4.3l Mercruiser - failed hose test see comments

[BestDay2023]

2005 Bayliner Bowrider with 4.3l Mercruiser

Just performed hose test. Water did not come out of transom but ended up in the bottom of the engine compartment. Water seems to be coming out of right side bottom.

Note: 2 things that may be of importance:
- Seller started boat without hose just to turn it over to show the engine starts. He had called his mechanic and said it would be ok for a few seconds tops. Engine started and immediately turned off.
- 5 blue water plugs and all hoses were securely in place, BUT there was one threaded nut that was not put back in. There seem to be 2 of those 1/2 - 3/4" inch square tall threaded nuts right in the middle front, but the one that did not get replaced during the first water test is right behind the left top hose clamp. Not sure that has anything to do with this.

Any direct experienced thoughts on this?

 

[dubs283]

Sounds like you're referencing the intake manifold drian plug located on the fwd side of intake just above the circ pump

If the engine is run with a sea water supply and the plug is not in place water would leak out the hole

Where down low on the motor did you see water leaking? Pictures help a lot

 

[BestDay2023]

Hello - thanks for your reply. I didn't see the water coming directly out but in general, while performing the hose test with muffs, the water never came out the transom but ended up in the engine compartment.

 

[dubs283]

while performing the hose test with muffs, the water never came out the transom but ended up in the engine compartment.

In that case there is a plug(s) not installed, hose(s) loose/not connected properly, or worse a pushed out casting plug or crack in the block or manifold(s)

You need to run the engine with a good water supply and look to exactly where the water is coming from

What does the engine oil look like?

 

[BestDay2023]

I just googled what you meant by a pushed out casting plug...and that is exactly what I found in the bottom beneath the engine. Praying for no major damage.

 

[BestDay2023]

And the engine oil looked good.

 

[BestDay2023]

4.3l Mercruiser
Boat failed hose test with muffs. No water came out of transom, but ended up on the floor of engine compartment. After a helpful comment from a Rear Admiral, I knew what had gone on. I've read on a few forums about this. Does this mean that the engine is toast? Odds that it might be ok?

 

[Scott Danforth]

if you have a pushed out core plug, 99.9999% chance the block is cracked.

 

[dubs283]

First step is to reinstall the casting plug. Then run the engine on muffs and check for any other leaks.

If no leaks let the motor run to temp for a while and turn it off. Let the motor sit for an hour or so and restart it. Let run for a bit and monitor oil level quality. If the engine oil is milky/overfull youve got a cracked block or intake manifold.

You could also pressure test the cooling system once the plug is back in. That'll show you if the cooling system is sound

 

[Scott06]

I just googled what you meant by a pushed out casting plug...and that is exactly what I found in the bottom beneath the engine. Praying for no major damage.

If that is what you saw it is evidence of freeze damage from incorrect winterization. If buying it I would assume the engine is cracked and pay appropriately, like price makes sense if you have to buy a new engine.

Similar thing happened to my neighbor years back got to winterizing too late had a core plug pushed out, took a few weeks of using it next spring for the cracks in lifter valley to open up and start pushing water into the oil.