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'58 Lower Unit Won't Drop

5

58 Lark

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I started to replace the impeller on a 1958 35 HP Evinrude Lark, but the lower unit won't drop - I can only get a hairline of separation. I tried wood wedges to no efect.

I have removed the lower drive linkage bolt and four of the six lower housing bolts. The heads on two of the lower housing bolts sheared off.

Suggestions for getting the lower unit to drop and best solution for removing sheared bolts from aluminum castings if I succeed in getting the thing to separate?
 
Put the hammers and wedges away !-----------Is there a rear cowling hiding it !------Have you looked at a parts diagram for your model ?
 
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Item # 7 in lower unit group and listed as item 12 in swivel bracket group.-----------Find it and remove it !!!!----Get a 9/16" wrench ready.
 
Simple. You have to remove the rear cover that covers the midsection (whole bunch of screws). Ah-hah!!! There is the bolt.
 
#7 (Short Shaft) or #70 (Long Shaft). You can't see it till you get the rear cover off.
 

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No need to break any bolts....you should be using a propane torch and patience as you thoroughly heat the aluminum around any bolt that doesn't easily come out. Concentrate the point of the flame on the area you are heating and don't force anything. Give the aluminum a long period of time to absorb the heat. Aluminum has what is called a high coefficient of expansion when heated and if the proper procedure is used, you will not break any bolt.
 
10-4. The philips head cowling bolt heads were wallowed out before I started so this is going to take some patience - not happening tonight.

I had already used too much force removing the lower unit bolts and two of the heads sheared off. Any recommendations for removing the bolt shafts embedded in the aluminum casting.
 
What I do is drill a small pilot hole all the way through the broken bolt and squirt some power steering fluid into the hole and let it sit overnight Get a reverse spinning drill a little smaller than the inside thread size of the bolt. The next day heat the housing up just enough to make the power steering fluid bubble dont burn the paint and then with your drill in reverse use alot of pressure and slowly drill the bolt out. When it gets a good bite it will likely just spin the bolt out for you. It is important to center the pilot hole in the broken bolt good so you dont damage the threads in the housing much. Power steering fluid is the best liquid wrench I have found for corrosion it dont dry out like PB or WD.
 
If the broken bolt or screw has a 1/4 inch or more sticking out, using heat and vise grips should do the trick. Sears sells the reverse bits should they be needed.
 
Success!! - thank you everyone. I have a few followup questions:

1. The Clymer manual says to coat both sides of the impeller plate gasket and the impellor housing bolt threads with with OMC Gasket Sealing Compound. Is there a more readily available substitute for the OMC Compound? The local Advance Auto parts has Permatex 80019 Aviation Form-A-Gasket No. 3 Sealant.
2. Clymer manual says to lubricate several parts, including o-ring, with with OMC Premium Blend Gearcase lubricant. Is any name brand outboard gearcase lubricant fine?
3. Clymer manual says to coat outside diameter of water tube grommet with Scotch Grip Rubber Adhesive 1300. Is there a more economical alternative for this product?
4. The very tip of the cavitation plate (stern) is broken off - a ragged area about 1/4" in diameter. Could the damage divert air into the water intake or otherwise impede performance?
 
1. There is no plate gasket. But the #3 will be just fine where the plate sits on the gearcase
2. Yes
3. Not even necessary
4. Nah.
 
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