1974 6R74C engine water leak.

[mikster01]

Got a 6 hp Johnson and a 12 foot Jon boat given to me. Was told the engine did not run. Read like a fiend for 2 days. Checked out some stuff. Found the Low idle setting was so far in you could not turn it. Used Pliers to turn it ( Knob not strong enough). Got a new gas tank and lines..... Choked it pulled it three times and it started up. Ran for about 2 hrs through all revs of the throttle. Would idle for ever after making an adjustment to the low idle screw... Purrs like a kitten. Gears change fine, and went to full power in gear in the tank. Think its a winner.

Saw one issue. On the top back of the block, there is a little water leaking from the plate that covers the thermostat. Is that a big issue. Seems to stop after it heated up, but if I wipped it off, it would be back inabout 10 mins. Not a lot of water, just a little pool (quater size) over about 10 mins. or so.

Question is, is it as simple as removing the cover plate, and replacing the gasket??? Need to put any RTV or anything???? Any Idea for the Torque of the 3 bolts?

 

[jrs_diesel]

Re: 1974 6R74C engine water leak.

Just checked the service manual for my 72 6 HP. There is a gasket under the thermostat plate, part number 311145. No RTV needed or required, although you could put some Evinrude Gasket Sealer on it. I believe the bolts are #12 screws, so the torque on them is 35-40 inch pounds. If they are 1/4-20 bolts, then the torque is 60-80 inch pounds.

 

[mikster01]

Re: 1974 6R74C engine water leak.

Thank you jrs_diesel...

Also an alternate/replacement for 0311145 gasket is 18-0679. Just over 2 bucks.. not bad.

 

[dazk14]

Re: 1974 6R74C engine water leak.

Probably biggest risk is bolts breaking. Of course they may come out like butter.

Give the bolt heads a tap with a hammer to shock them a bit. Their are many more ways to loosen them WITHOUT breaking.

Inspect thermostat.

 

[mikster01]

Re: 1974 6R74C engine water leak.

Thanks for the warning. I don't believe they are stuck as I applied a wee bit of tightening to them to see if the leak would stop... And I mean a wee bit, but they did turn.

What am I inspecting for with the thermostat??? Should I take it out and boil it to see the operation? or am I just checking for corrsion... And I guess for that matter that it is even there... Down here in LA and TX they tend to remove them as it is always hot..LOL

 

[jrs_diesel]

Re: 1974 6R74C engine water leak.

Yep, basically looking for corrosion, thermostat gasket condition, and anything abnormal. You can put the thermostat in a pot of water, just use a thermometer to verify that it opens up around 140?.

I don't think anyone here would tell you to run an engine without a thermostat, as that would cause the engine to run too cold, burn more fuel, and foul the spark plugs faster.

 

[jay_merrill]

Re: 1974 6R74C engine water leak.

Yep, basically looking for corrosion, thermostat gasket condition, and anything abnormal. You can put the thermostat in a pot of water, just use a thermometer to verify that it opens up around 140?.

I don't think anyone here would tell you to run an engine without a thermostat, as that would cause the engine to run too cold, burn more fuel, and foul the spark plugs faster.

I've owned several Johnson 6hp motors. Whether or not you need a t-stat depends on the water temp where you operate it. If the water is warm enough, it doesn't make any difference. I ran a pair on them on a boat for several years with no t-stat and had no problems. No fouling, no abnormal carbon buildup, etc.

Its all about the cooling water reaching an appropriate temp.

 

[mikster01]

Re: 1974 6R74C engine water leak.

Thanks for all the help.. And Jay, you are from the WhoDat Nation... You do understand why someone would remove the t-stat.
I understand the need for one, but the thought for many here is that our surface water temps are in the high 70s to low 90s most of the boating season. Air temps are even higher. The motor WILL get to temp no problem, and would much rather not have a t-stat that could fail...

Thanks again... Got the gasket on order and a few more items as well... I will let you know how it goes.

 

[superflydudebike]

Re: 1974 6R74C engine water leak.

How thick is this gasket supposed to be? I need to replace my 1972 6 HP one and I have various gasket materials at home so I plan on making one for it. Original gasket was so bad that it is hard to tell how thick it should be. I looked for specs online with no luck.