Outboard Engine Repair (again)

While we were anchored near Cavtat, Croatia about 7 weeks ago we experienced a very serious that storm hit suddenly. Judy, Zachary, BeBe, Judy and I worked hard and successfully to raise the anchor and motor out to deeper water in winds sometimes gusting over 50kts. Unfortunately, the dinghy painter got tangled with the dinghy propeller as we were maneuvering and the tangle caused us to drag the dinghy backwards out to sea. This backward towing of the dinghy caused the motor to go under water several times for a few seconds.

After the storm, Zachary and I pulled the motor on deck, cleaned and lubricated everything and drained all the sea water out of the engine and carburetor. It is a 2 cycle engine so there is no crankcase oil to change. We connected the gasoline hose and after numerous attempts we were able to restart it. The dinghy engine worked fine for several weeks, then quit. I diagnosed and electrical ignition failure and it was beyond my ability to repair. I assume that the sea water caused this. We motored to Split, Croatia and had a Mercury Outboard shop repair it for about $350. They replaced a number of electrical parts, rebuilt the carburetor, and cleaned everything then returned it in fine condition. I was very pleased.

Make-shift workshop

About 2 weeks later, the sea water pump on the engine, inside the lower unit near the propeller shaft stopped pumping sea water. This is something that I should have asked the Mercury dealer to check, but I failed to ask. It had been about 6 years since I changed the impeller and seals on that pump. 

Oh well, I had the spare parts and early one morning went to work. I was dreading this job because Mercury has cast aluminum housings bolted together with stainless steel bolts. If you know anything about mixing these metals, you know that there is a huge risk of shearing a bolt, stripping the threads in the aluminum case, or both. I took my time, used that last of the penetrating oil I had, and was very lucky...no big problems. When I disassembled the lower unit and pump casing, I found that the pump casing gasket was missing, the impeller was basically OK, and the Woodruff key that secures the impeller to the shaft was missing. My assumption was that the impeller was spinning on the shaft and because of that, not pumping water. What to do? I have no impeller key and no gasket and we are 100 miles from the unlikely possibility of finding parts.

Cutting to the correct length 

Dremel grinding and cutting tool -
Shown with 4mm bolt and Impeller

Grinding the flat side

I decided to make both of the parts. The gasket was easy...just use some silicone RTV from a tube that I have on-board (I have several tubes of varying types). The key was a different story. The key was about 10mm (3/8") long and flat on one side and round on the other. It was about 4mm thick. I found a 4mm stainless steel bolt that was 3 times as long as I needed. I used the Dremel that Trey, my oldest sun, gave me and flattened one side of the bolt. Now the bolt was flat on one side and rounded on the other. The impeller has a hole in the center which allows it to slide onto the shaft and the impeller key was designed to fit in a rounded slot on the side of the "shaft-hole" in the impeller in such a way that the flat side of the key matched up with a flat spot on the shaft. This way, the impeller is locked to the shaft and not allowed to spin. 

Finished new key

Key on the Impeller

Once I had the right shape, I used the cutting tool on the Dremel to cut my new key to the correct length...Done!

Flat spot on the shaft for the key

Impeller and Key in Place

By 2:00PM, I had the engine reassembled and mounted back on the dinghy. Started it up to test the pump, and it did not pump a drop of water. It was not working. 

OK, something is wrong...I take it off the dinghy, up to the makeshift workshop on the boat...and disassemble again.

I suspected that something was blocking the copper tube that carries the sea water from the pump up to the engine. I took out my dive tank and a hose and nozzle that I recently purchased to blow things out. I had used this nozzle a few months before to blow "trash" (reconstituted corn from Eurogas) out of the dinghy engine carburetor. OK, now I am ready.

So I go through all of the steps to remove the lower unit...the same thing that I did earlier. This time is a lot quicker because those stainless steel bolts come right out of that cast aluminum housing. I had used anti-seizing grease on the bolts. Thanks, Dennis!

In no time, I am using my nozzle to blow air through the cooling system. I blow from the bottom...no joy. I blow from the top, no joy. I decide to try pumping water from the top and the bottom...no joy.

Removing the mid-unit -
piece between the engine and the lower unit

I cannot seem to find the clog, except that I now know it is somewhere in the copper pipe, or where the copper pipe connects to the engine base. It is now time to remove the mid-unit which is another cast aluminum case with stainless steel bolts. I get it done with no problems...it was truly my day in at least one area. I get the aluminium mid-unit case off and now have access to the bottom plate of the cooling and exhaust plate which is secured with more stainless steel bolts...again I am successful with these, having to use my portable torch on one troublesome bolt. 

Copper tube through mid-unit

Looking for the elusive clog

It appears at this point that the copper pipe is clogged. I attempt to run a solid stainless wire through the copper pipe...no joy. I happen to have a piece of twisted stainless steel rigging wire that will fit inside the copper tube. I cut it to the length I need, insert one end into the chock on my electric drill and the other end, I slightly flay the end so that it will act as a roto-router. Into the copper pipe and on with the inverter to power the drill...I am getting all sorts of trash out...more like gunk...no big pieces. I take the nozzle and blow out the remainder...finally JOY!

I reassemble the engine...it works and pumps lots of sea water! A wonderful shower and a half hour later Judy and I take the dinghy to another boat for a really good beer. Thanks, Dennis and Virginia on Libertad for the beer!!!

And a super thanks to Judy for helping me with this difficult project.