Yamaha 300 HPDI 2005-2006 Waterpump

[pjlexydaddy]

I ordered the manual for this engine but did not receive it yet and are impatient. Is there anything special I should know about while replacing the waterpump on this engine? I am assuming it is located in the traditional location which is above the lower unit therefor I need to seprate the lower unit from the engine then slide it over the engine shaft? Are they located somewhere else on these new engines?

Thanks,
John

[Ken]

John,
Check the diagram for your motor in the online catalog above - you will see that the water pump is still in the traditional location.
I am curious - why are you replacing the water pump on a new motor ?
Ken K

[pjlexydaddy]

I have a water PSI issue and dont want to bring it to a yamaha tech and lose 3 weeks of summer fishing. I want to cover a few basic troubleshooting procedures before dropping off the boat to be serviced.

Thanks again,
John

[Ken]

John,
A "water PSI issue" ?
At idle, you should have around 5 psi, and anything above 3000 rpm, should be in the neighborhood of 20 psi.
What are your water pressure readings?
Ken K

[BoatmanDan]

Im having the exact same problem!!! I have a 2005 Z300TURD. With less than 20 hours on it. I have 2psi at idle and 4psi at 3500rpm. I replaced the entire water pump, impeller, housing, woodruff key, even the gaskets with no results. Same pressure. Some one on this board did have some good advice and commented on checking the Pressure Relief Valve. Some debris can get between the rubber seat and the popit and cause it not to close completely. Makes sense to me if the Relief Valve is stuck open you arent going to get the pressure, but you would still see the flow at the pisser. You see, I have good flow at the pisser when running anything above 1000rpm but at idle it just pisses a little. The pressure relief valve is located at the bottom the block if your facing the back of the motor. But let me warn you!!! It is a spring with a plastic popit that seats against a rubber bushing that when the pressure reaches 20psi or more, it pushes on the spring and opens to bleed off the pressure. Sounds simple enough. But it is located in a position that requires the plastic covers under the motor cover to be removed. I had to remove the right bank of plug wires and push up on a wiring harness at the same time while I had my hand on top of the engine exuast plate trying to remove the bolts to see the prv. And once you get the cover plate removed there is not enough slack on the discharge hose for you to get a straight shot when you install the new valve. And you have to hold down the spring and the plastic tip with one hand while you line up the installation all while your trying to get a bolt started!!! Very poor design. I bet needless shop hours and money are wasted on checking or replacing this $3.00 Yes thats three dollar valve! You will need some fancy socket swivels to even think about getting to the bolts. And after all that... I still only have 2psi at idle and 4psi at 3500rpm. And yes I did check the gauge..even removed the hose from the gauge and blew back to the motor to see if I had a blockage. I could blow through it with no problem. I even followed the line back to the engine, its connected to the top of the block above the right cylinder bank. I removed the two bushings and looked down into the engine..its clean as a whisle. I also checked the height of the cavitation plate on the lower unit in relation to the bottom "V" of the boat. It is perfectly lined up parallel. So Im at my wits end!! And your right about the three weeks of missed fishing...my shop told me it would be 5 weeks before they could "LOOK" at mine. Plus they are no help at all over the phone. They cant charge you for a phone call so I dont get any advice from them. I would like to talk to you or anyone else that I share Idea's with on this subject. It cant be that complex. Its the same water cooling design that have been used for 50 years!!! Any Idea's from anyone?????

[Ken]

Dan,
I have read back over your two posts in regard to your water pressure readings being low.
You have done everything correctly as far as I can tell, and you have checked almost everything.
I'm going to assume your pump is doing its job - you are getting no overheat alarms, right?
If you indeed had only 4 psi at 3500 rpm, I would think the motor would overheat pretty quickly.
The only thing left is the water pressure gauge itself - not likely it has gone bad, but there is nothing left you haven't checked .
Would be nice if you could get another gauge and hook up to that tubing just to compare.
Let us know what you find out [img]smile.gif[/img] ,
Ken K

[BoatmanDan]

Ken you would think I would be getting the overhear alarms but Im not. I will try the new pressure gauge and see if I have a defective gauge. But I was thinking....Is there anywhere on the motor that I can install a pressure gauge?? I want to know the true water pressure inside the engine. I was thinking about installing one on the 1/4 inch NPT fitting thats leads to the dash board gauge. Any one done this before?

[pjlexydaddy]

At idle my psi is 0 and at 3500 its about 5psi. The motor continually pisses like a race horse at all rpm ranges including idle.
I may have found the problem.- The tube running from the engine to the PSI gauge may be crimped somewhere simply because I can barely blow thru it and no water made it to the gauge. I took the hose off at the engine and plenty of water shot out of the engine head and when I placed the hose back on no water came out of the other end into the psi gauge.
I will confirm this by running a new hose from the engine to the gauge tomorrow night. I will keep you posted.
As for the one time by buzzer went off indicating overheating- I have no explanation.

Thanks for all the help.
John

[pjlexydaddy]

To BoatmanDan,
You may have a hose problem or a pinhole in the hose somewhere. I would first take a 1 foot piece of hose and connect it to the head then connect the gauge directly to the small piece of hose. (This is what I'm doing tomorrow night)
If that doesnt work and your motor is an 05 you may need to contact yamaha for any service bulletins. I beleive there was a "water intrusion kit" that needed to be installed to correct water problems and is covered under warrantee.
Good luck,
John

[Ken]

Dan,
I don't think the fitting on the top of the cylinder assy is 1/4" NPT - it's Yamaha's own.
John has a good idea - try just running a short piece of tubing from the fitting to your gauge.
Secure the gauge to the motor with duct tape and/or tie wrap, and run the motor w/o the hood to see what the gauge reads.
You may have the same problem as John - a crimped tubing somewhere between the fitting and the console gauge.
Let us know what you find [img]smile.gif[/img] ,
Ken K

[BoatmanDan]

I will try the short hose with a new gauge and see if there is a problem with the hose or the gauge. I want to know where I might get more information on the service bulletion in regard to water pump pressure??? Anyone know? Thanks

[pjlexydaddy]

Contact yamaha customer service(1-866-894-1626). Have your serial number and model number in hand. They should let you know if any updates are needed. Let us know if the tube was the culprit. I have not had a chance to replace mine yet.
1-866-894-1626.

Thanks,
John

[pjlexydaddy]

Unfortunately, running a new hose didnt help. I will need to take it to the dealer for further analysis.

Thanks for all th help.
JOhn

[chuy]

Dan
which side that mushroom head popit goes

Chuy

[1d10t]

I know of a couple of 300's that were MISSSING their exhaust gasket at the lower unit. This was causing an overheat condition... somehow...