Johnson RDSL-21 mercury Switches

[Tom Alexander]

Lindy 46: Good eyes! Thanks for that. You are right and for subsequent runs I did raise the water level. For this first run I did have a pressure water (Municipal water supply) source feeding into a screwed on plate on the intake to make sure I had water into the supply side of pump. While I don’t think this ‘proves’ a water pump is working sufficiently on its own, for the  first approx 10 minutes of running I did keep the hose pressured up and connected just for my peace of mind. Then I disconnected and the pump has proved since to be working well.

Thanks  Tom Alexander

[Mumbles]

If you haven’t already replaced the original impeller, you best put that chore at the top of your ‘to do’ list even though it is working now. After sitting for many years, it will have taken a set and developed cracks. It’s not a matter of if it fails, but when.

[Tom Alexander]

Mumbles: thanks for the thoughts. I completely rebuilt the gearcase as it was very rough when I turned the prop by hand when I got the boat and engine. I found that the pinion gear shaft bearing surface and it’s bearing was badly corroded probably due to the seal below the impeller failing.  The drive shaft was badly worn at the seal contact point just below the water pump. I tried to fix with a seedy sleeve but the sleeve would not go over the splined end of the shaft and not take the ‘shape’ of the splines, so I located a new/old shaft that was in very good shape. It has a tapered area narrowing toward the top so we will see if it is up to the task. But to the point you made I did replace the impeller and the pump ‘body’ too at time in rebuild. The impeller did not look at all like the one in you photos though. On Diesel engines I have had the pump folks had impellers that could handle a bit of dry running. I think they were blue in color. I could fine nothing like that in the outboard motor pump information I researched. Any info in that regard?  Thanks again. Tom

[Mumbles]

OK, I should have known but just wanted to make sure.

Speaking of diesel,  here’s what I found in my AMARC  diesel outboard. Pretty, ‘eh?

 

 

• This reply was modified 3 years, 2 months ago by Mumbles.
• This reply was modified 3 years, 2 months ago by Mumbles.

[Tom Alexander]

Nasty! But at least all the vanes are still there. Last time I overhauled my heat exchanger I found the revenants of 3 vanes.  Tom

[fleetwin]

Yeah, I would raise the water level in that bucket a bit so the gearcase to extension hsg joint is completely submersed.  I see alot of steam coming out of the exhaust relief, is there any water in the steam spray?  How long was the engine running when you made the video?  Did it appear to be getting hot?   Yes, it is fairly normal for these engines to steam a bit, but it could also be overheating as well.

[fleetwin]

Tom Alexander wrote:

Lindy 46: Good eyes! Thanks for that. You are right and for subsequent runs I did raise the water level. For this first run I did have a pressure water (Municipal water supply) source feeding into a screwed on plate on the intake to make sure I had water into the supply side of pump. While I don’t think this ‘proves’ a water pump is working sufficiently on its own, for the  first approx 10 minutes of running I did keep the hose pressured up and connected just for my peace of mind. Then I disconnected and the pump has proved since to be working well.

Thanks  Tom Alexander

Yes, using that water supply adapter can surely mask a bad water pump.  There is no need to use it when the engine is being run in a bucket.  You go on to say the water pump is working just fine, how did you determine this?

This engine looks to be in beautiful original condition, perhaps someone repainted it.  You do want to be very sure that the cooling system is working properly before using the boat/engine out on the water.  Overheating at high speeds causes damage very quickly.

[Tom Alexander]

Hi: yes there is water coming out that ‘exhaust relief’ port. Enough that it wets my hand to the point of water running off it in seconds. Warm steam(?) too. Right now I am not doing any ‘runs’ longer than about 2-3 minutes and those are not going over a quick excursion into the 2000 rpm realm. Think fast idle more or less. So I think the cooling system is performing normally? That is the reason I said what I did about the water pump working correctly. This could be my wishful thinking of course after the hours spent rebuilding the gear case and associated bits and pieces including the water pump. I will do a much longer run soon when I get my temperature measuring gear in place and let the engine really reach ‘operating’ tempature (150-165?). Right now my time is split between getting this done and getting the engine and prop aligned in a 1953/55 Mercury Ski Tug. It’s an old Gray Marine just back from a rebuilder who shall remain nameless as he did such a sh*;%ty job and charged me moonbeams. That is a Kiwi expression for heaps of money. Life is a balancing act but I would like to be able to get both boats wet this spring. Wish me luck!

[fleetwin]

OK, sounds good as long as water was mixed with the steamy spray, which is normal for these engines.  This engine might have a “hot light” on the dash which connects to the head with a single tan wire along with a knife connector covered in a rubber sleeve.  On the other hand, the 59 models may not have included this feature.  If your engine is equipped with a hot light, you will want to check to make sure it works.  With the key turned to the “on” position, carefully slide the rubber cover back exposing the knife connection.  Now ground the knife connection to a clean ground on the head or perhaps on one of the head bolts, the hot light should illuminate.

[Tom Alexander]

Fleetwin: Thanks for the info but this doesn’t have that hot light feature. Not in the wiring from box at stern or on the dash panel. I will be running the engine with temperature  monitoring gear on the top cylinder head and thermostat early this coming week. Trying to be ultra careful with run time, RPM and external temperatures. I wonder what else there its hiding out there to bite me in the butt!!?? Thanks  Tom Alex

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