Water pressure issue

[janky]

I turned around to look at my motor today it was not peeing very strong. Next time I cranked up I watched it and it spit a sputtered before allowing weak stream to flow. Then once running I had about 14lbs. of pressure then the guage went to 8lbs. then back to 14lbs. It kept going back and forth. Any ideas? New impeller needed? Motor is a 2015 225 SHO with about 95 hours on it? Thanks.

[tracer1]

My 250 does the same thing. Seems to be the usual for the SHO. Crappy WP system IMHO

[ifishinxs]

Sounds like it’s time for a new water pump. You May also have an obstruction.

[tracer1]

Then everyone I know that has a SHO needs a new water pump. From what I understand ( have heard or read ) it is just characteristic of the SHO. Don't know if that's true or not. Seems no one knows either. Yamaha said as long as it's peeing, it fine. Yeah, OK..........Some say to change the poppet valve? Some say don't run it on muff, it will have a weak or no stream at all. I wish someone would come up with a definitive answer on these motors.

[clayshooter100]

The yamaha 4.2L engines don't have a poppet valve (correctly called a pressure relief valve, or "PRV"). It is normal to see more change in pressure than people are used to with older engines. This is caused by the cycling of the thermostats, and the fact that no PRV is used to "buffer" the cooling system. This is normal and not a problem, but of course doesn't mean that your water pump impeller can't be damaged and need replacement.

[tracer1]

Thanks Clay...I know they don't have poppet valves just heard some people say that. My water pressure can be a 20 then all of a sudden drop to 10-12. Then come back up to 20. Even had it stop peeing when running then start again. My Pro XS ( 2 stroke ) threw a stream like crazy & the wp was constant most of the time. Don't know how the Merc 4 strokes are but what I have seen they don't have a strong telltale like the Pro XS either. Maybe it's just a 4 stroke thing but I sure don't like it. To me two of the most important gauges on a boat are the WP & RPM gauge. I watch those constantly, so it really bugs me about these motors. BTW, This the 3rd water pump in the last 2 years because of the crappy wp system. Thanks for the reply.

[janky]

The yamaha 4.2L engines don't have a poppet valve (correctly called a pressure relief valve, or "PRV"). It is normal to see more change in pressure than people are used to with older engines. This is caused by the cycling of the thermostats, and the fact that no PRV is used to "buffer" the cooling system. This is normal and not a problem, but of course doesn't mean that your water pump impeller can't be damaged and need replacement.

Thanks clay. I will probably change the pump kit anyway just for peace of mind.

[woppercatcher]

My 2018 SHO 200 water pressure gauge goes from around 12-18 and back all the time when on plane. Been doing that since day one.

[clayshooter100]

Thanks Clay...I know they don't have poppet valves just heard some people say that. My water pressure can be a 20 then all of a sudden drop to 10-12. Then come back up to 20. Even had it stop peeing when running then start again. My Pro XS ( 2 stroke ) threw a stream like crazy & the wp was constant most of the time. Don't know how the Merc 4 strokes are but what I have seen they don't have a strong telltale like the Pro XS either. Maybe it's just a 4 stroke thing but I sure don't like it. To me two of the most important gauges on a boat are the WP & RPM gauge. I watch those constantly, so it really bugs me about these motors. BTW, This the 3rd water pump in the last 2 years because of the crappy wp system. Thanks for the reply.

It's true that the big yamaha's have a weak tell tale stream, partly because they have very low water pressure at idle and partly because they have a very small line running to the indicator.

Keep in mind that a Merc ProXS 2-stroke (and all optimax engines), must have a strong tell tale stream because the water coming out the indicator hole is the same water that cools the compressor.

[tracer1]

Thanks Clay....I understand exactly and glad I don't have to deal with the compressor anymore. Glad the 4 strokes did away with that. I really like my SHO, good running & best hotshot ever. I just wish the wish the WP issue wasn't as it is. Hard to tell if something is going bad or not. Mine has been doing the same as woppercatcher also.
Again, Thanks

[McQuaig]

My 2018 SHO 200 water pressure gauge goes from around 12-18 and back all the time when on plane. Been doing that since day one.

I'm adding a fitting on my 2018 SHO 200 for tube to gauge. Is your fitting on the lower rear of your motor? pse and thanks

[tracer1]

I'm adding a fitting on my 2018 SHO 200 for tube to gauge. Is your fitting on the lower rear of your motor? pse and thanks

Did you add the fitting yet? What will this fitting do? Post some pics if you don't mind.
Thanks

[McQuaig]

I just did this...it's easy. If you're connecting the tube to an "aftermarket" gauge like Teleflex or Faria (standard on many Skeeters I think) your need an engine fitting (part # MAR-WPRES-AD-TR...$13. from SIM Yamaha). If you're connecting it to a Yamaha brand gauge you will need part #688-83667-00-00 ($30 from SIM). This is a kit which includes a different engine fitting and (smaller diameter) tubing to go to the Yamaha gauge. Either one of these replaces the plug with orange gasket shown to the photo at bottom rear of SHO.

Attachment 349726

[tracer1]

No picture McQuaig, on my end anyway. The hose to my WP gauge hooks up with the fitting on it or does this go to the motor somehow?
Thanks

[tracer1]

Sorry but no pic

[McQuaig]

I'm trying but cannot get the photo to attach...

[McQuaig]

Attachment 349766

[McQuaig]

Geez!!! I can't get this F'n pic to upload. If any suggestions, let me know and I can try again in an hour or so...

[BULLYFISH]

It’s your thermostat opening and closing

[BULLYFISH]

It’s your thermostat opening and closing