Honda 50 Gas in the OIL!!

L

little dawg

New member
I have 2000 Honda 50s. The fuel pumps on each engine started leaking fuel into the crank case! Reportedly, the diaphram in the pump started leaking which caused fuel to seep into the oil. I'm surprised the engines didn't fail, but I guess I caught it in time.

Each pump cost about $100. If your engine oil shows a little high, suspect the fuel pump as the cause (don't wait like I did). Also, be sure to replace the o-ring that seals the pump to the engine, if you do this job. It's not too hard of a job but having small hands helps! I also replaced the fuel filter while everthing was apart.
 
Joel, I hope the new fuel pump solved your problem, I had the same problem with my twin 40s but the answer was much cheaper. After checking the pump on a fixture mounted in a lathe, nothing wrong,completly switched manifolds between engines.Port engine was the problem and that didn't make any difference, Was thinking about new engines by now, had the problem for close to a year, lots of oil changes. Was re reading Jay's ( Wyoming ) HUNKYDORY trip to alaska and he had the same problem and cut his trip short because of it.
He contacted Les Lampman, he was told to check the thermostat, that turned out to be the problem and a cheap fix. I talked to Jay and changed mine and problem solved. If that information had come from most anybody else I probably would have laughed at them. Les Lampman knows his stuff!!
I cant really understand the reason, however I have been running in cold water most of the last year and a half, in Maine and winter in the chesapeake. guess its just unburned fuel, now I always have spare thermostats and gaskets in the boat.
Easy to check, just run your engine on a hose and feel the pee stream after a minute or so.
My thanks to Les and Jay who I have never met.
 
RCHINPA":iihng4w2 said:
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I cant really understand the reason, however I have been running in cold water most of the last year and a half, in Maine and winter in the chesapeake. guess its just unburned fuel, now I always have spare thermostats and gaskets in the boat.
Easy to check, just run your engine on a hose and feel the pee stream after a minute or so.
My thanks to Les and Jay who I have never met.
Click to expand...

I had this problem on a Honda Classic 8hp. It was the thermostat, and it was running way too cold in the ocean. Unburned gas getting past the rings, and into the oil. It would be the first thing I would check.
 
Either fuel pump or thermostat long odds on both motors having this issue at the same time.   If changing out the pumps doesn't help hope the thermostats do.   Like RCHIN & Steve said it worked for us.

I like Joel was very concerned about damage to the motor.   When I pulled the dip stick to check the oil there was so much gas in the oil that it came out the hole under pressure.   In the process of Les solving this for me, I questioned him on what he thought about possible motor damage & to my major relieve said  "very much doubted there was any engine damage".  Well that was back in 2007 & I have run many more hundreds of hours on the motors including another long Alaska cruise in 2010 & with 1500 hours now on them they have never ran better.  However I do include two spare thermostats with my spare parts in the boat.

I along with a host of others are true believers in Les knowing his stuff.

Jay
 
Thanks, ya'll. I'm still learning. At least it is cheaper than taking them to the Honda mechanic! haha I'll just replace the thermostats too, just to be sure. I'm going to take one fuel pump apart and see what it looks like. I hadn't noticed the engines running cold. I'll keep you posted.
 
I have a 2003 Honda 50 that also "makes oil". I bought it used about 4 years ago and have had the problem since I bought it. It doesn't overflow but it is always high on the dipstick after running it for a few trips. Les's mechanic suggested that it was probably the thermostat but I could check the fuel pump by removing it from the block (hoses remaining connected) and pumping the bulb. I did this and did not detect any fuel leakage. I then replaced the thermostat and ran it for a week long fishing trip off Vancouver Island. A lot of the fishing trip was running at cruising speed with no trolling. It was still making oil. I took a sample and mailed it in to Blackstone Labs for an analysis and it showed a slightly elevated level of fuel in the oil. As I understand it, based on internet research, fuel can also get to the oil past the rings or from the carbs.
For now I have put the boat away for the winter after changing the oil so I will try again next year to solve this problem.

Any suggestions would be greatly appreciated!

Al
 
They do just what you guys have said. They leak right through the diaphram into the engine oil. And based upon the time I managed an auto repair shop, they can even slowly seep for a long time only to catastophically fail later. I think if I had one that is making oil, I would change it out as it is cheap insurance as one that fails is going to ruin your outboard and could even be a safety risk as you can't plan on when it is going to fail all the way.

While I get the changing the thermostat trick, it will not actually "fix" a diaphram that is leaking - not that Les ever said it would. But the dialog here seems to indicate that it could help. I would assume he recommended that as it could cause the engine to not reach operating temperature and not get the oil warm enough to cook off the fuel that could get through leaky valve seals, valves, and rings upon startup on boats that are only started and rarely actually used. I find it an unlikely culprit, in a boat that is actually ran on the water for hours upon hours as under load the oil gets hot in spite of the cooling system. In fact, it can get damn hot. A kicker through, it another matter entirely.....I'm not even sure they need oil they have so little load on them....LOL...So is a 40 or 50 hp going hull speed. In these cases a good thermostat is very important as engines really do like to be somewhat hot to run correcetly. If it were mine, I'd also check the choke to make sure it is not stuck closed a bit as this could do it too.

Bottom line: If my boat were "making" fuel, I'd be getting to the bottom of it and not using it until it is fixed. That is, of course, you have money to burn as you are reducing the number of hours you are getting out of your outboard because even a little fuel in the oil significantly reduces the oil's ability to protect and lubricate the engine.
 
The thermostat issue doesn't have anything to do with a leaky diaphram on the fuel pump. Rather the issue is that usually the thermostats stick open and over cools the engine. As a result, it doesn't reach proper operating temperature and the piston rings don't seat well. The fuel blow-by is a result of this when the T-stat is working well.
 
I had the same problem with my Yamaha 75 HP, I thought it was a pin hole in the diaphragm too, so I got a new diaphragm I think it was around $30. It is very easy to pull of the fuel pump and open it up and just replace the diaphragm. If I remember right I did the entire job in about an hour or a little less.
But that didn't solve the problem ! Mine turned out to be the thermostat that was stuck and a solid mass of corrosion,but it is also a very easy and inexpensive fix too.
Everything is back to "normal" now and the motor is purring like a kitten !
I hope things work out for the best for you too.
Dave.
 
Guess I better pop in here...

I agree that there are two (likely) scenarios when the engine is "making oil"; either the fuel pump is leaking or the thermostat is stuck open.

Given that there are many hundreds of Honda BF35/40/45/50 engines out there (they've been on the market since 1992) that have thousands of hours on them (some over 5,000) the accumulated wisdom on repairs suggests that it's almost never the fuel pump.

Since the fuel pump is expensive (it only comes as a complete unit) and the thermostat is (relatively) cheap I always recommend checking the thermostat first and typically when folks (or we) do that, it's stuck open. If it wasn't stuck and the engine was still "making fuel" then I'd move on to the fuel pumps.

The reason the thermostat has anything to do with it is operating temperature as mentioned in this thread already. Especially in cold water areas if the thermostat is stuck open the engine runs too cold and unburned fuel is grabbed by the oil ring on the piston and sent to the oil sump.

I'm NOT saying that it CAN'T be the fuel pump, only that it's not very likely and unless the thermostat has been checked first (and replaced if necessary) I wouldn't just jump at replacing the fuel pumps.

Hope this helps...

Les
 
I was going to replace the thermostat in the starboard engine and then see what would happen with a new fuel pump in the port engine and a new thermostat in the starboard engine. BUT after finding that the starboard engine thermostat was stuck open and looked really grungy (see photo), I decided to replace the port engine thermostat. I hope to run them on the lake soon.

I did take apart the port engine fuel pump and found that it seemed to be in good shape, but that there are rubber seals in the unit that could deteriorate and leak if old enough or damaged in some way.

I don't know if I'm adding an image or not. If it isn't shown on this post I will place it in the Wilma Lee folder. Thanks again to everyone's input.

 
Well, I finally had a chance last week to run the engines for several hours and gas is still getting into the oil. Ya'll got any other suggestions?

Both thermostats and both Water pumps have been replaced on the outboards.

Thanks!
 
The only route for gas to the oil is via cylinder, through the pistons I believe. A poorly seated ring or broken oil control ring could be the culprit, but most certainly you would have a poorly running engine. You may have made the comment that the oil analysis showed a little gas contamination. That would not necessarily be unusual if they really meant a small amount. A trace, would not, "make oil." Could it be something as simple as having the dip stick properly seated or measurements hot versus cold? Sounds kinda silly to have you think along those lines, but after the t-stat and the fuel pump, it gets to be pretty mysterious.
 
Well, they seem to be running fine (even better after the thermostats were replaced, or so it seems), but hey maybe I don't know what 'running fine' means! They don't run as smooth as a car or new motors, but seem smooth enough. I usually check the oil cold, like I did this morning and usually make sure the engines are level, although I don't think exactly level or not would make much difference. And I always am sure the dipstick is seated properly before checking.

The oil level is now about 1/2 inch above the level when it was changed. That is after about 11 hours running time, mostly over 2K rpms.

Anyone think taking the engines to a Honda mechanic would help?
 
Never owned a Honda. When I change the oil in my Yamaha with the prescribed amount and after running the engine it will check full. Come back a few days later and when cold it will show a bit over full. (enough that I drained some back out the first time) Start it up for a few and let it sit for a few and it checks full. I think it drains out of the filter after sitting a few days and shows a bit full when cold. A few years back there was a discussion about this.

Does your oil smell of strong gas odor? Does it appear thin? Have you changed it since the thermostat/fuel pump maintenance? Try running the motors for a few minutes. Then wait a few minutes and check oil. See if the level drops to full.
 
Oh, forgot to say, the oil does have a strong smell of gas, but it doesn't appear thin. And I changed the oil after changing the thermostats. Only one fuel pump has been changed, but that hasn't seemed to change anything.
 
Ok I think I can put this baby to rest!

Chris, yes the oil level on the engine when hot were significantly different!! The level when hot was about 3/8 inch below complete full level. When cold the engine oil measured about 3/8 to 1/2 inch above the full level. So my thought on this is that the level of the oil has NOT increased significantly. That means that replacing the thermostats worked and solved the original problem! I'll definitely sleep better tonight!

Many/many THANKS everyone for the help on that.

I attribute the strong odor of gas a couple of days ago to the small amount (I think a small amount can go a long way when smelling something) that would normally get pushed into the oil but is normally dissipated when running the engine at higher rpms. Now when smelling the oil this morning, it doesn't have that strong gas smell. It smells just like the oil on the car oil dipstick.
 
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