wanting to convert 1979 15 hp to long shaft are all parts interchangeable

[storedaddy]

I have seen several kits and lower units at a fair price. what years are interchange able with this unit? are all omc the same? and is this an easy thing to do myself how much would a shop charge to add an extention or change the lower unit if I supply the parts? I have been offered an extention kit from a late 90's 15 hp. is it easier to just change the whole lower unit or to add the extention. I know this is alot of questions but I would appreciate any help I can get on the subject.
thanks, Iboats has been a great help don't know what I would do without you guys.

 

[noelm]

Re: wanting to convert 1979 15 hp to long shaft are all parts interchangeable

not all motors are the same, the biggest problem you will face if you do the extension yourself is the driveshaft replacement, you need to dismantle the gear case to replace it, if you could buy a complete lower assembly from the same model it will be quite easy, as long as it comes to bits without too many broken bolts.

 

[bktheking]

Re: wanting to convert 1979 15 hp to long shaft are all parts interchangeable

not all motors are the same, the biggest problem you will face if you do the extension yourself is the driveshaft replacement, you need to dismantle the gear case to replace it, if you could buy a complete lower assembly from the same model it will be quite easy, as long as it comes to bits without too many broken bolts.

No you don't have to dismantle the gear case to add an extension and the gearcases for the 2 strokes are the same from 74 up, you will need to pull the lower unit off and simply pull the driveshaft up and out of the gearcase.


A proper kit will require the following:

extension to take it from a 15in to 20
water tube extension which is a small length of copper tube (5 inch, you could make your own buy buying 3/8 copper with a copper coupler and the gear to solder copper) longer drive shaft, again will take it from 15-20.
and 6 bolts to add the extension
shift rod is longer

read http://www.sschapterpsa.com/ramblings/OMC-Converting_shafts.htm

In my case I found a sail lower unit and bought it with the water tube and driveshaft. I didn't need to replace the shift rod as the sail shaft already has the lower shift rod at the right length.

 

[bktheking]

Re: wanting to convert 1979 15 hp to long shaft are all parts interchangeable

and is this an easy thing to do myself how much would a shop charge to add an extention or change the lower unit if I supply the parts? I have been offered an extention kit from a late 90's 15 hp. is it easier to just change the whole lower unit or to add the extention. you guys.

Yes, it would take you an hour or so with a couple of wrenches and a straight screwdriver. A 90's 15 kit should fit according to the Machinest, the gent who wrote the site I referred you to. It is easier to install the kit than to install a longer lower unit. To do it right the water tube needs to be extended with the proper tube and changing out a water tube requires the powerhead to be removed.