Where to get that stupid water pressure sensor.??

mnm99

Well-Known Member
Oct 2, 2015
2,445
Long Island
Boat Info
2004 340 SeaRay Sundancer
Engines
Twin 8.1 Merc
Last year with the new boat and my water pressure sensor started wacking out on one of the motors. SO I figured I'd just buy a mew mercruiser ones for $129 each...and I'll be good for a while. This was last July. Well now I'm back in and one is freaking out again. I talked to a friend and he said he has to change his every year. What the heck..I searched on Ebay and can find them for much cheaper. The problem is a few people I know did that and they didn't work. I'll post back later with the exact part number, but it's on a 2004 8.1 496 inboard if anyone has a better price than $129. Thanks
 
There was a discussion of some alternative parts to merc here:

http://forums.iboats.com/forum/engi...to-mercruiser-sea-water-pressure-sensor/page3

-Kevin

Yea I saw that one. A friend of mine has a 2010 searay with 305's. His sensor LOOKS the same, but works different for some reason. Maybe voltage specific per engine design. This is the one for my boat.

881879T11 http://www.marineengineparts.com/mercury-marine-881879t11-pressure-sensor.html

Here is one on Ebay, but not sure if they would work. I don't see 2004 8.1 on the lists.

http://www.ebay.com/itm/New-OEM-Pre...c1b46e2&pid=100033&rk=7&rkt=8&sd=171533474362

http://www.ebay.com/itm/2x-Water-Pr...c1b46e2&pid=100033&rk=3&rkt=8&sd=171533474362

http://www.ebay.com/itm/Water-Press...4a32486&pid=100005&rk=4&rkt=6&sd=181579738519
 
There seems to be two very similar pressure sensors: one is 0-50 PSI and the other is 0-100PSI.
Maybe that's the difference. I would guess they work the same way just reporting within a different range.

-Kevin
 
These are a pain in the butt. I ordered one using a p/n that I got from Mercury's web site a couple of years ago and the stupid thing didn't work. After confirming the p/n, they sent me a second one. It didn't work either. The symptom was that it indicated 35psi with the key on and the engine not running. The problem turned out not to be the sensor, but I'm worried that it will go bad one day and I won't be able to find a working replacement. My mechanic verified that it was bad by putting it on someone else's engine and he got the same results. I ended up eating the cost of it.
 
This is the sensor they sent me under warranty. Lighthouse marine said it has a 1 year and I bought it last july, so well see how long this one lasts.

sensor.jpg
 
Sometimes particles build up on the sensor and all it needs is to be cleaned up. Happened to me, took sensor out , sure enough there was a barnacle on the tip, wiped it off and put it back into the trans cooler , worked. I will have the replacement part I bought as a spare; I think I paid $80
 
Sometimes particles build up on the sensor and all it needs is to be cleaned up. Happened to me, took sensor out , sure enough there was a barnacle on the tip, wiped it off and put it back into the trans cooler , worked. I will have the replacement part I bought as a spare; I think I paid $80

Every time it was clean. Maybe you were lucky.
 
Ive tried purchasing a less expensive sensors on amazon/eBay and never had any luck with them. I've always ended up spending more money and having to buy the OEM mercruiser part anyway.
 
I've got the exact boat, 2004 with 8.1's, with the pressure sender giving a false reading to the smartcraft. I will buy one either from marine Max, or locally, whichever is cheaper!!
My question is, where is the sensor located. According to one mechanic, it's on the back of the engine over the trans and under the cooler line. A second mechanic, actually the guy that did my survey, said its in the front of the engine on older models and a real pita to get to. Where is it located on your boat and how hard was it to replace. Gonna get to it this week, so I'd appreciate some assistance!!
Thanks,al!
 
If you service your impeller and keep a close eye on the emp gauge then put a resistor bridge in place of the sensor.Never had them on older motors and sure dont need them on the newer ones.
The GM oil pressure sensors that use the 3 wire system work just as well for water pressure too.
As far as location, power steering cooler/ trans cooler, on the rear of the raw water pump
 
I've got the exact boat, 2004 with 8.1's, with the pressure sender giving a false reading to the smartcraft. I will buy one either from marine Max, or locally, whichever is cheaper!!
My question is, where is the sensor located. According to one mechanic, it's on the back of the engine over the trans and under the cooler line. A second mechanic, actually the guy that did my survey, said its in the front of the engine on older models and a real pita to get to. Where is it located on your boat and how hard was it to replace. Gonna get to it this week, so I'd appreciate some assistance!!
Thanks,al!

On my 2004 340SDA with 8.1s it is located on the water pump housing. Starboard side is easy - Port, well... not so easy.

-Kevin
 
If you service your impeller and keep a close eye on the emp gauge then put a resistor bridge in place of the sensor.Never had them on older motors and sure dont need them on the newer ones.
The GM oil pressure sensors that use the 3 wire system work just as well for water pressure too.
As far as location, power steering cooler/ trans cooler, on the rear of the raw water pump
Do you have that part number for the oil sensor? For some reason the only one I found that works it the expensive one they sell. Are you 100% sure the oil one works? They look all the same , but aren't.
 
Anyone hav a video how to bypass this PITA sensor.
 

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