Issue with Mercruiser 3.0

[theepita87]

I recently purchased a used boat. It is a 2006 bayliner 175 with a mercrusier 3.0 I/O engine in it. The problem I am experiencing is that the temperature will rise to 190 while at idle or cruise. If I throttle up a few rpms past cruise the temperature immediately drops to 175. While at any speed above cruise the temp stays at 175. The impeller was changed about 4 months ago and all fluids are normal. Anyone have any suggestions? Was told it could be thermostat or manifold and riser.

Engine Details:
Engine 4111021US Mercrusier 3.0L Alpha
Drive 5121600TS Mercrusier Alpha 2.00:1

 

[Bt Doctur]

Re: Issue with Mercruiser 3.0

inspect/replace the impeller first, then thermostst, then riser .see if the large hose from the water pump to the therm housing gets hard. If it does it a sign of blockage in the manifold or riser.

 

[theepita87]

Re: Issue with Mercruiser 3.0

I looked at the large hose and didn't notice anything out of the ordinary. Can you elaborate more on what I should be checking on it?

 

[achris]

Re: Issue with Mercruiser 3.0

You need to squeeze the hose and questimate the pressure in it. There should be none. If the hose pressurises up, then you have a blockage further down the water flow path.

Chris.........

 

[theepita87]

Re: Issue with Mercruiser 3.0

I squeezed the hose and it felt normal. The spring inside did not feel broken or anything. I plan on changing the thermostat today.

 

[sti1471]

Re: Issue with Mercruiser 3.0

Check this hose for restrictions as well.


When you run the boat on water muffs and garden hose, is there a steady amount of water coming out the water outlets on the outdrive, or is it sputtering/misting out, and increases with throttle?

I am thinking it might be a defective temp gauge/sender.

 

[theepita87]

Re: Issue with Mercruiser 3.0

Check this hose for pressure as well.
View attachment 205818

Here is the diagram for my engine. I made a red arrow point to the hose I checked.


Here is a bigger image without the arrow. the hose I checked was number 12
https://xfer.mercmarine.com/pximages/partscatalog/Common//18858_500.gif

 

[theepita87]

Re: Issue with Mercruiser 3.0

just finished changing thermostat. had to get new plastic sleeve also as old one was cracked.

sadly wont be able to test until this weekend. fingers crossed this was issue.

here is what old thermostat looked like definitively was original.

 

[Bt Doctur]

Re: Issue with Mercruiser 3.0

try this link ,its the large hose from the circ pump to the therm housing.
http://www.boatfix.com/merc/Servmanl/13/13A6R2.PDF

 

[theepita87]

Re: Issue with Mercruiser 3.0

the large hose from the pump to the thermal housing is the one with the spring in it. I squezzed all of the hoses today after changing the thermostat and none of them felt pressurized. Moment of truth will be friday or saturday when I crank the engine up.

 

[achris]

Re: Issue with Mercruiser 3.0

You need to be checking for pressure in the hoses, while the engine is running....

 

[dswi]

Re: Issue with Mercruiser 3.0

just finished changing thermostat. had to get new plastic sleeve also as old one was cracked.

sadly wont be able to test until this weekend. fingers crossed this was issue.

here is what old thermostat looked like definitively was original.

Just a question...Was the piece cracked or was it missing pieces...If pieces were missing, where are they (in the engine somewhere?? Could the posibility of pieces being lodged someplace be impeading water flow?

 

[theepita87]

Re: Issue with Mercruiser 3.0

so was able to run engine today. The upper hose had pressure and the lower hose did not. Replacing the thermostat had no affect on the overheat issue at idle.

 

[theepita87]

Re: Issue with Mercruiser 3.0

I am thinking about pulling the manifold and riser does anyone know if I can do this while the engine is in the boat or does it need to be pulled out. Boat is a 2006 bayliner 175