HPDI ISSUES

[Rosstafari]

So here is the deal... I have been getting to know my new 265 express over the past few months and have been learning a lot of about these hpdi engines. So I had the engine cover off last monday because i was adjusting the idle screw due to the fact that the port engine was idling a bit lower then the starboard and was causing the motor to cut out. when i started her up to check my work i noticed some water in the bottom of the cowling, after a quick look around i could see water spraying out of the back of the poppet valve cover. Once I shut it down and looked further into it I found that the poppet valve cover had a huge crack in it and i could actually see the spring on the inside. After making an order from my local Yamaha dealer i took the valve cover off this afternoon to discover MAJOR corrosion issues at that valve cover. it was so rotted out that when i removed the 2 bolts that hold the assembly together it literally started to dissolve in my hands. Thats when i discovered an even bigger problem. The outer exhaust cover has so much pitting and corrosion where the valve cover needs to seal with the gasket that there is no way a new cover and gasket will seal properly without spraying water out. So after a long night of research on the internet i have figured out that i need to remove and replace the outer exhaust cover to properly remedy this issue. so in the end to make this problem go away i will end up replacing the outer exhaust cover and gasket, the poppet valve cover and gasket and the entire poppet assembly. I will make arrangements with my marina tomorrow to have the boat hauled out so that i can begin to break the motor down. The ecu will have to be removed 1st and Im not taking the risk of removing all these parts while the motors are hanging over the water. I have not yet determined how much all the parts are going to cost but im sure i will be into this one for a pretty penny. I hope that after this fix i can enjoy the boat finally and stop chasing all these mechanical breakdowns.
Here are a few pictures of what im dealing with. any feedback from anyone who has had similar issues would be great thanks!

this is a pic of what i need to replace with the ecu already removed

 

[Grog]

That's a lot of corrosion for a relatively new motor. It indeed looks as if you need to replace the cover but be careful you don't snap any bolts taking the cover off.

 

[ROBERTH]

Looks like some stay current might be causing some electolysis? Would definately replace all anode's. Not sure, think I saw some reference to it but there are also some internal anodes that help control corrosion as well and need periodic changing, especially for those staying on the water.

 

[Tucker]

Please advise developments ross. I've never seen a PRV that clogged and corroded. Hope you have everyting soaking in something. Vinegar, Saltaway, etc.

 

[Rosstafari]

ok here is the update. I hauled the boat last friday afternoon and began to take all the components off the back of the motor to gain access to the outer exhaust cover. I removed the cover and gasket and replaced it with a brand new cover and gasket. i also put a new poppet valve, cover, and gasket on. it was not easy removing all the bolts that held the whole show together but i managed to get it done without snapping any bolts thank god. While the boat was on land I also replaced the VST filter on that sane motor because i was experiencing rpm loss after 4800rpm. I launched the boat today and the exhaust repair was nice and tight with no leaks i was able to get the motor through a good head cycle and re torque the bolts. As fas as the rpm loss issue.... Once i hit 4800 rpms on port i lose power, it slightly bogs down to 46-4700. the other motor is turning up to 5200 WOT. Id love any feedback on this issue.

 

[Tucker]

I think you have problems with the fuel system. Over on THT there is a multi-page thread titled "HPDI Mystery Filters". It is complete with pics about where and how to change several fuel filters. The main one being on your HP fuel pump that is not detailed in the shop manual. The nice part is these guys sourced replacement parts very cheap. The general consensus was then to replace the on-board fuel/water sep to a 2-micron Racor model.

 

[RJTFD]

Did you change the stainless canister filter right before vst pump? If not i would make sure that is done along with the filter element in clear bowl under cowl and also the 2 low pressure fuel pumps which should be changed I think they recommend every 200 hours. The 2 remote water separators also . I never had an issue with the 10 micron Yamaha filters they were rated at 90 Gph.
I had same motors and issues with the loss of rpms when I first got my boat and once I did that all was resolved. Also it doesn't look like he ever changed them valves before nor did he ever flush motors thoroughly I would take a look at thermostats and replace those as well.
Good luck

 

[Rosstafari]

changed the metal filter after the vst tank and sure enough im back in action. Both motors are turning up to 5200! problem solved

 

[fishingFINattic]

Really sorry to hear about the corrosion on the poppit valve -

Regarding the RPM - the exact problem you described is why I would replace the VST, Canister and paper element at the beginning of every season on both motors, clean fuel is super important.

Hope you are enjoying her now...... really missing it this week as I am usually on Block!

Tim