adding oil to gas vs. auto injection

jstaz

Seaman
Joined
Oct 3, 2010
Messages
64
I have a 1994 Tohatsu 60 HP that has and oil tank and it does the whole auto injection thing. However, I have read and heard and been told that many fellas don't trust that system because if it fails you burn up the motor. They state to mix your gas.

Should I do this for insurance?
Do I need to disconnect the oil injector system or can I mix and keep that system operational?
Whether I keep it hooked up or only mix the gas... What ratio should I mix? 50:1? 25:1?

I am new at all this so any help and comments would be helpful. Thanks in advance y'all.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,035
Re: adding oil to gas vs. auto injection

Whereas it is true that if the oil injection system fails, the motor burns up, it is also true that if you forget to add the oil to the gas, the motor burns up just the same. The question is who is more reliable, you or a mechanical system?

I would start asking the Tohatsu gurus how reliable is the oil injection system and weigh their answers agains your personal reliability.
 

Skiwi

Petty Officer 3rd Class
Joined
Oct 9, 2010
Messages
84
Re: adding oil to gas vs. auto injection

Personally I prefer to premix, then I know if the motor is running it's getting oil.

However as Chris points out, it still relies on someone remembering to mix in the 1st place!

I have a simple routine, tote tank(s) out of boat, full up, then the tank does not go anywhere near the boat until it has oil added, once I've added oil, straight back into boat.

So I know if it's not in the boat it hasn't got oil, and if it is, it has :)

...and I'll wager more motors have be burned from human failure than from mechanical ;)
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,035
Re: adding oil to gas vs. auto injection

The oil injection on my '98 Johnny 150HPV6 has been proven to be very reliable, and has low oil and no oil sensors. It is real convenient to use, versus mixing up 25gal of fuel each time I want to go fishing. The mix is always fresh as well.
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: adding oil to gas vs. auto injection

Disconnect the injection, disconnect the warning sensors. Doesn't make sense to me. We've rebuilt many more motors because someone forgot to add oil / didn't add enough than because of a TRUE injection system failure.

Oil injection, don't leave the dock without it.
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: adding oil to gas vs. auto injection

How often does an oil pump on an automobile fail? Do we worry about that destroying our engine?

I think that auto mix systems failing are an urban legend. Don't listen to the low oil warning or run without oil and you will ruin the engine, but that's not the pump's fault.
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: adding oil to gas vs. auto injection

How often does an oil pump on an automobile fail? Do we worry about that destroying our engine?

I think that auto mix systems failing are an urban legend. Don't listen to the low oil warning or run without oil and you will ruin the engine, but that's not the pump's fault.

Exactly!! Well put Frank!
 

j_martin

Admiral
Joined
Sep 22, 2006
Messages
7,474
Re: adding oil to gas vs. auto injection

Well, there are times when it's prudent to block off the oil system. On a V6 merc, the drive gear is nylon. If the engine is grossly overheated, that nylon gear is compromised. If you don't wreck the engine, it's a good idea to block off the oil pump at that time and pre-mix. You have to pull the powerhead and split it to replace that drive gear. Save the injection parts, as you will be overhauling it soon anyway, and that's a good time to refresh the nylon gear.

The other time is if you mod the engine to turn extreme RPMS consistently. The Merc oil pump is not reliable above about 6500 rpm's.

I once saw an old man cry on the landing. He had forgotten to add oil to the gas and fried a vintage (green) mercury 5 horse.

Pay attention. Look into it if the power on self test (POST) tones are not heard when you turn on the key, and if the alarm goes off when running.
 

riptide09

Petty Officer 1st Class
Joined
Sep 11, 2009
Messages
297
Re: adding oil to gas vs. auto injection

I have never had a problem on my '03 Johnson. The oil injection system works as advertised and to me it is way more convenient than adding oil to the gas, especially when i don't know exactly how much gas it will take to fill the tank.

If the oil injection systems were unreliable they would not continue to make them. Maybe when they first came out there were issues but that was 20+ something years ago.
 

tx1961whaler

Vice Admiral
Joined
May 31, 2008
Messages
5,197
Re: adding oil to gas vs. auto injection

Have a buddy that does both. Pre-mixes at a 100:1 and still uses the oil injection.
 

bassman284

Commander
Joined
Jun 24, 2006
Messages
2,839
Re: adding oil to gas vs. auto injection

Have a buddy that does both. Pre-mixes at a 100:1 and still uses the oil injection.

Kind of like folks who ues synthetic oil in their car or truck and change it every 3000 miles. JUST TO BE SAFE.

PEACE...of mind.
 

109jb

Lieutenant Commander
Joined
Jul 15, 2008
Messages
1,590
Re: adding oil to gas vs. auto injection

How often does an oil pump on an automobile fail? Do we worry about that destroying our engine?

I think that auto mix systems failing are an urban legend. Don't listen to the low oil warning or run without oil and you will ruin the engine, but that's not the pump's fault.

This isn't even a good comparison. In our 4-stroke cars we have absolutely no choice because the lubrication system is not even connected to the fuel system. The oil and the fuel never mix. On a 2 stroke, the oil and gas mix, it is just a matter of whether a person or a piece of machinery is doing the mixing.

Do 2-stroke oil injection systems fail. You bet they do, but they are for the most part very reliable. I ride snowmobiles and although I have never had an oil system failure I have a friend that had one fail and lost the engine.

As was stated before it depends on the system. My father had a 60 hp Johnson with the VRO system. Not known for its stellar reliability. We disconnected it and ran premix in that engine. I now have a 115 Mariner and relatives have had many Mercury's and they have a reliable proven oil injection system. So, the system on my Mariner is still pumping oil into the engine.

Can someone forget to premix?? Yes, I suppose, but I've premixed for 20+ years before the boat I have now and I never forgot because it was a given that you add oil every time you fill the gas tank.

Can someone forget to add oil to the oil injection tank?? Yes. I have done this because the big oil tank lasts for many tanks of fuel. Has it ever gotten low enough to be a problem?? No, but if someone were to get complacent enough with checking the level then it could be a problem. I will tell you that when I got my boat the warning buzzer did not work. The buzzer itself was bad and all the sensors in the world don't mean nothing unless the sensor has a way to notify you.

Like I said, to me it depends on the system whether I would unhook it. Some I would unhook, some I wouldn't.
 

jstaz

Seaman
Joined
Oct 3, 2010
Messages
64
Re: adding oil to gas vs. auto injection

Thank you all for your input and help. I have learned a lot.

Does any one know the reliability of oil injection systems on Tohatsu motors?
 

bassman284

Commander
Joined
Jun 24, 2006
Messages
2,839
Re: adding oil to gas vs. auto injection

Try posting your question on the Tohatsu board. Tohatsu Guru hangs out there and pretty much knows what there is to know about Tohatsu.
 
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