2010 150 Optimax Water Pressure Issue

[Casey Tackett]

So I think I have a wierd issue and don't know much about these motors but I'm capable of fixing just about anything with a little insight or direction. Anyways I recentl;y had the lower unit replaced at a mercury dealer because I hit a rock. Anyways The motor ran perfect before i took it into this place and now that they have changed the lower I have a water pressure issue. Before i go any farther I have already changed out the waterpump again with a new impellar which i did about 20 minutes ago. MY issue is my engine will get up on plane and then shut down from overheating, the main problem is it builds up to about 9PSI and then dumps to about 3 or less PSI and gradually builds back up. to about 8-9... never gets up to 15 at FTL the highest it will build to is 9PSI period. I have water coming out the pee hole just fine, i back flushed it with the water hose. Is there anything else i am missing or should look at. and why is it dumping pressure all of a sudden? If you want give me a call or post a message. I'm supposed to go fishin tomorrow and trying to see if there is anything i can do. Phone number is 501-515-1804

Thanks,
Casey

 

[galamb]

Still have warranty?

The water system kinda has two different parts.

One feeds the compressor and then on to the tell tale (pee stream), the second feeds the heads and then goes out the exhaust.

So if you have a good stream that generally indicates that the water pump is fine (and your compressor is getting cooled) - it doesn't mean the heads are getting any water.

The fluctuating pressure between 3 and 9 psi is possibly indicative of a bad poppet valve. The poppets stay closed below 3 psi and the thermostats do pretty much all the work. The poppet starts to open at about 4 psi and is locked "fully" open by about 9 psi.

However, since you say you can not get above 9 psi, that also indicates you have a water leak somewhere else.

Short of taking it back to Merc (which I would do if you have warranty left), I would first replace the poppet to rule it out.

Other factors to consider - is the motor mounted on a jack plate? Too high a mount will cause it to suck some air.

And ok, Merc did it, but was the lower unit fastened back together properly? - if the "wall of water" normally in the exhaust housing is not high enough (leaking out through improperly attached lower unit), that too can cause water pressure/overheat issues.

Are the water intakes clear - again, maybe the tech left some gunk behind and clogged something up.