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Just bought a 6HP 6R79E

S

SMOKEU

Member
Hi everyone,

I'm new to boating and just bought my first boat, a Fyran 10' aluminum boat with a Johnson 6HP 6R79E. Now I'm completely new to outboard maintenance, and I want to make sure the engine is serviced properly before I hit the water. The engine hadn't been started in about 5 years until today. At first there was no spark, so we cleaned out some minor rust on the electrical leads and then we had spark. The engine seems to run nice and quiet, and it's easy to start now.

However, the engine isn't pumping water that well. Should I buy a new impeller, or a whole cooling system kit which includes the impeller? I'm guessing I should also do a gearbox oil change. What oil do I use? I'm planning on replacing the spark plugs as well. It is tempting to send it to a boat shop, but they all charge like a wounded bull around here and parts are horrifically expensive here in New Zealand so I'd like to know what parts I should import. It's an old engine that I don't want to spend a lot of money on, but I do want it to be reliable. So where do I start?
 
Thanks for your help with that!

In the mean time while I'm waiting for those parts to arrive, I'd like to take it out this weekend. I've bought a new impeller, and I'll replace the gearbox oil and spark plugs. What plugs should I get? Are NGK ones OK? They're the most common ones here. I'm thinking of using manual car gearbox oil.

So if I change the gearbox oil, spark plugs, and impeller as well as greasing all moving parts under the engine cover, will that be enough? Anything else quick and easy to do while I'm at it? Anything to look out for? Is there a free workshop manual available for it?
 
Hell you need to use 80w90 marine gear lube for the lower unit. NGKs should work fine as long as they are a direct replacement I prefer champions myself for omc motors.
 
So I ended up sending the engine to an outboard mechanic. He replaced the impeller and gear oil for me as well as giving the engine a general check. He said the water jackets inside the engine are quite blocked with salt so the engine is going to run quite hot.

I took it out last weekend for the first time and it went really well, but the water coming out of the engine was very hot, almost too hot to touch. The mechanic suggested I even remove the thermostat completely as that might make it run a bit cooler.

So my questions are:
1. Is there any easy way to clean out the inside of the engine water jackets without taking the engine apart? I'm thinking of running it in a container of Salt Away or other such product.
2. Should I remove the thermostat?
 
Get a jug of saltaway and fill up a barrel of water and add a gallon of saltaway and let the engine run until the water in the barrel gets warm. Do not remove the thermostat and monitor the head temp. You should be able to hold your hand there for a slow count to six.
 
kimcrwbr1 said:
Get a jug of saltaway and fill up a barrel of water and add a gallon of saltaway and let the engine run until the water in the barrel gets warm. Do not remove the thermostat and monitor the head temp. You should be able to hold your hand there for a slow count to six.
Click to expand...

Thanks - I might try that tomorrow. I've also read that some people recommend using a mix of white vinegar and water, do you think this will help? What ratio of vinegar:water should I use?
 
I the saltaway dont work nothing will. You will need to take it apart and clean the circuits good and install new gaskets. Pull the thermostat just to inspect the head and start it for a minute and see if you get water gushing out the hole. You can test the thermostat by putting a string in the valve, then hold it in the center of a pan of water with a meat thermometer right next to it. It should fall off the string around 140 degrees.
 
Fresh water or salt water you should allways flush the motor when you get home in a barrel with tap water in it. Put the water level half way up the leg and run it until the thermostat opens and then disconnect the fuel line and let it run out of fuel. I use a garbage can with a small hole in the bottom. By the time your done cleaning the boat the barrel is empty.
 
Today I put it in a bucket of fresh water with vinegar . I used roughly 1 part of vinegar with 3 parts of water. I idled the engine for a few minutes to warm it up, then revved it to half to 2/3 throttle for about 10 minutes until the water outlet became very hot, too hot to touch. I shut it off to let it cool down and repeated the process several times over the course of 2 hours.

Now the engine seems to pump water much better at idle than it did before. There's a good, strong stream of water at idle whereas before there was a weak, intermittent flow. So the vinegar did something.

I took the boat out today with this outboard, and after about a minute of full throttle I start to feel it lose a little bit of power, but nothing drastic. If I then stop and feel the water outlet immediately, it's very hot. I can only touch the water for 1-2 seconds before it starts burning my hand. If I run it at 1/3 throttle, or even just over idle, the water outlet is hot but I can still comfortably touch it. The sea temperature is around 17.2°C. Is it still worth using Salt Away or a stronger vinegar solution and trying again?
 
No one here told you vinegar would do any good. if you cannot hold your hand on the head for a slow count to six immediately stop the motor you are overheating it. Evidently you didnt pull the thermostat either?
 
kimcrwbr1 said:
No one here told you vinegar would do any good. if you cannot hold your hand on the head for a slow count to six immediately stop the motor you are overheating it. Evidently you didnt pull the thermostat either?
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I've read about the vinegar trick from a few other forums. I'll pull the thermostat next and take a look.
 
That motor is approaching 40 years old, and salt water use yet. I have special respect for you Australians. You manage to keep these things running forever. But if the cooling system is plugged up, it is plugged up till you get in there and physically clean it out. Even then, the factory (red) protective coating is probably gone. If it still remains, do not remove it.

There are TWO water flow paths through that powerhead. Only one path goes through the thermostat. What this means is that water can be flowing through one path but not the other, resulting in overheating.

You probably will bust off a bunch of bolts opening it up. Good luck.
 
kimcrwbr1 said:
http://www.ebay.com/itm/143-Thermos...ash=item41a3afefc5:g:RHoAAOSwuYVWpjk9&vxp=mtr
Can you depress the spring to open the valve? Like I said stick a string in the valve and hang it in a pan of water hold the meat thermometer next to it and see what temp it falls off the string.
Click to expand...

The thermostat seems stuck. Time for a new one.

fdrgator said:
That motor is approaching 40 years old, and salt water use yet. I have special respect for you Australians. You manage to keep these things running forever. But if the cooling system is plugged up, it is plugged up till you get in there and physically clean it out. Even then, the factory (red) protective coating is probably gone. If it still remains, do not remove it.

There are TWO water flow paths through that powerhead. Only one path goes through the thermostat. What this means is that water can be flowing through one path but not the other, resulting in overheating.

You probably will bust off a bunch of bolts opening it up. Good luck.
Click to expand...

Think further south than that mate, New Zealand!

I've got about 2/3 of a litre of Salt Away, should I run the engine in a bucket with 20 litres of water with the Salt Away? I was thinking of running it without the thermostat for 10 minutes at fast idle, leave it for 30 minutes, run it for another 10 minutes, leave it for 30 minutes..... and repeat over the course of 6 hours. Then after that I'll flush with plenty of cold water. Sound like a good idea?

Should I also get some wire and shove it down the water jackets to try and loosen the salt? I'm hesitant to open it up in case I snap bolts off.
 
Another idea was to block up the water inlet and tell tale outlet and main water outlet, then put some very concentrated Salt Away down the thermostat hole and leave it for a day before flushing it out. Anything to improve it.
 
Put the cover back on without the thermostat and run the motor for about ten minutes. If the head stays cool wait for the new thermostat and run it again with the thermostat and saltaway for about 1/2 hour. then drain the barrel and flush it out good with fresh water. The head should get hot enough you want to pull your hand away but dont have to.
 
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