Oil pressure light on Nissan/Tohatsu 6hp

[dwiedwald]

My 2007 Tohatsu 6 hp has a red oil pressure indicator light. It came on a few weeks ago and I changed the oil right away. The oil was very dirty. It went a way but yesterday it came on when I increased the throttle to a higher RPM. The light came on over about 75% speed but stayed off below that. Do you have any ideas?

I bought it used about 3 months ago.

 

[Wee Hooker]

Re: Oil pressure light on Nissan/Tohatsu 6hp

Did you cahnge the filter too?

 

[pvanv]

Re: Oil pressure light on Nissan/Tohatsu 6hp

The 4/5/6 does not have an external filter. You may have a sludge problem, or other issue. Change the oil again, and see if more crud gets flushed out with the oil. You may either have low oil pressure, or a faulty lamp circuit. Sometimes the low oil pressure switch can fail. You can check the actual oil pressure with a gauge. A Factory service manual will show the location of the switch. That's where you can connect a mechanical gauge to test pressure.

 

[DrLove]

Re: Oil pressure light on Nissan/Tohatsu 6hp

I've got the same problem on my 2009 6HP Tohatsu Sail Pro. It has less than 5 hours on it, so I don't think it's a dirty oil problem. Like you, lower RPMs seem to not have the problem, but around 40% or higher RPMs the red light starts to flicker. It's not constant not consistent, but does seem to happen more when at higher RPMs.

I've had it back to my dealer twice. He has had a hard time recreating the problem in his shop.

The first time he attached an oil pressure tool to it and it showed that it had oil pressure at all RPM ranges. Since he could not recreate the problem, he gave it back to me and said that maybe something had been clogged and now was not clogged any more. As soon as I got it home, I put it on a saw horse with 5 gallon bucket and immediately recreated the problem.

So, I took it back. His test well is metal, so we speculated that maybe he was grounded while I was not. So, he put wood around his well and still could not recreate it. But, he replaced an electrical part on it stating (from my poor memory) something about an electrical loop interference that might be the cause. He worked with a guy in Texas who is a Tohatsu mechanic representative. When I went back to pick it up I brought my saw horse and 5 gallon bucket and the light did not show up through about 10 minutes of testing.

Then, two days later I put it on the boat, headed "out to sea" and it started flickering again.

My dealer is 1.5 hours drive round trip. So far I have 7.5 hours of driving time, plus two times swapping my old reliable 1986 Honda 7.5 with the Tohatsu at the dock. So, it's a real pain trying to get this resolved. Yesterday I asked for another motor due to the fact that I am so far from the dealership. I'm waiting to see what happens with that request.

If I find out anything else I will post back to this thread.

 

[mmccoy555]

Re: Oil pressure light on Nissan/Tohatsu 6hp

it could be the light or sensor itself going bad. I've seen that happen a few times.

 

[pvanv]

Re: Oil pressure light on Nissan/Tohatsu 6hp

One of two things is true: Either you are detecting actual low pressure, or you are getting a false indicator.

If the oil pressure is good (as shown on a mechanical "shop" pressure gauge), then the indicator circuit has a (possibly intermittent) fault. The likely culprit is the oil pressure sender. Senders can fail thermally (fail when hot), so that's a real possibility.

Confirm that you have the correct oil level. If the oil is overfilled, even a little, it can foam up, especially at higher RPMs, causing air bubbles in the oil system, resulting in actual low pressure. Not uncommon.

Intermittent faults can be very elusive, and quite difficult to pinpoint. Patience is required, and sometimes a few hairs are pulled out of the mechanic's head while trying to isolate the issue. That said, the oil light circuit is not particularly complex: The power is generated by the magneto and CD box (same as generating the spark), and the sender is a ground-out switch, that controls whether the LED comes on or not. If the power supply for the circuit were inoperative, the LED would not come on at all. So an LED that gives a false low-pressure indicator is likely either a wire shorted to ground, or a defective sender.

BTW, be careful using a small bucket for a water supply, as you can suck air into the motor, and burn up the impeller.

 

[DrLove]

Re: Oil pressure light on Nissan/Tohatsu 6hp

I just talked with my dealer/mechanic and he gave me the specifics on what he's done. He has replaced the "Ignitor" as well as the "Sender". Neither of them fixed the problem.

Tohatsu wants him to try a few more things. First, his oil pressure gauge was a 150 PSI one. They want him to use a lower PSI one. Their thinking is that the fluctuation is so small that it won't show up on the higher PSI one.

Also, the mechanic thinks there might be some "crud" in the release valve that keeps the engine from getting too much pressure built up. So he wants to take some steps along trying to flush out the system.

In any event, I will be taking the engine back to him as Tohatsu doesn't want to replace the engine but instead have it fixed. I really don't blame them at this point. I guess I'll just have to be inconvenienced for a little longer. I'll post back if we get it fixed. It might take several weeks to get to it.

Hey pvanv, thanks for your input on the bucket. I never thought about that. I'll find or build a larger well.

 

[goncken]

Re: Oil pressure light on Nissan/Tohatsu 6hp

Similar problems with 6hp. Oil light flashes intermittently at low speed. Been to Tohatsu mechanic three times. Finds no problem. Suggests maybe faulty light and just ignore. Last time out, running at about 3/4 throttle, light begins to flash, engine dies and will not restart. Towed in. Two weeks later go out to get motor off boat, try to start. It starts first pull and idles smoothly in slip for over an hour. Bought motor used for $700, have spent $400 having it worked on for this problem, could have bought new motor for what I have in this one. Frustration, no answers, need suggestions on what to do next.

 

[Socal Pat]

Re: Oil pressure light on Nissan/Tohatsu 6hp

Oh great! I just bought a barely used '09 Nissan 6hp. I hope I don't get to join the club.

 

[pvanv]

Re: Oil pressure light on Nissan/Tohatsu 6hp

We have sold dozens of 4/5/6 4-strokes, and have not had one in-warranty oil pressure problem. These beaters are almost indestructible. Troubleshooting the actual issue (rather than guessing) will be the way to go. Either the oil pressure is indeed low, or you are getting a false indicator. A mechanical shop gauge will remove all doubt, since it will prove the exact oil pressure.

Once you determine whether you actually have correct oil pressure or not, you will know what issue to address. If the pressure is indeed low, then mechanical repairs are called for. If the pressure is correct, then you are getting a false indication, and electrical service is called for. Pretty straightforward.

What did the mechanic do, aside from not fixing the problem, suggesting you ignore the warning light, and yet charging you? What is the actual oil pressure, as shown on a shop pressure gauge? Was the dealer able to reproduce the problem in the shop? See if the mechanic will stand by his work, and complete repairs.

Similar problems with 6hp. Oil light flashes intermittently at low speed. Been to Tohatsu mechanic three times. Finds no problem. Suggests maybe faulty light and just ignore. Last time out, running at about 3/4 throttle, light begins to flash, engine dies and will not restart. Towed in. Two weeks later go out to get motor off boat, try to start. It starts first pull and idles smoothly in slip for over an hour. Bought motor used for $700, have spent $400 having it worked on for this problem, could have bought new motor for what I have in this one. Frustration, no answers, need suggestions on what to do next.

 

[DrLove]

Re: Oil pressure light on Nissan/Tohatsu 6hp

Well, it took until just before Memorial Day 2010 to finally get my motor fixed - but it is fixed.

I won't go into all the details of what my mechanic replaced, but he did a lot of troubleshooting and parts replacement. It turned out to be a small metal "burr" somewhere in the oil passage that caused the fluctuation. I'm sure this is a rare occurrence.

I should note that my mechanic (Chuck Holm in Mayo, MD) offered to give me a loaner until this was resolved, which I declined but appreciated. I used my old Honda until it was fixed so I didn't miss any sailing time. I appreciate the professionalism that Chuck displayed during this ordeal.

Now that the problem is resolved the motor is running great and I am very happy with it.

 

[gandydancer]

Re:Oil in the cylinder. Tohatsu 6 hp 2004

Re:Oil in the cylinder. Tohatsu 6 hp 2004

We have sold dozens of 4/5/6 4-strokes, and have not had one in-warranty oil pressure problem. These beaters are almost indestructible. Troubleshooting the actual issue (rather than guessing) will be the way to go. Either the oil pressure is indeed low, or you are getting a false indicator. A mechanical shop gauge will remove all doubt, since it will prove the exact oil pressure.

Once you determine whether you actually have correct oil pressure or not, you will know what issue to address. If the pressure is indeed low, then mechanical repairs are called for. If the pressure is correct, then you are getting a false indication, and electrical service is called for. Pretty straightforward.

What did the mechanic do, aside from not fixing the problem, suggesting you ignore the warning light, and yet charging you? What is the actual oil pressure, as shown on a shop pressure gauge? Was the dealer able to reproduce the problem in the shop? See if the mechanic will stand by his work, and complete repairs.

Since this is an old tread and I have been unable to figure out how to start a new one, I going to present my question here.
I have a 2004 Tohatsu out board. Yesterday loaded it in my sail boat and pulled the cord, motor wouldn't budge. Pulled the spark plug out and oil began to run out of the cylinder. Cleaned everything off replaced the spark plug, placed the motor in a tank, pulled the starter cord, motor started right up no smoke, no problem. Ran for 10 minutes. Turned it off. Question is how did the oil get into the cylinder. I store the leaning at about a 60 degree angle in th cockpit of the boat, lean on the correct side.

 

[pvanv]

Re: Oil in the cylinder. Tohatsu 6 hp 2004

Re: Oil in the cylinder. Tohatsu 6 hp 2004

To start a new thread, be at the forum listing, and click on the "+ Post New Thread" button to the left.

What is your actual model/serial? Year is irrelevant for servicing Tohatsu outboards.

Oil in the cylinder would cause liquid lock. The oil will get in there if the motor is laid down incorrectly. For the MFS 4/5/6, the proper side is shifter-up. More oil will get in there if the crankcase is over full.

 

[TOHATSU GURU]

Re: Oil in the cylinder. Tohatsu 6 hp 2004

Re: Oil in the cylinder. Tohatsu 6 hp 2004

What Paul said with a lot more emphasis on you putting the power head where it wasn't supposed to go. That can be from laying it down wrong like Paul said, but it could also be from when you pick up the engine and raising the lower unit higher than the power head. That can occur when you take the engine off the boat to carry it. People tend to hug the power head with their belly and swing the lower unit up into the air...Gravity becomes an issue and the oil flows into the combustion chamber.