04 yamaha 4 stroke vibrate stalls at idle

[rudderz71]

Results from Yamaha rep are in ...
Stuck valve in cylinder #2. Head was taken off and delivered to local machine shop. Rep said it was a first for him. I would have to think that this is a direct issue with crossed wires and running the boat. Still haven't hashed out the details on that. Local machine shops capable of this work? or should have gone new? I didn't get a choice. Update was it was already delivered there. Any issues with that. He claims its pretty standard work. At least we know what the issue is.

[99yam40]

Stuck or burned
either way leakdown test would have shown it blowing through the intake or exhaust.

IMHO Stuck valves do not happen often and I do not know what would cause that to happen and do not know how crossing the plug wires would do it.

Yes machine shops can take care of a lot of things, but we have no real idea what was wrong with your head

[rudderz71]

I believe he said burned valve

[boscoe99]

Stuck or burned
either way leakdown test would have shown it blowing through the intake or exhaust.

IMHO Stuck valves do not happen often and I do not know what would cause that to happen and do not know how crossing the plug wires would do it.

Yes machine shops can take care of a lot of things, but we have no real idea what was wrong with your head

Now keep in mind that a leak down test may not indicate a problem with an exhaust valve that is stuck closed or closed due to cam lobe being worn away. The motor will run poorly but the leak down test may indicate a perfectly good cylinder. Same thing with a scored cylinder wall if and when the score is below the ring line when the piston is at TDC.

A direct compression test on the other hand would more than likely indicate a problem.

One reason why I say a leak down test is not a magical test that can tell everything that needs to be known.

Now a valve that sticks open a bit can certainly get burned which should show up on a leak down test.

[TownsendsFJR1300]

There's no mention of a bad cam/lobe and with the low compression, all indications are of a stuck open valve/burnt valve leaking.

The valve likely burned as the clearance was too tight, wasn't closing fully and heating up. My moneys on the exhaust valve.


*A leak down test would have found this, as posted earlier several times.


That tech, nevermind, doesn't matter at this point. I would have someone qualified re-assemble it, preferably with experiance..

I had a Briggs and Stratton valve (New engine) have a valve hang open. We'd have to let it cool down(gas powered air compressor). Apparently, the valve guides were too tight, not allowing enough oil to lubricate the valve.

In your case, that would not be the issue, it would have happened long ago.

As long as the head itself isn't damaged, it'd be a usual "valve job".

Congrates on finding it, could have been a lot worse...

[99yam40]

I believe he said burned valve

Well Not many of the others have said if they think crossing plug wires can burn a valves in a few hours of running, but I myself would think it is possible.

But then you also say you believe he said, so are not 100% sure.

[TownsendsFJR1300]

It would be nice to know..

Stuck open valves, very, very unusual. Which is what the rep said he never saw. If so, the machine shop should be able to shed some light..

Burnt valve not unusual if not adjusted properly and are too tight. They usually tighten up over time.

For the OP, how many hours on the engine and do you know when the valves were last checked for clearances? If the same mechanic would have done it, please disreguard..

[rudderz71]

Obviously not a mechanic here but I have learned a lot over dealing with this issue. Sounds like the cylinder maybe carboned up due to a miss fire in that cylinder and caused the valve not to seat properly. Not sure if thats defined as burned or whatever but the engine never over heated. I am assuming running the engine for 2-3 hours with variable rpms and sometimes trying wot could cause this. Who knows. I have a hard time believing this could have happened over winter, but again what do I know. I am assuming that they will inspect the head for cracks or warping. I hope its ok. Issue only lied in cylinder number 2. Do you think we should have replaced this head, or is this natural protocol and will be just as good as new. People tell me we should know right off the bat if the rpms are all there we should be good to go. Just worried a little about another set of hands and maybe the cylinder walls not being as thick or along those lines. Again I am no mechanic but can appreciate all the input received here. One of you called it some where along this thread. Kudos! Any other things we should check while we are in there?

[TownsendsFJR1300]

Obviously not a mechanic here but I have learned a lot over dealing with this issue. Sounds like the cylinder maybe carboned up due to a miss fire in that cylinder and caused the valve not to seat properly. Not sure if thats defined as burned or whatever but the engine never over heated. I am assuming running the engine for 2-3 hours with variable rpms and sometimes trying wot could cause this. Who knows. I have a hard time believing this could have happened over winter, but again what do I know. I am assuming that they will inspect the head for cracks or warping. I hope its ok. Issue only lied in cylinder number 2. Do you think we should have replaced this head, or is this natural protocol and will be just as good as new. People tell me we should know right off the bat if the rpms are all there we should be good to go. Just worried a little about another set of hands and maybe the cylinder walls not being as thick or along those lines. Again I am no mechanic but can appreciate all the input received here. One of you called it some where along this thread. Kudos! Any other things we should check while we are in there?

The mechanic that replaced that head gasket should have found it. Either with a leak down test, he didn't do or just visually when the head was off. He saw a blown head gasket, said, ah, that's it and moved on.. I think your fine once the head is repaired. I'm sure they'll maxnaflux it for cracks, etc.

A burnt valve, stuck open valve will leak down, as you've seen, seriously low.

It wouldn't have bothered the cylinder walls unless part of the valve broke off(which it didn't).

Carbon build up can cause a valve to not fully seal eventually leading to poor performance. If bad enough, sure it can keep a valve from seating fully.

Decades ago, before FI, the older cars, 60's 70's, they'd need a valve job usually before 100,000 miles. Carbs, excess fuel, less efficent lead to carbon build up, crappy running and VALVE JOBS.


While on the subject, do you use Yamaha's "Ring Free"?

https://www.yamahapartsandaccessorie...?b=Search&d=34

Its designed to keep the fuel system clean as well as the top end from carbon. Its not cheap but works extremly well.

I run it in every gas machine I own. Expensive, yes. Much cheaper than a valve job, oh yea... Something to seriously consider...

[rudderz71]

Run it religiously for sure! Love that stuff!!
Esp for us northern guys that put our boats away for the winters nap. Says it's good for injectors as well. I usually give a sting dose first then the recommended amount. Def can't wait to get the boat back.

[bajakeith]

Boat mech/tech

After reading this thread thru,, as master marine mechanic would Highly suggest you find a real mech/tech..IMO this guy working on your boat is a Yahoo..and I would be proud to say it to his face...wish you luck .... To TOWNSEND,,btw ya cant magnaflux melted beer cans,,only iron and steel

[TownsendsFJR1300]

After reading this thread thru,, as master marine mechanic would Highly suggest you find a real mech/tech..IMO this guy working on your boat is a Yahoo..and I would be proud to say it to his face...wish you luck .... To TOWNSEND,,btw ya cant magnaflux melted beer cans,,only iron and steel

Agreed with almost all your above post and yes, I was referring to magnetic magnafluxing (which of course won't work with an aluminum part, my duh for the day).

However, something I didn't know existed, some interesting reading: Aluminum "magnafluxing" dying actually;

How to Check Aluminum for Stress Cracks With Magnaflux | eHow

There's other postings re the procedure (although this is the first I've read of it). I would like to think most machine shops would be aware of this procedure..

[TownsendsFJR1300]

Esp for us northern guys that put our boats away for the winters nap. Says it's good for injectors as well. I usually give a sting dose first then the recommended amount.

Glad you use it, BUT, its NOT a fuel stabilizer. Yamaha has a separate stabilizer(looks like the same container-I've never used it).

http://www.amazon.com/Yamalube-Fuel-...AP0KHR4G6RJ0W0

The fuel should still be stabilized, wether it be with the above or another product. Gas Shok works well, I use K-100 and Ringfree exclusivly in the boat.

[rodbolt17]

I agree with Bajakeith.
do yourself a favor.
find a real tech.
like I said, crossed plug wires wont cause a valve issue.

I send my heads to flagship marine in punta gorda FL.
talk to jeff.

5 star don't cut the mustard.

look for fuel , electrical and advanced 4 stroke on the tech's wall.

if it aint there you should not be either.

a leak down test on that engine takes maybe 20 minutes total.
this post should have been over about the time it started.