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Thermostate installation

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carlnap

Contributing Member
"I have a 2003 5.0 mercruiser

"I have a 2003 5.0 mercruiser 260 bravo 3. Installing the thermostate. correct me if i'm wrong. first u put the gasket to the top of housing then thermostate, then the plastic housing then the gasket in between the two medal housing units, and finally attach all wires and tubes that were removed. I just replaced it and I'm still not getting a temperture. The guage is sitting at 100. I also changed the temp. sensor first to see if that is the problem. Any suggestions."
 
Carl...
Are you sure that you

Carl...
Are you sure that you changed the proper sending unit as alot of these engines have more than one. Usualy there is a sender for the guage and another sending unit for the overheat alarm bell.

Just thinking out loud
Wrench
 
"If you Ground Out the wire go

"If you Ground Out the wire going to the Temp Sending Unit,......
Does the Temp. Gauge Peg out to Hot,..??..??.....It Should....

Also,......
Did the Gaskets you used have the little brass continuity rivet in place,..??..??
Without the little rivet, the sending unit won't get it's Ground......"
 
Thanks Guy. That link was awe

Thanks Guy. That link was awesome and replacing the thermostate sloved the problem. This is the second thermostate I replaced this year. Do you think it's because my canal in very shallow only 1.5-3 ft. I'm hitting bottom docking my boat everytime I use it. Can this cause my thermostate to get stuck wide open. How bad is this for the engine??? Thanks again!!
 
"If you are not using merc. br

"If you are not using merc. brand T'stats, I would start using them since some aftermarket parts are not 100% equal but similar.

If your prop is kicking up alot of sand and silt it could prematurely wear out the impeller and lodge debris in the T'stat forcing it open or in the worst case lodging debris keeping it closed and overheating the engine. Rust in the engine and T'stat assy. will also affect the T'stat.

When your drain your engine block and manifolds do you get alot of junk from the drains that must be dislodged with a wire before water comes out? If yes then you need to pull the drain plugs out completely to help flush the debris out using a hose and muffs.

T'stat stuck wide open keeps the engine from reaching operating temp. and it may not boil off any blowby gases--condensation--from the oil."
 
I was just going to run antifr

I was just going to run antifreeze throught the engine with the muffs. I guess I should drain it and see if any debree is lodge up in the drain plugs. How do I flush the block with the drain plugs open/closed???
 
There are numerous methods Car

There are numerous methods Carl.

One is to leave the 4 plugs out and run the engine on muffs w/fresh clean water via garden hose for 10-15 min. Tilt the trailer so the bow is up to drain the bilge. Keep probing the drain holes if water flow slows down.

Another is to open the drain holes and and shove a garden hose on high into each water hose at the T'stat assy. for 3-5 min. for the exhaust mans. and risers and the water inlet hose from the OD about 5 mins. to back flush the OD and impeller. Then disconnect the circulating pump large water hose at the T'stat and flush thru the hose 5 mins. and the T'stat assy. 5 mins. Tilt the large hose down when done to drain any debris in the curl of it.
 
Guy thanks I'll flush it o

Guy thanks I'll flush it out with the plugs open fpr 10-15mins and check the flow. One more thing. can I use 25w-40 oil in my mercruiser 5.0. I live in NY. How many quarts should you pump into your lower unit after draining before storage???
 
Carl:

Merc. recommends 25W4

Carl:

Merc. recommends 25W40 wt. engine oil for your engine. The OD oil needs to be 85-90 wt. high pressure oil. Stick with Merc.'s OD oil. You'll need about 36 ounces to fill an Alpha One. Pump it from the bottom drain hole until it starts to come out the vent hole at the top. Install the vent screw before installing the lower screw. Install new screw gasket washers. The old ones tend to stick in the screw hole so use a thin blade screwdriver to pick out the old ones.
 
The recommended oil for the br

The recommended oil for the bravo 3 is Quicksilver High Performance gear lube. You most likely have a gear lube monitor mounted on the engine so this drive takes about three quarts. there is a proceedure that must be followed or gear/bearing fail can/will happen.
 
"Drain the drive normally then

"Drain the drive normally then fill from bottom plug until oil comes out vent at top of drive. Install vent plug finger tight. Install bottom plug tightly. Remove gearoil monitor from bracket and dump oil into a container. Clean bottle with clean rag. Refill bottle, install in bracket. Remove vent screw on drive and allow oil to drain until you notice a slight drop in monitor level. This purges air in monitor line. Install vent screw and tighten. Top up monitor to full line. Do not overfill. Install new vent and drain plug gaskets if needed. Check your monitor level after some use."
 
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