Gas in my Oil

[Reel Sly]

I'll start at the beginning. Last year I bought a 2001 25' SanPan with a Yamaha F80 (Looney Toons). She needed some serious work. Mostly cosmetic. I'll post my complete restoration soon. She looks like a brand new boat. New vinyl floor and new seats.

Now that I'm done with the cosmetics, it's time to really get out there and have some fun. One of the last things I needed was a new prop. Couple reasons. 1: The old one was really beaten up and 2: I wasn't getting the RPMs at WOT I am expecting. Only 3200 RPMs.

Go figure...the old prop is frozen to the shaft. I rig a make shift prop puller out of some chain and a gear puller. Worked like a charm. The prop is off but no markings anywhere. I decide to call Godfrey. They tell me I should run a 13.5" x 15P. So, today I buy and install my brand new prop. I'm hoping for higher RPMs and for the boat to run great. Unfortunately, that is not the way things work. I get the boat up and running. She is running great but only gets about 3500RPMs. Major bummer. After about 15 minutes or so, she starts to run really rough and stalls at idle. I get her back to the dock and she keeps stalling and my oil light pops on. I get the cowling off and and pull the dipstick. Here is where it gets worse. Oil bubbles out of the dipstick hole. Not thick motor oil but what appears to be oil mixed with gas. At least I hope it's gas and not water. It's about the same color and consistency as my morning coffee. I've been poking around all night on the net trying to find out what's wrong. One post I found said it might be that the motor is under too much load because there is too much pitch.

Does anyone have any ideas?

Thanks in advance for the help!!

[cwag911]

Are you sure it's fuel and not water? Does it smell like gas? You said it looks coffee with cream so that's why I think water.

[Bamaman]

Suggest you post your engine related narrative in TheHullTruth.com or IBoat's Forum. They have many mechanically inclined people chiming in on those websites.

Sounds as if you need a good independent mechanic to look at your boat. It sounds as if your boat reconditioning has gone well, however.

[Reel Sly]

I'm pretty sure it's gas and not water. Smells like gas and it's still black.

I posted on thehulltruth as well. I'm going to pull the plugs this evening and get a compression check. She's going on a trailer this weekend and off to the mechanic.

Thanks for the replies so far.

[rancherlee]

a quick thought, the fuel pump membrane ripped and gas is getting in through that into the crank case (as its operated by engine vacuum). Also I notice its an older carbed engine and its possible that a float is stuck feeding way too much fuel into the engine but it is still seeming to run fine ALTHOUGH 3500rpm with a 15pitch prop is on the low side, should be able to at least spin that up to ~4500rpm with your combo. A 13 or 11 pitch is better suited to your toon.

[LocoCoco]

a quick thought, the fuel pump membrane ripped and gas is getting in through that into the crank case (as its operated by engine vacuum)...

Mine did that. Dealer said the electric fuel pump was "overpumping". The crankcase filled with gas then the motor hydrolocked and skipped two teeth on the timing chain. Took the dealer forever to find the problem since the computer wasn't throwing any codes (and I'm pretty sure they really didn't give a damn anyway). Symptoms were similar to yours, Reel Sly. When first starting it, it ran fairly ok. After running it at rpm and slowing back down to idle it would stall and run terrible. I guess the computer was doing its best to compensate but obviously can't if the timing is so far off.

Hope your problem is easier. Mine was at least under warranty.


LC.

[GregF]

I saw you on THT. Are you really running a 15p on a 25' pontoon with an 80 HP?

[Reel Sly]

Thanks for all the help so far!!

Here are some answers to some questions:

The oil definately smelled like gas and was coffee black in color (no cream). It also smelled burnt

The boat had been running fine so it had been a while since I checked the oil level.

The oil level wasn't just high, it was overflowing out of the dipstick hole.

I bought the prop the Manufacturer told me to buy, 13.5" x 15p. I'll be PO'd if they sent me in the wrong direction. A complete waste of $150.

I plan on pulling the plugs and dumping the oil a few times. I'll report back.

Thanks for all the input

[cwag911]

Thanks for all the help so far!!

Here are some answers to some questions:

The oil definately smelled like gas and was coffee black in color (no cream). It also smelled burnt

The boat had been running fine so it had been a while since I checked the oil level.

The oil level wasn't just high, it was overflowing out of the dipstick hole.

I bought the prop the Manufacturer told me to buy, 13.5" x 15p. I'll be PO'd if they sent me in the wrong direction. A complete waste of $150.

I plan on pulling the plugs and dumping the oil a few times. I'll report back.

Thanks for all the input

Does that motor have carbs and a mechanical fuel pump? If the pump is operated by vacuum, I would remove the vacuum hose and see if there's fuel in it. If there is, then you know where the fuel is coming from in the oil. Rebuild the pump and you should be fine, And change the oil and filter.

[GregF]

A mechanical pump on a 2 stroke outboard uses direct manifold vacuum. It will run like crap with too much gas. On a 4 stroke it runs off the cam and you can get the same "gas in the oil" thing you get in a car if the diaphragm leaks.

I would change the oil and just watch it for a while. If this thing is hemorrhaging gas, look at the pump. Otherwise, welcome to the club pal. There are plenty of 4 stroke making oil stories. I changed mine at 50 hours (6 weeks or so), filter every other change until it stopped. (couple hundred hours in)

There are plenty of theories. So far, knock on teak, my Yamaha is not making oil. It is slower starting tho (making me think it is injector drip/ poor man's choke)

[Bamaman]

+1 on above. 90/10 gasoline separates quickly, and an acid is produced that deteriorates anything rubber.

It's a mechanical fuel pump with springs, etc. and a rubber membrane. You should disassemble the fuel pump and at least putting in a new rubber membrane. Sometimes gas gets past membranes and gets into engines.

If you Google Yamaha Outboard Parts, IBoats has the microfiches online with the parts on the fuel pump assembly diagrammed.

New fuel filters, checking the fuel lines and the bulb would be warranted. Also remove the siphon in the fuel tank to see if there's any blockages or filters.


Then, change the oil and watch the level closely. That engine is just 11 years old and should have plenty of life left in it.

[GregF]

When I looked intro parts, you can get a whole pump for a 60 HP merc for what a kit costs. BTW I have a new spare 60 Merc pump if anyone needs one. Yamaha uses a slightly different pump.

[belercous]

Fuel pump gasket/diaphram is leaking.

[Reel Sly]

Quick update.

Here's what I've done so far and the results. I replaced the plugs and drained/replaced the oil. Also, replaced the frozen thermostat. It took some prying but, finally came out in pieces. Compression check came up with: cylinder 1 = 125, cylinder 2 = 100, cylinder 3 = 105, cylinder 4 = 115. Cylinder 2 and 3 have me concerned. I'm thinking that I might have a leak in the head gasket. I'm definately not the best mechanic but, I'm learning. I'm also in the middle of a Yamaha Ring Free shock treatment.

The results: The motor is running great. It's quieter than before and is peeing better. Thermostat definately helped. I have about three hours on her and she is not "making oil". Did the new thermosat fix this? I don't understand how. RPMs and speed haven't changed. WOT is about 20mph with 4 adults and 3 kids and 3400rpms. On a 25' toon, I'm don't expect much in the way of speed. I'm curious if my tach is off. The prop is 13.5 x 15 and is the factory recomended prop for the boat and motor (I have to beleive the factory knows best )

Thanks to all who posted with advice. I think my plan for the next few outings is to monitor it closely and see what happens. Thanks again. I value all opinions.

[bassn386]

Reel Sly, have you checked your speed against a GPS? Even if it's a portable one ( I have a Garmin Nuvi) it will still track speed. I used mine to check it against the speedo on my Bennington and found out the boat speedo was within 1 mph of what the Garmin said.