TOPIC: 1958 Johnson Super Seahorse - lower unit

Looking for some advice... I need a 1958 Super Seahorse 35hp lower unit due to the fact that I messed up the upper part of my lower unit housing trying to drill-out the three screws for the water-pump impeller housing (lets just say the screws are still in the housing and all three screws now have new holes thru the aluminum adjacent to the screw shaft.. HA)

So, I have heard that I should not purchase just an upper half of a lower unit.. that the hole that the prop shaft comes out of was originally line-bored, and so, you should always purchase the upper housing and skeg together as a matched set.

How true is this? I think I can pick up a bare upper housing for less than I can get a whole lower unit for... and I have good internals and an excellent skeg.

Thoughts? Comments? Cheap housings for me to buy? haha.. thank you in advance for your help and assistance in this matter.

Andy

Yes you should try to get a complete LU. The bullet was cast as a complete part and then cut along the ridge to make the 2 halves. It is almost impossible to get a non matching skeg portion to seal up with another top section. I don't think line boring was used on these units.

The machining was done when assembled so they are a matched set.--Machined at 90 degrees to the driveshaft.--Precision stuff as no shimming is done on these.

Are you sure your are not giving up too early? There are a lot more experienced opinions available here than I can give, but these screw heads breaking off is a pretty common situation...
I would try filling the holes with aluminum epoxy, getting the surface flush with the pump cover again, have someone hold the cover in the right position, start with a drill bit same size as the
hole in the cover just to start a dimple in the exact center of the three holes, then start t drill with downsized bits until a tap can be run. You should be able to go a little deeper than the originals...
This might not work for you, but it doesn't cost...
If this type of work is not on your agenda, You might check with
a decent machine shop...Could cost less than a new unit...Ed

Too late to ask question now I suppose.----Many different ways to remove screws that will work just fine.

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Now it is time to make a " dummy water pump housing ".

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Make it out of say 3/4" steel plate.----Put a hole in it to clamp it through the driveshaft hole.----Put the correct size holes in it for the screws.----Clamp it in place and use it as a drill guide.

I do not think these housings were cast as one piece and split.

Thank you to all of you...I appreciate all of your recommendations! Hmm, my mind is now going with the aluminum epoxy idea! All that is required of the screws in the end is providing a seal for the water pump impeller.. and yes, everything else on the unit is decent..hmm.. I know for use that I'll be replacing with cap type screws rather than slotted or philips head.. might not be original, but sure a lot safer to remove when needed.

Thank you again for the input.. I think I might be able to lick this, but most likely will not get a moment to work on the bench and see for another month or so, due to spring obligations.

Andy