Merc 3.0l Overheats

[brsox88]

I was just running the boat the otherday, ran perfect. Replaced the alternator the day after that since the bearings were going on it. Did a test out of the water with ear muffs of course and it now overheats. Where do I start to try and fix this? Is my impeller gone?

 

[Rocky_Road]

Re: Merc 3.0l Overheats

You did put enough tension on the alternator belt when you changed the alternator?

That belt also turns your engine mounted water pump....

Happy boating!

 

[brsox88]

Re: Merc 3.0l Overheats

You did put enough tension on the alternator belt when you changed the alternator?

That belt also turns your engine mounted water pump....

Happy boating!

That actually may be the issue. It did have a good amount of slack in it, but I was thinking it should have a lot of slack. I have tightened it up.

Also how hard is it to check the impeller and is there any general how to? As of right now, I dont even know where its located.

 

[DJ]

Re: Merc 3.0l Overheats

Go here and find your manual to download.

http://forums.iboats.com/showthread.php?t=288430

 

[brsox88]

Re: Merc 3.0l Overheats

So I tightened up the alternator so there is no slack in the belt. It didnt help. Engine still gets up to 180 and I turn it off so it doesnt overheat.

I took the two tubes off that are in the front and water is running through both of them. The same amount of water that is going through the earmuffs so what could cause the engine to overheat if water is going through the exhaust manifold and the block???

 

[Rocky_Road]

Re: Merc 3.0l Overheats

So I tightened up the alternator so there is no slack in the belt. It didnt help. Engine still gets up to 180 and I turn it off so it doesnt overheat.

I took the two tubes off that are in the front and water is running through both of them. The same amount of water that is going through the earmuffs so what could cause the engine to overheat if water is going through the exhaust manifold and the block???

180 is not an overheat...mine runs a 'click' over 175. All gauges are not created equal, and it would benefit you to get your hands on a temp 'gun' and check the thermostat housing at running temperature.

Do you have the temperature alarm installed in your 3.0? If the temperature switch has the red band, then it is the correct one and is set to sound the alarm just above 190 degrees.

 

[brsox88]

Re: Merc 3.0l Overheats

My guess is a tube was clogged or something. I reved it up a bit to put more water pressure through the hoses. It seems to be fine now running at 170 constant.

Only issue now which has been an issue for a little while but nothing serious quite yet is oil leak from what appears to be under the water pump? Its at the front of the engine but underneath. What could cause this? Same issue happened in the past on my fathers boat, is this engine prone for this?

 

[Don S]

Re: Merc 3.0l Overheats

Sounds to me like you need to check your impeller and the thermostat. The impeller should be replace every couple of years. How old is yours. With a raw water cooled engine, any number of things could clog, or stop a thermostat from working. They should be checked to on raw water cooled engines.

 

[brsox88]

Re: Merc 3.0l Overheats

I have yet to find a manual that describes pulling the out-drive off to replace the impeller. I know I could do it my self but I need something to follow. Even the videos on youtube didn't really help.

Anyone have ideas on this oil leak underneath the water pump? It leaks slow and its happened on both boats we have owned (both engines were the same)...is that engine known for this?

 

[Simoniz]

Re: Merc 3.0l Overheats

I have yet to find a manual that describes pulling the out-drive off to replace the impeller. I know I could do it my self but I need something to follow. Even the videos on youtube didn't really help.

Anyone have ideas on this oil leak underneath the water pump? It leaks slow and its happened on both boats we have owned (both engines were the same)...is that engine known for this?

Could be the oil seal on the front of the crankshaft or rust pinholes in the front timing cover.

 

[bobhol]

Re: Merc 3.0l Overheats

Here is a great link from the Bayliners Forum on how to change the impeller in an alpha 1 gen 2 http://www.baylinerownersclub.org/forum/showthread.php?t=33696&page=2 I did it right first time ...took about 2 hours...I wish I could find something like this for bellows and shift cable as that is my next project ...could someone please document the procedure so us wannabe mechanics can learn from it ...regards,Bob