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Optimax 115hp Water pump replacement - Walleye Message Central
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Old 03-28-2014, 10:30 PM
jlplitz jlplitz is offline
Join Date: Feb 2010
Posts: 33
Default Optimax 115hp Water pump replacement

In need of some wisdom from fellow boaters.I have a 2004 Merc Optimax 115hp that i bought new back 2005.I have been reading that the water pump should be changed around 100hrs of use.The smart craft guage shows i have 140 hours on the motor,but when using the boat last summer the smart craft guage was showing 2-4 psi at idle and 12-14 psi at full speed and the pee stream was strong.I've been good at doing at doing all the other maintenance on the motor except for dragging my feet on changing the water pump.Do you guys think i'll be good to go the spring since all the water pressure readings were good last year.
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Old 03-28-2014, 10:50 PM
gonz gonz is offline
Join Date: Mar 2012
Location: Central KS
Posts: 331

For me, I would since it sounds like it has never been replaced. It is probably ok, but it is now 10 years old and the rubber is getting older and I wouldn't risk a piece breaking off into my expensive motor. It is easy to replace if you have the impeller and maybe a gasket. If not comfortable doing it yourself, it shouldn't be that expensive at a reputable mechanic. Also, I would check the lower unit grease also if you haven't.

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Old 03-29-2014, 06:30 AM
fishs fishs is offline
Join Date: Feb 2006
Location: .
Posts: 705

Just did mine for the first time on a 2006 150 opti. The kit OEM which included a new housing, couple gaskets and impeller cost around $40.00. Lower unit is quite heavy and should be removed and replaced with 2 people. Good utube clips on how to change. Every thing was working fine I just thought it was time. Impeller looked great but one of the gaskets had turned to mush. Changed the one on my 06 9.9 kicker while I was at it also. Water was pissing out strong on that motor too. That impeller had a fin broke off. Long story short answer. Yes, change it.
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Old 03-29-2014, 05:07 PM
buckwheatNY's Avatar
buckwheatNY buckwheatNY is online now
Slot Fish
Join Date: Dec 2012
Location: Syracuse NY
Posts: 123

I'm getting ready to do mine this spring. Do you know the part # for the 150 Opti. have the motor. Thanks
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Old 03-29-2014, 05:20 PM
outdoorsron outdoorsron is offline
Join Date: May 2009
Location: Iowa City, Ia
Posts: 838

Hello: I would change it. Not that hard to do with 2 people, not real expensive. Like fishs says watch youtube for How to videos. Good Luck this season. O - R
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Old 03-30-2014, 07:11 AM
fishs fishs is offline
Join Date: Feb 2006
Location: .
Posts: 705

2006 150 Merc Optimax OEM part # for water pump kit 96148A8. Double check with your serial number. I would guess that it is the same.

Last edited by fishs; 03-30-2014 at 07:15 AM.
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Old 03-30-2014, 09:44 AM
ohiojmj ohiojmj is offline
Join Date: Sep 2009
Posts: 1,245

For the subject 115 Optimax, the lower unit can be readily removed and re-installed by an able body guy without fear of herniation. Tilt up for removal clearance, remove bolts, slide off, set on work surface. You may need to pry the lower unit a little so have screw drive next to your socket wrench within reach. My LU came off easily on my 2008 90 Opti.
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