300HPDI with water in cylinders

Gringo · 07-04-2009, 01:47 PM

deleted

SIM · 07-04-2009, 02:01 PM

gringo,

First thing you need to do is stop using it until you get it figured out.

Water can get ingested a few ways. If its not a head gasket leaking water in, it either comes in via the exhaust from backing down, stopping to fast, or via the intake air. When you are underway is there any saltwater that is sprayed up on the cowling continuously? Any livewell water drains in front of the engine?

Andy

Gringo · 07-04-2009, 02:41 PM

deleted

SIM · 07-04-2009, 02:45 PM

Are the cylinders with the saltwater infested plugs the lower ones?

Andy

SIM · 07-04-2009, 03:14 PM

I saw the pic.

If they are the "worse ones" then I am assuming that you are getting saltwater in all of them?

Is there a lot of white crusty salt spray debris on the powerhead itself? If you take off the air silencer box on the front of the engine, do the throttle bodies(where the air goes into the engine....where a carb would would be on a older 2-stroke) have any salt debris or corrosion there?

Dunk · 07-04-2009, 04:11 PM

Why would water foul the plugs?? Typicaly water will steam clean the plug almost like new.

Bullshipper · 07-04-2009, 06:14 PM

Cowlings drainwater through their base above water, and water will come up through the same holes if submerged, right?

So are you saying that the engine is actually going part way under water and then sucking that water through the lower air intake prior to getting up on plane every time?

Is the bottom of the keel so low for the single in the center that you had to use the bracket to mount it extra low? Its a 30" shaft, not a 25" shaft, right?

Sounds like you need a Jeep snorkel and a bottle of rum.

donsmarine · 07-05-2009, 06:26 AM

If you throw enough water on the fire it will eventually go out ,just like a spark plug!Then the plug will foul,water doesn't burn.

Bird Rock · 07-05-2009, 09:11 AM

Can't help much but those engines were known to have water intrusion issues. So much that yamaha made a water intrusion kit for the 250 and 300 hpdis. We have a 300 on a bracket and I've noticed that the cowling is close to the water when you throttle up and come off plain (when the following wave washes up. I will actually turn the boat slightly to the left or right when coming off plane quickly so that the wave doesn't wash directly up on the motor.

Good luck!

SIM · 07-05-2009, 12:38 PM

Gringo,

By whatever means, you need to determine "how" the water is getting into the engine. Whether its cylinder head related(crack-head gasket ect), or its being ingested via the intake air, or its getting in via the exhaust from the actual sea water level.............or a little of all.

My gut feeling is since its multiple cylinders on either cylinder bank, I would be looking at the ingested route. If the water level is actually being brought higher then the cowling seal(where the top cowling meets the bottom cowling) then those two lower cylinders could have water at that same level since they are physically below that seal area. Sure the exhaust is going to push the water down, but there is a very slight time frame when both intake and exhaust ports are open and its feasible that salty air could make its way back in.

Nothing you can do about it now, but a 30" shaft length engine would get that power head farther/higher from the water, but the bracket would have to be raised ect.

As far as engine trim, if it was me at all times without a doubt, I would come onto plane with full engine down trim. Then once on plane trim up as needed. The faster you get the boat on plane, the father/higher the engine is from the water.

I would highly suggest getting your self some new spark plugs. Those dual electrode types are finicky and I can't imagine they are working anywhere near correct with that salt debris I saw in that one pic.

Andy

Freeebird · 07-05-2009, 12:57 PM

I'm no expert, but if it's ingesting water through the air intake, why are only the bottom cylinders affected? Seems to me that would affect all of them the same.

As for that bracket, it certainly looks to me like it's placing the engine too low given how far that one sets the engine back. Have you considered putting a jackplate on the bracket to raise the engine while using the same mounting holes in the bracket?

debugger · 07-05-2009, 01:33 PM

Quote:

Originally Posted by Freeebird

I'm no expert, but if it's ingesting water through the air intake, why are only the bottom cylinders affected? Seems to me that would affect all of them the same.

As for that bracket, it certainly looks to me like it's placing the engine too low given how far that one sets the engine back. Have you considered putting a jackplate on the bracket to raise the engine while using the same mounting holes in the bracket?

Because the air intakes (throttle bodies) for the bottom cylinders are at the bottom of the cowl which are the most likely to pick up water in the cowl.

Put a towel in the bottom under the air silencer and go run. See if the towel is wet and you'll know if water is indeed getting in.

eggsuckindog · 07-05-2009, 02:05 PM

That motor looks mounted WAY too low, which is probably why it doesn't plane better. Like Dunk mentioned water normally doesn't mud them up though, what is your oil usage - those also have a recent oil pump recall - why too oil usage and even after they still seem heavy, could it be carbon??

debugger · 07-05-2009, 02:24 PM

Quote:

Originally Posted by Gringo

I really appreciate all the help, and the questions have gotten me thinking about different things. SO much so that today I went down to the boat (this is not as easy as it sounds) to take a look. I also took some photos. I have a smoking gun. But this is what I did.

First off, I took the air intake cover off. I all the intakes look pretty clean to me. I could find NO evidence of salt water being in contact with the lower ones.

I mean, that looks pretty danged clean, right? No corrosion. No big salt deposits, etc. All I could find inside the intakes was a little bit of 2 stroke oil, which I assume is intentional.

That just doesn't look to me like it's seen a lot of water, if any.

I looked at the cover itself, and notice that the water level would have to be halfway up the level of the lower intake to really get in there.

So, moving right along, I took all the plugs out to take a look at them. After replacing the two lower plugs yesterday, we limped home about fifteen miles with it running really really rough. I could not find severely fouled plugs today. This is one of the upper ones. It does have some sludgey stuff building up on the corners where the electrodes attach to the plug body, but not enough to foul them.

So, while all the plugs were out, I had La Gringa crank the engine over while I watched for any water coming out of the lower cylinder spark plug holes. Nothing that I could see. I reinstalled all the plugs and started the motor. It has always run ragged when it's cold. But the water temp here is near 80 deg, so it's never really very cold. It does take a while to run smooth, though.

While it was running I crawled around where I could see between the lower cowling and the engine. There was water in there! This was a foot above sea level, just at idle. At first I thought maybe the little hose had come off the fitting for the pee hole, but that was not it. I got my fingers in there and felt water gushing against them. I even held the camera back there and got a short movie, but I don't think I need to post it. I turned the engine off, climbed over the top of it, so that I could look directly into the inside of the cowling. Upside down, of course. And I found this bit of Yamaha gray metal bouncing around on the end of a spring, like the head of a jack-in-the-box. Here's a photo, turned right side up:

So, I don't even know, yet, what this thing is. But it's broken, and water gushes out of it when the engine is just idling at 600 rpm. I can imagine what it's like at 4000 rpm. Must be like a firehose in there.

So, what is that? It's got a spring, and it's a removable housing. Is that the thermostat? If so, it could explain some things, like the rough idle til warmed up.

Does this explain how water could get into the cylinders? I have not been able to find a diagram online yet that identifies this. It's on the right side of the motor, looking at the back.

As for the mounting height, I got a photo of that, too. Actually I wanted to write down the model number ( there are four HPDI 300 models come to find out) but I didn't have anything to write with. BUT I had a camera. SO I got the model number, and a photo of the top mounting bolt. It doesn't go any higher on this mount.

So, that's where I am at the moment. Hoping that the busted whatchamacallit is the extent of the damage, and thinking seriously about a jackplate.

Oh, and while at the boat I took the grease gun to all the tilt pivot points and the trim and tilt works just fine now.

That would be a blow thermostat housing. Yes, you found a major problem. The engine probably was ingesting water thru the intakes. Which is why the problem just started. It might be mounted too low but that wasn't the issue.

lostsinker · 07-05-2009, 02:30 PM

Quote:

Originally Posted by debugger

That would be a blow thermostat housing. Yes, you found a major problem. The engine probably was ingesting water thru the intakes. Which is why the problem just started. It might be mounted too low but that wasn't the issue.

That might be the poppet valve. Easy to replace. That's the problem

SIM · 07-05-2009, 02:30 PM

Saltwater muds/goo's them up similar to the pics that Gringo posted previously. Got something to do with salt and the oil. I took the liberty of emailing Yamaha US the pics on Gringo's behalf, and they also verified......saltwater.

Gringo.....that pic looks like the poppet valve assy(water pressure valve). If its physically located on the aft end of engine, way down low beneath the ignition coils, ECM and injector driver, then that's it. You need a new poppet valve cover and you might as well replace the spring-plastic valve-grommet while you are doing it. I have never seen one break, but their is firsts for everything I guess.

What that valve does is release/regulate cooling water pressure at higher engine rpms. I can't imagine the amount of water that is coming out of there, but since the spring is still intact that means the plastic valve is still sitting on the grommet inside the powerhead. Maybe its not leaking as much as one would think. Here is a link to the poppet kit minus the broke cover. http://www.simyamaha.com/VALVE_p/60h-12416-00-00kit.htm

You also are going to want to take the back plastic cover off and check out those electrical components on the back of the engine above that poppet assy. You have some big $$$ electrical stuff mounted back there, so lets make sure its all clean.

Dunk · 07-05-2009, 02:31 PM

That plug doesn't look like it has water on it to me... That's popet valve the waters coming out of. Yam calls it a water valve. With head of hanging out like that I can't understand why the engine isn't over heating. I would think the block would be draining before the water pump pushed water to the tops of the water jackets.

The popet valve opens at around 2000rpms to let water free flow thru the powerhead. Under that rpm the tstats keep the engine hotter so it doesn't fowl plugs.

Have the water valve fixed.. I've never seen one do that..

debugger · 07-05-2009, 02:38 PM

Quote:

Originally Posted by lostsinker

That might be the poppet valve. Easy to replace. That's the problem

Yes sir, poppet valve not thermostat. Housings look the same. Easy and cheap fix.

SIM · 07-05-2009, 03:12 PM

The other item I would check is the resistors on those two lower plugs caps. The 90 degree plug fitting has a internal resistor that can be ohmed out. You unthread that plug from the wire and ohm it out.

That poppet cover is used on many of 2-stroke Yamaha models. If the local guys have any carbed V4-V6 Yamaha's laying around for parts motors, the info I show for that part..... they should be the same part.

Didn't you have a older carbed Yamaha that took some Hurricane damage way back? I recall reading that.

SIM · 07-05-2009, 03:57 PM

It should be the same part Gringo. If the spring, valve, grommet and cover gasket are in good shape, re-use them in lieu of the 150's (which should also be the same). Yamaha had a design change and chances are the plastic valve on the Z300 will be different then the older 150's.

There is a paper gasket on the housing. See if you can save that somehow on either engine.

Andy