2006 HPDI 250 #1 cylinder problem

[jdavis1705]

I have a 2006 250 HPDI that I had rebuilt about 30 hours ago. Number 1 cylinder had frozen and required a sleeve in the block. Motor runs perfect with now about thirty hours on it. Number 1 plug always has a dry black carbon coating on it, all other cylinders the plugs look perfect. I had the injectors gone through and have pulled the reed plate off to check, all the factory reeds are nice and tight to the reed cage, however they do seem to have a bunch of oil around them kinda making them hold a little vacuum when you lift them with a fingernail. YDS says it has overheated in the past a few times , but not since the rebuild. Any thoughts on other possible test to run down this problem ?

[ausnoelm]

Only guessing here, but, I would say whatever cooked your motor the first time is still bad, and another rebuild might be in your future.

[99yam40]

Hopefully Rodbolt or boscoe will be able to give some info on why #1 piston would have black dry carbon on the spark plug

[jcclub47]

How many hours are on the motor since 2006 ? Did they do the exhaust stack when it was rebuilt 30 hours ago ? Same thing happened to my 2005 150 VMAX.

Joe

[pstephens46]

Only guessing here, but, I would say whatever cooked your motor the first time is still bad, and another rebuild might be in your future.

Good point here. I assume the OP is concerned for the same reason....

Apparently these HPDI motors are tricky based on forum and real world examples that I have seen. Lots of reasons given. Bad fuel, over propping, hammering throttle, etc. Anybody out there have 1000+ hours on one of these with no major work?

[jdavis1705]

Only guessing here, but, I would say whatever cooked your motor the first time is still bad, and another rebuild might be in your future.

Yep, thats my fear

Hopefully Rodbolt or boscoe will be able to give some info on why #1 piston would have black dry carbon on the spark plug

I hear Rodbolt is the Yammie expert

How many hours are on the motor since 2006 ? Did they do the exhaust stack when it was rebuilt 30 hours ago ? Same thing happened to my 2005 150 VMAX.

Joe

The Motor had 360 hours when it popped a cylinder, seems like a lot of them lock up about then. Don't think they did anything besides the powerhead. Are you talking about a cracked Exhaust tuner or maybe the Muffler ? I have heard of some issues with the exhaust tuners, tell me more?

[pstephens46]

Bass boat? I assume?

What pitch is the prop?

Just curious.....

[jdavis1705]

Bass boat? I assume?

What pitch is the prop?

Just curious.....

Skeeter ZX250 Bass boat 27" yammie prop. pops out of the hole and runs 68mph gps at about 5300, never opened up anymore than that. Seemed like to much prop to me, Skeeter has a performance bulletin showing that to be the best prop. Although it seems there is more throttle left.

[jdavis1705]

Skeeter ZX250 Bass boat 27" yammie prop. pops out of the hole and runs 68mph gps at about 5300, never opened up anymore than that. Seemed like to much prop to me, Skeeter has a performance bulletin showing that to be the best prop. Although it seems there is more throttle left.

After a little thought I think that was 5750 RPM at 68 mph with more throttle left.

[jcclub47]

I never really found out why I scored my cylinder wall, only good guesses. I had salt impacted in my block and exhaust plates possibly causing the motor to run hot. I also had severe corrosion in my exhaust guide losing back pressure on the muffler I rebuilt the exhaust stack and cleaned everything up real good. If you are running fresh water it should not be an issue for you. I would shoot that cylinder with a infrared gun to see if it's 20 degrees hotter than the rest of them. If it is, stop running it and figure out why.

[jdavis1705]

I never really found out why I scored my cylinder wall, only good guesses. I had salt impacted in my block and exhaust plates possibly causing the motor to run hot. I also had severe corrosion in my exhaust guide losing back pressure on the muffler I rebuilt the exhaust stack and cleaned everything up real good. If you are running fresh water it should not be an issue for you. I would shoot that cylinder with a infrared gun to see if it's 20 degrees hotter than the rest of them. If it is, stop running it and figure out why.

Mine has always ran in fresh water. Shop said they didn't see any signs of water intrusion anywhere. Did you have to pull the powerhead to work on the Exhaust or can you drop the lower unit and get to it all from the bottom? Good point on checking the cylinder temps.

[99yam40]

cannot get to anything by dropping lower unit

[jcclub47]

The exhaust plates are behind the CDI and are pretty easy to get to. I doubt you have any issues there if it's always been run in fresh water. The exhaust guide connects the powerhead to the lower unit and I burnt a hole in mine just before it dumps out the 2 rear exhaust holes, you should be able to see if it is corroded by looking at the flat area on the exhaust guide. Hope this helps.

Joe

[jcclub47]

BTW, I'm just guessing here. When I cooked my cylinder I fried my exhaust guide by spitting fire into it and rendering my exhaust guide to the extent that the cylinder did not have the proper flow characteristics it was designed to have and fouling the plug.

Joe

[cpostis]

Joe, you may be interested in this post regarding the O2 sensor.

http://www.yamahaoutboardparts.com/f...s-th27826.html