2003 90hp 4 stroke Yamaha rough today ?

[klbowe]

Not sure what is going on with the Yammi but today she started idling rough at slow speeds. Almost like its missing on one cyl.

If I put it about 1/4 throttle she smoothes out. But as soon as I slow down she shakes.

The engine has 47 hours on the meter and the plugs are original. I pulled and checked them gap is ok about .42 the ceramic on the anode looks a little brown, the metal around the threads has a bit of carbon ? or black crust on it, the anode and electrode to not appear burt up at all. So I do not know if it is the plugs. I really am not sure what they should look like to be honest.

The primer bulb may be suspect. It does not go flat but there is no resistance and you can pump it as long as you want and it will not get hard. (sorry) While I can feel fuel in it it is not like on a small 5 gallon tank where you pump it hard and it stays hard. Is this normal ?

Whats your best guess ? should I take it in or repl the primer bulb and or plugs.

Thanks !

[klbowe]

I forgot one more "clue" ever since I have had the motor it is slow to start if the boat sits 2 weeks without use even if I pump the heck out of the primer there is no manual choke on this motor just a throttle.
If it sits a week or less it pops right off.

[Borch]

Add Seafoam to your gas. Sounds like your jets may be varnishing up. If it's sitting 2 weeks or more at a time it's the likely culprit. Those yammi 4 strokes are notorious for the jets plugging up.

That's where I'd start anyways.

Borch

[mnrstrider]

...and buy a new fuel line, they are cheap, $20 or less. It make a big difference on how well my boat ran. I suppose you could just replace the bulb too, but I did the whole line because it was cheap enough, and much better than the hose clamps I used to keep the new bulb on. I reccomend Attwood brand lines and bulbs, I bought some junky one at FF and it was no better than my bad one, then I replaced it with the attwood and now I can tell the difference.

[This message has been edited by mnrstrider (edited 08-24-2004).]

[Sgt. Rock]

I'll second the seafom idea. I have a 80hp 4strk and it smoothed out the rough idle on it. I also have the bulb issue of not getting hard when pumped. But see no issues yet. What improvement did you see with a new line and bulb mnrstrider?

[klbowe]

The motor is under warranty and so I took it in to the dealer today. They thought it may be a quick fix and so they had me drive it in back. The Mech. started it up and pulled the plug wires one by one, it killed every time a wire was pulled until he got to the last one, number 4. When he unplugged number 4 it kept running (rough) and made no difference in how the motor idled with #4 unplugged. So the problem should be isolated to cyl #4 be it spark, carb, or comp. Right?

He then pulled and replaced the #4 spark plug no difference. Next he removed a plug on the #4 carb and sprayed in some cleaner until it bogged a bit then sprayed in some more, no difference. At that point he said he would try balancing the carbs ??? and if that did not work he would have to pull the #4 carb and clean it.

Also keep in mind that #4 spark plug looks normal, just like the rest.

I run the correct ammount of Yamaha Ring Free and also Mercury Quikleen every time
I fill and fill at busy gas station. I have run 3 tanks this year so I do not think it is stale gas.

The Service Manager did not think that cleaning the carbs would be covered under warranty if that ends up being the fix. I guess I can understand that because bad gas should not be covered by warranty.
But I know I have done all I can to buy good gas and add the required conditioners and additives and I do not understand why bad gas would only affect one carb but I admit I am by no means a outboard mechanic.

I am all ears so PLEASE all you motor heads reply with your opinions or best guess and I will keep you posted.

THANKS !

[wastewaterguru]

Funny how they always find something that isn't covered by the warranty!!!!!!!!!

[mnrstrider]

I'd certainly run a lot of seafoam through before I paid some guy to rip into my carbs, but that's me. Seafoam is great stuff, but then again it might not solve you problem either. Is it possible you just got some bad gas?

As far as the bulb goes for me, my bulb would always lose prime, and in which case it would cause hard starts, if I didn't remember to re-pump the bulb everytime, kind of a PITA, but primairly when crusing a lot at lower speeds, like just trolling along a click above neutral, it would spit and stumble a bit more, never died, just ran rougher, especially when I went to take off, but I never had any issues if I was up and running at a higher speeds. Bottom line is I could get away with it and it would still run, but now it runs better without having to prime the bulb more than once in the begining of the day.

[Surface Tension]

Did #4 have spark? Was the compression checked in all 4 cylinders?

The bulb should get hard. Could be a faulty check valve in the bulb or an inlet valve isn't working for one reason or another in one of the carbs, possibly #4?
Since its under warranty and at the shop you should be taken care of.

One question to ask the service manager. Ask him or her if they would rather clean a carb under warranty or an overhaul from a scored piston.

[Borch]

Klbowe,

I've heard of three people in the past year who had the same issue with their new motor when using the fuel treatments. What was found was that the fuel tand had fine metal shavings in it. Somehow it they made it to the jets and pugged one of them up.

If that's the case you shouldn't be required to pay for it. Just a heads up. Complain loud and long enough and they'll figure oout a way to cover it.

If you're treating your fuel, a dirty carb shouldn't happen while your boat/motor is still under warranty. You fuel treatments will solve pretty much all of what would cause these issues(Varnsihing, water, etc.) Fuel filters should remove all but the smallest particles).

Just doesn't make sense unless you've got the same issue with a metal filing pugging a jet. You'd think that your fuel filter would catch these though.

Borch

[klbowe]

Thanks for the replies.

My wallet will not open easy on this one.

I am just waiting to see how it plays out.

Borch : Did you mean tank? If it is metal filings I would hope that they tell me rather than say it was dirty here is your bill. If they say it was just varnish or dirt I will pull the filter and ck for metal.

SurfaceTension : I did not see him check #4 for spark but it really smooths out as you accelerate could it be missing spark at low rpms only ? Also if the cyl is lean it could cause a scored piston ?
I would hope they check compression but I will ask to make sure they do.

All : I will be replacing the primer bulb and fuel lines to the motor when I get her home.

[Borch]

Yes tank. Darn fingers.

Borch

[WaveWacker]

Similar thing happened to my 75 4 stroke Merc. Didn't run all that well. Service guy did the pull the plug wire trick with the same results. He took the hoses off of each side of the "bad" carb and and shot a little air through the intake side. Put it intake hose back on and squeezed the ball and finally got some gas to come out of the other side of carb. This was after putting in regular 87 octane fuel in and letting it sit for a while.

He told me that if you can find non-ethanol gas that is the best otherwise Amoco Silver is good as well and when you fill with gas throw in a can of SeaFoam. Fortunately the station in town runs 92 octane non-ethanol gas on one pump. I follow this religiously and so far haven't had any problems. Good Luck.

WW

[panolo]

Sounds to me that you could have something in one of the pilot jets. They affect your motor from idle to about 1/3 throttle. Todays gas goes bad in about 30 days or less. I always put in some stabil or sea foam to help perserve the gas. Let us know what the deal is.

Edit:
That is probably why #4 would like fine. When you are going full throttle your main jets handle the job and it gets enough fuel to burn right and cause the plug to look normal. I have never had a problem with a Yamaha warranty. They have always covered everything they should for me. If it is a bad jet you should be covered no problem.

[This message has been edited by panolo (edited 08-28-2004).]

[Surface Tension]

klbowe, Being its a 4 stroke and the problem seems to be at low RPMs scoring isn't as big a concern as it would on a 2 stroke with with a dirty high speed jet.
Let us know what the shop finds out.

[klbowe]

I got the boat back on friday and took it out this morning (in heavy fog). It idles better than ever.

The Service Manager said that the lower carb had "sludge" in it, they cleaned that carb and balanced the rest.

I am still a bit confused how sludge got past the filter and ended up in just one Carb.

He said that Yamaha only recommends Ring Free be added to the gas and not to add seafoam or stabil. I think seafoam is a good additive and will probably start using it after the warranty is up.

There is also some confusion at Yamaha on what gas I should be running. The owners manual says 86 octane or higher and ethenol is ok if it is 10 percent or less ethenol. But Yamaha Customer Relations says you must use 86 octane, no higher, no lower, and no ethenol. So because bad or incorrect gas is not covered under warranty if you have a carb problem you could be out of luck. You have to trust the shop because you are at their mercy.

I am pleased with the repair, they got it done when they said they would, the motor runs great and so far they covered it under warranty. Hopefully sludge won't come back.

Thank you all for your replies.