1989 Mercruiser 2.5L 120HP motor overheating trouble shooting

[liusigou]

My boat cylinder pressure are down in recently years. now only 120,100,100,80. But it run great about 30 Mile at the beginning in the water and later it slow down in the end about 8 mile per hour. But The second day it recovers. Could somebody help me to do the trouble shooting?

1) I will check the impeller
2)I will do some flush with STAR BRITE Marine Descaling Fluid Concentrate.

Thank you

 

[Bondo]

My boat cylinder pressure are down in recently years. now only 120,100,100,80. But it run great about 30 Mile at the beginning in the water and later it slow down in the end about 8 mile per hour. But The second day it recovers. Could somebody help me to do the trouble shooting?

1) I will check the impeller
2)I will do some flush with STAR BRITE Marine Descaling Fluid Concentrate.

Thank you

Ayuh,....... Yer motor is a rebuildable core, not a runnable motor,....
Yer highest compression cylinder is barely passable,....

 

[liusigou]

it is running with hot water out after I Applied new impeller.

 

[liusigou]

it seems it cool down after I did a testing bypass outdrive

 

[matt167]

You either have a blown head gasket, or in need of a valve job or adjustment at least.

 

[airshot]

Pull the head, they are prone to warping and bad head gasket. Once head is off, check cylinders, if not great, time for a rebore. Often a head rebuild and straighten with a valve job will fix things, but a thorough inspection is needed. If you have overheated that head, for sure it will be warped.

 

[liusigou]

Is my 1989 Mercruiser 2.5L 's carburetor the same as 1996 mercruiser 3.0L's carburetor?

 

[matt167]

Chance you may be able to use it. But it’s not the same. It fits the manifold

 

[Scott06]

Is my 1989 Mercruiser 2.5L 's carburetor the same as 1996 mercruiser 3.0L's carburetor?

As mentioned Maybe jets could be different. Why not rebuild the one you have

 

[liusigou]

As mentioned Maybe jets could be different. Why not rebuild the one you have

it takes a lot of money to rebuild.

 

[matt167]

About $300 to have it done. Less than $50 if you can do it yourself…

They should be jetted close but the throttle linkage may be different

 

[liusigou]

About $300 to have it done. Less than $50 if you can do it yourself…

They should be jetted close but the throttle linkage may be different

rebuild my engine? big job for me. I am checking one boat with 130,125,120,120 PSI, seen my another thread.

 

[matt167]

rebuild my engine? big job for me. I am checking one boat with 130,125,120,120 PSI, seen my another thread.

I was talking carburetor… if you are wanting to swap a 1991+ engine, you’ll need the conversion coupler

 

[Scott06]

it takes a lot of money to rebuild.

A carb no it doesn’t get a kit from mikes carb parts. Otherwise yiu are throwing another unknown carb on it. stop throwing parts at it do it right do it once.

is this the engine that may have fuel system contamination?if that is not fixed doesn’t matter what carb you put on it it will get plugged with chit in no time

 

[liusigou]

Can anyone help me the trouble shotting of the overheat of my motor?. For my understanding the water can be intaken and the water can flow out. But why is it so hot and cannot help the engine cool down?

 

[matt167]

If you have a blown head gasket, compression ends up in the water jackets. Compression creates bubbles which creates hot spots. That may be your problem

 

[liusigou]

Today two people were in my boat and it run very well. The full speed is 34mph when returning after 7 hours in the water.

 

[liusigou]

Do you prefer to hold antifreeze in the block or you like ti drain it out while doing winterization for Mercruiser 2.5 or 3.0 l Mercruiser motor?

 

[Scott06]

Do you prefer to hold antifreeze in the block or you like ti drain it out while doing winterization for Mercruiser 2.5 or 3.0 l Mercruiser motor?

If you ask this question of two people on there you will get three different answers.

For me just drain, probe the drains to make sure there is no sediment blocking draining

 

[airshot]

And I was a person that used regular antifreeze and left it in the block. Gonna bet neither one if us ever had a problem ! My reason was to slow down the progression of internal rust, did it work.....?????