Outboard confusing issues

[vizwhiz]

We have a Yamaha 9.9 also, and my little pee stream gets pretty hot.
Never noticed fuel in the oil, at least not yet. But it could be a leaky fuel pump diaphragm that is leaking past into the crankcase area where the pump is bolted on. Had a similar problem on a car in the past, not exact, but close. This could also give you trouble at higher speeds, as fuel flow would be low, as someone already pointed out.
My vote goes to fuel pump diaphragm.

[vizwhiz]

Okay, I confirmed what I was thinking. The fuel pump on my Yamaha 9.9 is cam-driven, just like on my old cars.
Essentially, the cam has a bump on it, the fuel pump has a little spring-loaded follower on it. The bump mashes the follower, which flexes the diaphragm. That pumps the gas. I was messing with my engine today, so I took the fuel pump off to see... Here are a couple pics.
In a nutshell, if the fuel can leak past the metal ring in the center (where the follower is attached), it can bleed all the way into the crankcase, filling the crankcase with fuel (mixed with the motor oil that's already in there).
NOTE: Sorry that the pics come out sideways. Not sure what's doing that - it didn't do that before.

[Interim]

That is very useful. It answers a question I have been struggling with.

Thank you.

--john

[fritz3000g]

Update on this issue: the experiments I did (bypassing fuel pump with tank elevated and cooling the fuel pump with water) did nothing. Actually during the test I got a misfire and a little bit of black smoke, which suggests excess fuel.

So... I think that leaves electrical and oxygen issues. Any ideas for what the next thing to check would be?

[Seapup]

So... I think that leaves electrical and oxygen issues. Any ideas for what the next thing to check would be?

From the description and gas in oil issue really sounded like fuel pump.

I kept getting ethanol separation in one of my T9.9s and the separated fuel would stay unmixed resting in low spots like the inline filters and float bowl until it was sucked up at higher RPMS. Another motor I had the interior of the fuel hose collapsing under higher speeds causing the motor to die.

Doubt its it, but the CDI will retard the motor down to 2000 RPM for low oil pressure, you can bypass that by disconnecting the yellow wire on the 2007 newer motors. I think its the same on the older.

Spark can be checked by pulling a plug.

If all else fails central marine has brand new left over T9.9s on clearance for $2400 shipped...

[fritz3000g]

Thanks Seapup.

Like you say, I don't think it's the CDI retarding RPMs. I could see it being the thermostat or CDI (or perhaps the bolt setting) reducing air flow.

I've only ever used ethanol-free fuel in this motor, and cleaned the fuel system thoroughly when I got it.

I've checked the spark. It's possible there's a timing issue, though I don't see why engine temp. would affect that.

Is there another test I could do that would completely rule out the fuel system? I thought I had with the elevated tank test, especially after seeing the misfire and black smoke.

[Capt Smitty]

May I toss in my 2cents? Up front, I'm not familiar with your outboard, but I am with those symptoms. I'd say you've ruled out fuel delivery (pump, tank, hose, etc), almost ruled out carb. You said there is a carb bowl, so there must be one or more fuel pickups, that have small orifices, feeding small passages to idle, part throttle, and wot circuits within, which can become RESTRICTED, thus leaning fuel mixture just a little too much. Could be compensated by cold fuel enrichment circuit (choke?). Should be easy to test, when it sputters, engage choke(s), restrict carbs air inlet (loosely held rag?), or spray flammable carb cleaner into carbs. Fuel in oil can get past perfectly good rings, by washing the slight amount of lubricating oil off of the cylinder & rings. Which normally would be due to extreme rich/flooding fuel, but can be caused by a normal fuel/air mix that does not combust, at all, maybe only every few revolutions? Your last comment about the misfire & little bit of black smoke is classic ignition misfire. A lot of black smoke, then misfire I'd blame excess fuel. But that got me wondering about your ignition system. I know how a spark can be present out of engine, but too weak under certain conditions to maintain, or always begin, complete combustion. So I did a little bit of googling Yamaha CDI, and found, present yet weak spark causing both no starts, and your symptoms. Electrical stuff ( wound coils) often weakens or fails when hot, will work OK cold. One comment I read (I'm sorry I did not save info), was your symptoms, on a t9.9, only when warmed up, due to a slightly corroded ground wire in ignition system. "Slightly, un-noticeable, corrosion" has fooled me before. All that can be tested. Good luck

[fritz3000g]

Thanks Capt Smitty.

Your two cents are most welcome! Thank you so much for doing the research.

So the two tests you suggest are:

• Restrict airflow when sputtering
• Check spark strength

I'm not sure how to check the spark strength, other than to take it to a shop. Do you?

Or are you suggesting I take in the CDI for testing (I don't have the special tester)?

Thanks!

[Capt Smitty]

fritz3000g.
This is all my OPINION. Based on 50+ years as a mechanic, and limited info of your situation. I'm looking online at a Yamaha T9.9W manual.
First off, if you don't have a operators/owners manual, and a factory or after market service/repair manual, get them. Download free, or buy a book. Make sure you get the service/repair manual that covers your yr & model of t9.9, it looks like there were many variations. The factory service manual will give you the specs and locations of things (but not much how-to). I bought a selocmarine.com repair manual for the Nissan 50hp on my . It copies the factory service manual, and throws in a few extra how-to's. Spend the $20 or so on a good aftermarket book, it's well worth it.
Oh yea, the factory service manual has some B.S., you don't need the fancy (expensive) factory tools. Get a VERY cheap VOM (cause you're probably going to kill it), upgrade later. Buy or make a spark checker, see below.
So, the first test I suggested was to finish testing the fuel metering system (carb, intake, etc), specifically for fuel lean out when sputtering, by enriching mixture (remove air, or add fuel). Looks like your carb has a "electrothermal valve" on it, which I think adds fuel when engine is cold. I don't see a air choke valve. Use a can of carb spray, or brake clean, to add a small spray of fuel, directly into intake, as close to carb as you can, when the engine is sputtering bad, preferably under load. Repeat with larger/longer squirts. And pray the engine does not clean up & run great for the few seconds you're adding fuel, carb diagnosis & repair can be much more frustrating than CDI repair.
The next testing I suggested (which I'd do next anyway) is test ignition system (spark plugs; ignition, charge, and pulser coils; CDI unit; wiring & connections). I found a good how-to video https://www.youtube.com/watch?v=MDbvkFM1V_c I'm sure there are others. This guy uses a aftermarket spark checker, and a VOM. My spark checker is similar, made by Thexton. There are others, inexpensive, available. He is working on a different engine than yours, but it's similar. Use his techniques, and the wiring diagrams & specs for your model. Test the easiest stuff first, save the CDI box for last but don't be afraid to open it as a last resort. You are measuring voltages, and the resistances that can affect those voltages, during failure events. Which means warm & under load. I've failure tested electrical parts, sometimes hooked up & working, using hair dryer to heat the component. A lower then spec voltage upstream, will lower voltage at the spark plug. As I noted in my last msg, this guy (Dangar Marine) also found a hidden, bad connection. I've seen so many examples of minimal corrosion creating problems when warm, that I'd start (and did on my engine) by disconnecting every wire, one by one, closely inspecting & cleaning anyways, reconnecting with electrical grease, don't forget grounds, and battery.
Whew! That was longer than expected. But let's not get into carburetors.

[fritz3000g]

Thanks Capt Smitty.

I have a manual and service manual. I followed the SM instructions for rebuilding the carb and setting screw positions which has been helpful. I'll consider getting the Seloc manual too.

I'll start working on the other diagnostics. I'm limited for how far I can go since the boat is now winterized so I can't test it hot under throttle and load, but I can test the ignition system.

Thank you - this is super helpful!

[Interim]

Just an update on my situation (Yamaha 9.9, cold water from the tattletale, fuel in oil), I took it to a mechanic on the theory that the complexity grows with the number of symptoms.

He thinks my fuel pump is fine (he actually tested it). He did replace the thermostat, which was definitely bad, and replaced the power pack because the timing was not advancing. I haven't put it in the water, but he ran it in his shop and said there is significant increase in power. My hope is that better activity in the cylinder will reduce fuel going where it shouldn't.

--john

[cestlavie]

I was also was able to 'create oil' in my 2003 F60. I was told its quite common and You diagnosed it correctly, the fix is normally just new feul pump diaphragm. I was also told it can happen if the thermostat is missing or is running the engine cold, or Valve\ring wear, both issues letting unburnt feul into crankcase.

In my case it was significant, and was feul pump. As a bit of context I'd had the carbs rebuilt twice (me then by dealer) to get rid of a top end bog, and was about to start replacing ignition coils but that issue was fixed after feul pump replacement. A small tear must have got a lot bigger I spose.

Check out Dangar Stu on YouTube , his outboard fix videos are nearly as good as this site for how to diagnose and repair stuff. This one is on the low pressure feul pump similar to what we run
https://youtu.be/_ezu96S7e14

[sailboatmike]

Outboard motors and their manufacturers are one of my pet issues, my 2 stroke auto mixer runs too much oil in the ratio, so I check the setting, sure enough the cam setting is wrong on the oil pump.

One would expect this to be a simple issue to fix, HOWEVER, the air box needs to come off to get to the pump adjuster, that should be simple EXCEPT, the top 4 fasteners are studs, nice and easy to remove the nut BUT the bottom 2 are bolts, bolted through the air box and also hold on the the bottom carby, because the bolts are so long they cant be removed without removing the covers on the leg because the gap is too small between the back of the airbox and the bottom cover of the motor.

What should of been a simple job of undoing 6 nuts, removing the air box and adjusting the length of the oil pump cam arm, turns into a major job or removing the 4 nuts and 2 bolts, removing the motor covers, removing the air box (at which carby 3 will fall off), adjusting the cam arm length, replacing the gasket between the carby and the block for number 3 cylinder and then reassembling.

So basically Mercury have managed to take a 10 minute job and turn it into a 2 hour job just by poor design and for some unknown reason using bolts on the bottom carby instead of studs like they did on the two other cylinders (if studs are OK for the other two carbs why not for the third?). Well I would say poor design but I think they did it deliberately to increase income for their dealers/ service centers, apparently from talking to the outboard mechanic Mercury are not the only ones that do this Evinrude and a few others do exactly the same thing.

[Ixneigh]

May be buy an outboard in the Bahamas or some place, where they sell to commercial fishermen.

Ix

[Seapup]

Just an update on my situation (Yamaha 9.9, cold water from the tattletale, fuel in oil), I took it to a mechanic on the theory that the complexity grows with the number of symptoms.

He thinks my fuel pump is fine (he actually tested it). He did replace the thermostat, which was definitely bad, and replaced the power pack because the timing was not advancing. I haven't put it in the water, but he ran it in his shop and said there is significant increase in power. My hope is that better activity in the cylinder will reduce fuel going where it shouldn't.

--john

Thanks for the update. Once you run it in the spring be sure to let us know if that fixed the problem.