Yamaha 300HP HPDI 2006

[pjlexydaddy]

Heeeelp!!
I just purchased a brand new 2400CC Sea Chaser with a 300HP HPDI 2 stroke yamaha. I noticed at idle the PSI gauge is 0 but there is plenty of water pissing out from the piss hole. When I put it into gear and increase RPM's to about 3500rpm the PSI will increase to 5psi. If I go faster it will go back down to 0 but thruout this entire time it is constantly pissing great. yesterday I was cruising at 5000rpm when all of a sudden the buzzer sounded and the RPM's dropped to an idle automatically. I immediatly looked at the piss hole and of course it was pissing like a race horse but the PSI gauge was reading 0. The buzzer went away then I proceeded to 3500rpm all the way home with no problems and the PSI went back up to 5psi because I left it at 3500 and no higher.
Another very important piece of information- My Brother purchased the exact same boat and motor and he is experiencing the same exact problem. The boats are used in deep water with no possible chance of inhaling sand.

Any ideas? I would assume this a problem from the factory.
PS- there both left hand lower units.
Any advise would be appreciated.

Thanks,
John

[1d10t]

I am seeing the same problem on one of my 150 HPDI's. If your unit is new, it's still under warranty....

You probably need to put it on the YDS (diagnostic software). There are several reasons the HPDI's will alarm and go into safe mode (which should be more like 2000 rpm). I wouldn't keep running it until you know what the problem is.

There are two thermostats, temperature sensors and a pressure relief valve that need to be checked... and that's assuming you have a good water pump.

I'm not sure what your pressure should be, but I am sure that someone on here will answer that for you.

I'm installing water pressure and temp analog gauges on my rig this weekend. I've also ordered the YDS software for my HPDI's (It looks like it will be a superior tool for troubleshooting). I'll post again when I figure out why my 150 is doing the exact same thing you are describing here.

Please let me know what you find out on your HPDI...

Thanks,

Robert

[pjlexydaddy]

Thanks for the info. After doing a bit more research I think there are 2 seperate problems. The engine may have been installed 1-3inches too high on the transom thus causing it to overheat when on plane and motor trimmed up. The other problem still stands of 0psi at idle and only 5psi at 3000.

I am tryig to find a local dealer to take a look at it.

Thanks again,
John

[Ken]

John,
Normal average water pressure readings should be 5 psi at idle, and 20 above 3000 rpm.
There are several possible reasons why you are reading low psi:
1)weak water pump

2)pressure control valve, aka pressure relief valve, poppit valve, could have debris in it and is stuck open - fairly easy to get to and inspect

3)no thermostats - some owners remove them (I don't advise) when they start having overheat problems - this will drop water pressure quite a bit

4)water pump sucking air due to lower unit too high in water column - or water pump intake restricted from debris

5)bad pressure gauge or kinked/leaking hose from motor to gauge

But if your motor is new - don't mess with it - take it in for warranty service.
Good luck [img]smile.gif[/img] ,
Ken K