2009 9.8 tohatsu mixing fuel and oil

[Easternnc]

I must admit I'm pretty clueless on mechanical issues so I hope to get some idea here what the issue may be. I have a 2009 9.8 Tohatsu 4 stroke with electric start/stick steering-serial number 061044xg. I was unable to start it a couple of weeks ago (it had not been started in 3 to 4 months). Last time it ran, it ran great- no issues. This time it would crank,run for a minute or so and die. I tried many times to get it to run for more than a few seconds without success. Smelled fuel very strongly and the engine smoked quite a bit....which it had never done. I noticed what appeared to be fuel and oil in the bottom on the lower cowl under the carburetor. When I checked the crankcase, fuel mixed with oil spewed out. So off to the repair shop-they tested the fuel pump and said it was good. Found choke not hooked up. They changed the crankcase oil and lower unit oil. And as you would guess, they said the engine cranked and ran fine. That was 3 weeks ago and tonight I experience pretty much the same thing. It cranked on the second try but would only run with the neutral warm up lever wide open. No smoking. Found fuel and a little bit of oil in the bottom cowl. Sure hate to go back to these folks without some idea what is wrong. Bill for earlier work was about 145.00. Any ideas?

 

[pvanv]

If you continue to have LOTS of gas in the oil, the fuel pump is probably leaking into the crankcase. If you can't idle and the oil is not over full, odds are the carb needs Properly cleaned.

 

[Easternnc]

Thanks for the reply and help. I will have someone clean the carb and rebuild if necessary. I may try to replace the fuel pump since it's not very expensive-about $55. That doesn't seem bad and would eliminate that problem which I think may be part of the issue. How difficult is it to replace the fuel pump? I think I have an MFS 9.8A3. Any other parts other than the fuel pump I would need?

 

[pvanv]

3H6040007M

FUEL PUMP, 4/5/6/8/9.8 4-STR ONLY

$63.88

3H6074220M

O-RING

$1.33

You will need a #3 Yes, a BIG phillips screw driver.

 

[Easternnc]

I looked on boats.net site and got a little different part number? Anyone on this site sell Tohatsu parts? How difficult to replace this? I really appreciate your help.

 

[Easternnc]

pvanv: was off this afternoon and had time to do a little more homework. I found two of your posts going back to 2-8-14 and May 1, 2013 addressing what seems to be the same issue I have. So... I have a couple of questions I would greatly appreciate you answering. 1. Engine oil: I have been using Tohatsu 10w-40 outboard oil, a synthetic blend for 4 stroke outboards. You're suggesting 10W-30 NON SYNTHETIC? 2 .Fill crankcase 1/2 way on dipstick? I have filled it to the full line in the past and I believe the dealer did the same thing recently. Should it be run at the halfway point all of the time? Is 3/4 point any better or worse? And I assume the 1/2 levels doesn't cause harm the engine-short or long term? 3. Can I get the fuel pump and o-ring from you? I think I want to replace the fuel filter as well. 4. What do you recommend for a fuel stabilizer-I use Seafoam now. I know you're busy and I really appreciate your time. Thanks again.

 

[Easternnc]

Just curious, what does running the oil at 1/2 full have to do with this problem?

 

[pvanv]

The 4-strokes make oil, so unless you have run hard and hot for at least 20 hours (to seat the rings), 1/2 is a good starting point. After that, 3/4 at oil change is fine. It will slowly rise, and you never want to go over full. Synthetic oil gains more. The Tohatsu blend is fine. Check the dealer locator on the Tohatsu website to find you closest parts dealer.

 

[Easternnc]

What does "make oil" mean? I've always owned 2 stroke until this 4 stroke and never heard that term used.

 

[isaksp00]

In the past, I've found a few pretty good sites that explain it in some depth by searching "4 stroke making oil". Seems to be (mainly, normally) water vapor condensing in the crankcase, adding volume to the oil already in there, because smaller 4 strokes often don't run hot enough to heat the oil itself. Obviously never an issue for 2 strokes.

 

[Easternnc]

Thanks for the response. imagine that...my own oil well. So I guess when the crankcase becomes too full you drain some of that out...to keep it below full?

 

[Sea Rider]

2 strokes OB's doesn't "make oil", you can save some cash if only buying the fuel pump internals, diaphragms related. Check how many are there and if sold as spares.

Happy Boating

 

[ondarvr]

Making oil is from fuel getting past the rings and diluting the the oil, small amounts aren't great, but not terrible either, as more fuel enters the cranckase the oil is degraded and needs changing, not just draining a little out.

This is from low operating temperatures and possibly poorly seated rings, running it hard helps to eliminate the probelm by evaporating off the fuel and better seating of the rings.

Water enters from condensation and if the motor isn't run hard enough to evaporate it, it will remain in the motor and turn the oil into a milkshake consistancy if it's not changed.

 

[Easternnc]

I bought this motor used and have no real idea how hard it was run. I suspect though not run hard for 20 hours. Is it too late to do this? Will it help seat the rings if they aren't seated. So as far as the oil,goes, would it be safe to fill to 3/4 and when/if full, change it?

 

[ondarvr]

You want oil in it, not a mix of oil and fuel, a mix of 75-25 is not what you want lubricating the motor. Make sure this is the issue, check the thermostat and fuel pump, plus try getting it up to the correct operating temperature everytime out. This is a common problem where I live because we use these small motors to troll with for hours on end in cold water, some people put in a higher temp thermostat to keep the temps up.

 

[Easternnc]

And how do you determine the correct operating temperature? Am replacing the fuel pump this weekend and we'll see what that does.

 

[pvanv]

We use an IR therometer to check temps at various locations of the motor.