitch sizes to keep your motor whithin its rpm spec.s.

 

[evangelistrr]

Re: I need help! On installing a foot on a Mercury 80hp Thunder bolt 1969

Do I needto remove the pin for it to go in to place? If so will it trwist off are will I need to cut it off?

Chris is right the preload pin was introduced somewhere in the early 70's when Mercury switch to roller bearing style bearings on the driveshaft,on the 69 Mercury the one piece ball bearing style was used on the driveshaft.If not mistaken the preload pin was to keep some pressure on the roller bearing when installed.Both will work on your motor.The trick is to get this all lined up,water tube,shift shaft,and the drive shaft.Not to be funny but once you done this a couple of times it gets easier.Also the 1969 used a 2:3 gear ratio and in the mid 70's 85hp Merc's ran a 2:1 gear ratio which means you might have to drop a couple of prop pitch sizes to keep your motor whithin its rpm spec.s.

 

[Chris1956]

Re: I need help! On installing a foot on a Mercury 80hp Thunder bolt 1969

I think you need that pin for the bearings to work properly. The question is whether that gearcase will work with your older motor. I just do not know that answer. Have you mated the driveshaft splines? Are the crank splines in good shape? Have you mated the shift shaft splines?