Johnson 20 hp exhaust cover screws seized

[davedublin]

Hi guys - I'm new to this forum and I would appreciate your expertise.

I have a Johnson 20 hp, mid- to late 60s. After many decades of faithful service, the impeller in the water pump spun on the key on the prop shaft, the pistons nipped up and I am doing a complete engine refurb.

I have a block from other engine that is serviceable, and I want to make sure all is OK before I proceed with other work. But I am looking at those pesky exhaust cover screws, some of which are well seized. To make matters worse, they are slotted screws, not the hex heads on the later models. From the look of some of the screw heads, the cover has probably never been off. I had a big fight getting all the bolts off the lower unit to engine block and I'm not looking forward to getting all these screws off.

In your experience, is it really necessary to remove the exhaust cover? I am only thinking to check for blockages, as I don't want it overheating in this area. If it flows water OK, would this be enough?

Dave
Dublin, Ireland

 

[gm280]

Re: Johnson 20 hp exhaust cover screws seized

Hi guys - I'm new to this forum and I would appreciate your expertise.

I have a Johnson 20 hp, mid- to late 60s. After many decades of faithful service, the impeller in the water pump spun on the key on the prop shaft, the pistons nipped up and I am doing a complete engine refurb.

I have a block from other engine that is serviceable, and I want to make sure all is OK before I proceed with other work. But I am looking at those pesky exhaust cover screws, some of which are well seized. To make matters worse, they are slotted screws, not the hex heads on the later models. From the look of some of the screw heads, the cover has probably never been off. I had a big fight getting all the bolts off the lower unit to engine block and I'm not looking forward to getting all these screws off.

In your experience, is it really necessary to remove the exhaust cover? I am only thinking to check for blockages, as I don't want it overheating in this area. If it flows water OK, would this be enough?

Dave
Dublin, Ireland

Welcome to iboats :welcome: good to have you aboard...

Not sure what exhaust cover you're talking about. Could you post some pictures for us to see. That way we will all be on the same page. Also post the year and model numbers so we know exactly which engine you are working on. Johnson made so many variations that there are lots of different models with subtle differences in them...

 

[davedublin]

Re: Johnson 20 hp exhaust cover screws seized

Welcome to iboats :welcome: good to have you aboard...

Not sure what exhaust cover you're talking about. Could you post some pictures for us to see. That way we will all be on the same page. Also post the year and model numbers so we know exactly which engine you are working on. Johnson made so many variations that there are lots of different models with subtle differences in them...[/QUOTE]

Thanks!
I have included a photo. This is a block from a spare engine. I plan to transfer the crankshaft from my engine to this block. I have examined both blocks carefully, I have fitted the crank from my engine and I cannot see any differences that would prevent me from doing this transfer - but I remain to be corrected about this.

I must also confess I didn't look at the core plug until I took the photo and discovered it is an Evinrude, but I think the engines are essentially the same, and seem to share the same part numbers in the parts books.

Where should I find the serial number - on the core plug? Or stamped on the block somewhere?

Dave

 

[gm280]

Re: Johnson 20 hp exhaust cover screws seized

Okay now that I see your problem there are a few things you can try. An easy way to remove those stubborn screws is with a drill press if you have one...even a small bench top size will do. First soak those screws with a good penetrating oil and maybe some heat as well. Chuck up a standard slot screw driver bit that fits those screws really well and the set the block on the drill press base and lower the chucked up screw driver bit on to one of those screw slots. Then take your hand and hand-turn the chuck counter clockwise. Make sure the engine block is stationary and won't move. The screw will have to break loose or break off. And either one is really okay too... If you do have any that break off, you simple drill them out and re-tap using the correct tap for those threads... But taking the unit a part will allow you to see if there is anything clogged up in there and you can de-carbon the area too...

 

[kfa4303]

Re: Johnson 20 hp exhaust cover screws seized

HI Dave. Welcome to iboats. I'm having the exact same issue right now with my '66 20hp Johnson. I'm afraid there's no real trick to getting them out aside from patience, penetrating oil and/or heat. I think they realized the err of their ways using screws as many of the later models used hex head bolts which make for easier removal. Good luck with the surgery. Here are some links that may be helpful.

Vintage Evinrude Johnson Outboard Parts & Diagrams - Catalog 381415 (This is the parts catalog for my '66, but should work for yours as well. If you can post the model number we can pin do they exact year.

Maintaining Johnson E & FD Serie

 

[boobie]

Re: Johnson 20 hp exhaust cover screws seized

An impact type screwdriver may also help you out. For a good penatrating oil, mix up some ATF and Acetone 50:50. You can use propane for heat but Mapp gas is even better.

 

[davedublin]

Re: Johnson 20 hp exhaust cover screws seized

Okay now that I see your problem there are a few things you can try. An easy way to remove those stubborn screws is with a drill press if you have one...even a small bench top size will do. First soak those screws with a good penetrating oil and maybe some heat as well. Chuck up a standard slot screw driver bit that fits those screws really well and the set the block on the drill press base and lower the chucked up screw driver bit on to one of those screw slots. Then take your hand and hand-turn the chuck counter clockwise. Make sure the engine block is stationary and won't move. The screw will have to break loose or break off. And either one is really okay too... If you do have any that break off, you simple drill them out and re-tap using the correct tap for those threads... But taking the unit a part will allow you to see if there is anything clogged up in there and you can de-carbon the area too...

Now that's a method I hadn't thought of - using a slotted screw bit in the chuck. I do have a drill press and I'm going to try your method because it could well get a few of the screws out and save me having to drill them out of the block. It will take a bit of time to make up a platform to which I can mount the block to the drill table, and I will give it a few days with penetrating oil first. Thanks for the tip and I will post my results here in due course!

 

[davedublin]

Re: Johnson 20 hp exhaust cover screws seized

HI Dave. Welcome to iboats. I'm having the exact same issue right now with my '66 20hp Johnson. I'm afraid there's no real trick to getting them out aside from patience, penetrating oil and/or heat. I think they realized the err of their ways using screws as many of the later models used hex head bolts which make for easier removal. Good luck with the surgery. Here are some links that may be helpful.

http://www.marineengine.com/parts/vintage-evinrude-johnson/381415/38141500001.htm]Vintage Evinrude Johnson Outboard Parts & Diagrams - Catalog 381415[/url] (This is the parts catalog for my '66, but should work for yours as well. If you can post the model number we can pin do they exact year.

Maintaining Johnson E & FD Serie

Rear Admiral - Thanks for the links - very good information!

Where is the model number on your '66? I need to find it on mine and I can only see a long number on the core plug on the block. Is that it?

Boobie - I will try your mix for the penetrating oil. Currently don't have an impact driver but could borrow one and it's another weapon in the armoury, thanks.

So I've got some work ahead of me, but it's worth it. They are great old engines.

 

[kfa4303]

Re: Johnson 20 hp exhaust cover screws seized

The model number should be on a small metal tag riveted on the transom clamp. I believe it's on the right side. The FD models are pretty easy to date. My '66 is an FD-20, a '65 would be an FD-19, '64 an FD-18 and so on. Thankfully, virtually all of the parts are identical to the 18hp which were made for years by both Johnson and Evinrude so the exact year doesn't matter much until you get to the mid 70s when they switched to electronic ignitions. Good luck with getting the bolts free. Replacing the gaskets will only take 5min., but getting the bolts out should be "fun".

 

[davedublin]

Re: Johnson 20 hp exhaust cover screws seized

Thought I would update you guys with progress so far.

I tried shifting the screws with an impact driver bit in the drill chuck but ended up breaking the bit! So I decided to drill the heads off. Necessity is the mother of invention, so I had to come up with a method of getting the heads off that would also not damage the casting by drilling off centre, especially with the bolts that are deeply recessed into the casting. I mounted the block on the drill table on a stout piece of wood and drilled the centres using a guide that was a tap fit over the screw heads and which also centred a 5mm drill bit. This gave me the beginning of a hole in the centre of the screw head.

I found that the heads were a bit tough on ordinary drill bits so I then used a carbide 8mm drill (i.e wider than the 1/4" thread) with which I was able to drill right through the heads on centre. Once the screw heads were off, I was able to tap carefully around the edge of the cover after heating it. It finally gave up after a bit of a fight and I was able to save the cover.

The photos show the block after the outer cover came off, the inside of the outer cover and beside it the drill guide and old screw heads, and the block with the stumps of the securing bolts soaking in penetrating oil. I want to avoid the bolts shearing off flush with the casing when trying to extract them, so I will soak them for as long as it takes, then heat the casting and carefully work out the stumps with a vice grips. There is no guarantee that this will work and I may have to do some more driliing and helicoiling. "Fun"!!

I will let you know how I get on with extracting the bolts from the block.

Dave

 

[kfa4303]

Re: Johnson 20 hp exhaust cover screws seized

Glad you're making prgoress Dave. Steady as she goes. Feel free to do mine next

 

[davedublin]

Re: Johnson 20 hp exhaust cover screws seized

Update and Serial number

Success! I finally got the exhaust cover bolts out of the block (see first pic). I heated the block with a blowlamp and worked them out slowly with a vice grip. I found it helped to tighten them initially just a tiny bit and then unscrew them. They were very well seized in the alloy. All the threads in the block have been saved, so no drilling out or helicoiling necessary. Thanks again for your advice and encouragement on this.

My friend who gave me this block read me the numbers and text on his transom clamp. Is this enough for you to get a positive ID?

18502S 0448507
Evinrude Motors Canada
Patented in Canada.... 1957 1956 1960 1962

I have encountered another slight problem. I am using the 2 ring pistons from my motor, which is a later model Johnson, and I cannot ID it because the transom clamp tag is gone. From looking at the parts books for the late 60s 20 hp motors, I am guessing it is a '67 or '68. The two piston rings are the same and measure 0.065" in thickness. A friend ordered piston rings for me but these include one 'dished' ring (second pic) which definitely will not fit. I will have to send them back. Just curious, do you know when these dished rings were introduced?

One other question: the con rod and cap each have a 'pip' on the casting (third pic). Am I right that these pips should be on the same side, top and bottom, if the rod is assembled correctly? I marked them before I took them off but the marks are indistinct now and I would like to be sure.

Dave