how does water get into a cylinder?

[Gringo]

Well, I continue to have issues with a 2006 yamaha 300 HPDI. It had about 85 hours on it when we got it, already bolted to the back of a Contender 25. It ran fine for about another forty or fifty hours, and then started running rough. I figured it was plugs, since this is basically a new motor. Took the plugs out, and the lower two were pretty well fouled, the middle two sorta fouled, and the top two moderately clean. This is at about 130 hours on the clock.

I replaced the plugs, a new set. About five hours ago. It ran fine with new plugs, although it never did get more than about 4800 RPM WOT. Well, I am convinced the motor is mounted too low, as when I first give it the throttle to get up on plane it basically dunks about a third of the cowling underwater.

Today we were out with it, and it started losing RPM and power. I pulled over to a dock on another island and removed the bottom two plugs, and again they were fouled. Almost looks like mud, caked on. I had not seen plugs like that before. These plugs have certainly less than ten hours use on them, including the four hours we put on today.

We limped home, at between 2400 and 3000 RPM. At the dock I noticed a guy with an impressive box of tools working on a couple Yamaha 250s. I struck up a conversation with him, asking if he knew anything about HPDI's ( No. Nobody here does). So I pulled the two plugs I just removed from the motor out of my pocket and handed him one. He looked at it for maybe half a second, just a glance, and said I had water in the cylinder. No doubt in his opinion, by the way. Another guy there walked over and looked at the plug and said the same thing. Water.

I said (hopefully) "you mean water getting into the fuel" and the guy working on the outboards said "No, it's water in the cylinder. Muy malo."

SO, my question is what next. Nobody here has ever seen or worked on a 300 HPDI. I am willing to mess with it, knowing I probably can't fix it. But where would water get into the cylinders? Spark plugs were torqued to spec, by me with a torque wrench.

Where else? head gasket? Well, it ran fine for a few hours after changing the plugs. So, a bad head gasket wouldn't run fine.

The lower end of the motor does get wet when the contender sticks it's nose in the air going from idle to plane. Way wet. But still, where could water get into the engine?

Exhaust ports? But it ran fine for 130 hours...

Any ideas accepted.

Before I junk a new 300 HPDI and replace it with a Suzuki 250 four stroke....

[Tunaman5]

There are water jackets in the head, and around the outside of the cylinders. If the head is cracked, water may be entering when the valves are open. If you say the inside of the cowl is getting water in, you may be sucking water right into the air intake. Water does not compress, and may have caused permanent damage. Do a compression test first.

[jawz12]

Originally Posted by Tunaman5

There are water jackets in the head, and around the outside of the cylinders. If the head is cracked, water may be entering when the valves are open. If you say the inside of the cowl is getting water in, you may be sucking water right into the air intake. Water does not compress, and may have caused permanent damage. Do a compression test first.

2 stroke engines have reeds,not valves,valves are on 4 stroke engines...

water in the cylinders,bottom 2 yes ???

[Gringo]

Yes, the bottom two.

[RABBITFISH]

http://www.yamahaoutboardparts.com/

Gringo, take a look at this forum site. This is where I get all of my info on working on my outboard motor. I have even had some step by step instructions with pictures from them. I don't know if you already know about this one or not, just trying to help..

Tommy

[southshore30]

r u trolling around in seas or swells? you mentioned the motor may be mounted a bit low on the bracket? when the back of the boat is in a wave when trolling down seas the back pressure of the motor at idle or low speed may not be enough to be keeping water out of the exhaust ports. not reaching full RPM's sounds like you may already have done some damage. definately do the compression test so you know how to contunue with the issues.

[Gringo]

I am hoping the loss of power is because of running on four cylinders. Would it reach full RPM with two misfiring?

[Gringo]

Originally Posted by RABBITFISH

http://www.yamahaoutboardparts.com/

Gringo, take a look at this forum site. This is where I get all of my info on working on my outboard motor. I have even had some step by step instructions with pictures from them. I don't know if you already know about this one or not, just trying to help..

Tommy

hey cool!! Thanks for the link. I can really appreciate a forum like that. I frequent some similar forums for Land Rovers, and there's an absolutely fantastic amount of help and advice out there if one can connect with it.

[southshore30]

it would not reach full RPM with the two cylinders down. Don't keep running it to figure it out. Get it looked at but definately do that compression test of all six cylinders. They should all be within 10 to 15 lbs of each other.
Good luck!

[Questsportfishing]

make sure the duck bill / drains on the engine pan / cowling are clean and no debris are clogging them up. they drain any water from the inside of the cowling. also some engines will take on water during rain storms if you have them tilted up. again make sure there are no blockage in the duck bill drains. a compression test will show you if your leaking on any cylinder though. I'd stick a etek or a suzuki 300 in it's place and sell her off. sorry to be so blunt but I don't know anyone that has had good luck with those 300's and feeding them gas and oil is very expensive. this comes from having two of them by the way... if you haul your boat out take a straight edge and you can figure out where your engine is sitting on height.