Water Passages Clogged in Salt Water Outboards

[Klink]

Within the last year have bought some used boats and engines down here in Florida and have concluded that it is normal to find the cooling water passages in the heads clogged really bad. A 1990 Johnson 115hp, a 1991 Johnson 6hp, and now a 1993 Johnson 25hp, all the same, they were overheating in the test tank or flusher, tested with two different infrared guns. I opened them up and it was clear to see why they were overheating, the passages were totally clogged. An engine can pee great with the heads totally clogged, as the pee outlet is before the water gets to the heads.

I've also gotten five (yes five) little Force outboards 5hp within the last 6 month, they were practically unused, yet three were totally clogged. Keeping score? Eight engines, and only two were not totally clogged. That's Florida, where people can go out in saltwater year round.

In all the engines I had to remove the heads (and deal with stuck bolts, broken bolts!)and physically clean them with screwdrivers, SS wool, sandpaper, wire brushes, drill bits, whatever, till all the obstructions are removed. Then install new headgaskets, cover gaskets, diffusers ect. Today I had to do it on the 25hp Johnson that I just bought 2 weeks ago. Not a fun job. Used Florida outboards? Test them in a tub with a infrared thermometer gun before you buy! I will from now on.

 

[Klink]

Like I said, I just had to take apart the head on my just bought 1993 25hp Johnson because it was overheating upon my first test in the tank. I test them with a digital infrared thermometer. The engine temperature kept going up and up till I shut it off at 178 degrees. I opened up the head (not an easy quick job if it was used in saltwater as the bolts all lock up and breakoff!) and found it all clogged up. Moreover, the thermostat was locked up and totally clogged, not a drop of water was going out the exhaust everything was just recirculating, hence the temperature kept going up and up.

I discovered that to get to the thermostat on this engine, you have to remove the entire cylinder head cover plate, that's 14 bolts by itself, let alone that you have to remove the coils, power pack, spark plugs and wires and then some, just to get to the plate with it's 14 bolts! CRAZY!!!!

No way I'm going to put in a normal thermostat that may lock up tomorrow if it's defective. This is the ideal situation to use the hatless thermostat, which will never fail! I'm not going through this again. Hopefully my flushing the engine with fresh water will give me some years before I have to go back and clean the heads again, maybe 20 years, as I don't think the prior owners ever did it.

In warm climates many people use a thermostat with the hat cut off (the part that open and closes). Doing this still restricts the water flow to what it would be with the thermostat wide open. Any old stuck thermostat can be re-used by just cleaning it and cutting off the hat. There is no need to remove the thermostat altogether, don't even think of removing the thermostat and go without out it altogether that is not the best idea. Besides why would you want to do it, the "hatless method I described cost nothing.

 

[Klink]

Remove the hat, the part that opens and closes on the top.

 

[Chris1956]

Gee, that is unusual. I have run motors for 20 years in saltwater. None has ever clogged. I do flush them with freshwater before off-season storage, and occasionally during the season.