5,7 Mercruiser overheats

[Ostsideend]

Re: 5,7 Mercruiser overheats

Dear Oliver,
A lesson i took last 3 years is never to disassemble anything unless you cover any possible test to get more certain.Many things e.g a gas pump may work fine and after disasembly may leak.The test i did ,revealed my problem at dock ,not under load.I sugest you did it using a big barel to sinkthe outdrive (on mufs you ''ll certainly find bubbles ).Good luck!

Hi sarantis,
tomorrow i will put 1 bar of pressure onto the internal cooling circuit. With an medical endoscope i will try to see via #7 spark plug bore where the leaking comes from. If it is not visible, i will disassemble and check for mirco cracks with a special spray or other hints for leaking reasons.

Press me the thumbs as we say in germany for luck. Hope to find a failed gasket only.

With best regards
Oliver

 

[sarantis]

Re: 5,7 Mercruiser overheats

ok good luck but first i hope you did a compression test to your exhaust manifolds.The other days somebody gave a test for them using acetone if you don't have an air compressor,now this test is at the top(for adults only).
Anyway i believe the most possible is to go for resurfacing the heads and replace the head gaskets but first check your exhaust manifolds.

 

[Ostsideend]

Re: 5,7 Mercruiser overheats

Had the exhaust off, they are relaively pritty and fine. Took heads off. 5 of 8 Zylinders got seginificant "friction" marks. Block seems to be cracked. Check it with magna flux or similar later, just to understand.
Whatever. Again new short block....
Is there any problems known by using a 1/2 cycle heat ecxanger system for 5,7 merc. with alpha one G2 ?
What was first chicken or egg? Heat or a crack in the block?
best regards
Oliver

 

[Ostsideend]

Re: 5,7 Mercruiser overheats

Block is cracked.

All 3 crack lines in different cylinders goes horizontal. Just opposite a cooling channel. Probably there are more cracks but i didn't check.

Thin red line above the red section is one of the cracks.



I did hear the buzzer noise of the warning once only. I directely slowed down. I have used the motor for another 80 hours since then beeing careful but on higher temperatur than normal.

The check set, from the left:
1st cleaner
2nd red base colour
3rd activator



The new fully assembled longblock does suck water from the outlet (raiser) like it's free of charge. (reversion) I did read a lot yesterday about "reversion" but i found only thats a little of water going back.
In my case its a glas of water after some minutes in idle. By stopping it floods the cylinder via the valve seat.

I changed the complete exhaust assy to new ones, same thing, i changed the comlete assy from a buddys boat to a different exhaust maker, same thing????

Who will test my nervs? What the fu... is going on?? Is this the problem i already had on the pre engine?

Can anyone help me out?

With best regards
Oliver

 

[Ostsideend]

Re: 5,7 Mercruiser overheats

The water reversion stopped when disconnecting the seakamp heat exchanger without any other changes. Made a raw water cooled system only.

Can anyone try to give an explaination? Its way out of my understanding.

Thanks a lot.
Oliver

 

[Ostsideend]

Re: 5,7 Mercruiser overheats

It did not stop. Made a "final" test by today. New long block motor is sitting on a wooden frame. Garden house attached. More than 1 Meter exhaust house attached each side. GM cast iron bowtie is mounted. All raw water cooled only. After ideling for 3 minutes the elbows inner diameter have been fully wet and a significant amount of water was in the exhaust manifold. Again changed to an original mercruiser exhaust manifold, same thing. Did run the motor with higher rpm before shut off, same thing.

Is there anything stupid what i dont recognize?

Oliver

 

[xrayjoemd]

Re: 5,7 Mercruiser overheats

Don S,

Sorry for replying in this thread, but I don't see where i can start a thread or ask a question. I have a 2000 SeaRay with a Merc Alpha One that only has 120 hrs. on it. I noticed that water wasn't flowing out the prop as usual while on the rubber flush thingy placed over the intakes on the lower unit. I pulled the lower unit, the propeller etc. were like new. I should of shoved the hose into upper unit to check water flow, but I didn't think of this and re-assembled already. Now I see that there is very little or no water coming out of hoses at the thermostat housing with the engine running, even at higher rpms. When I attach the hose to my engine flush kit, water comes out the prop just fine. It would seem that I have some obstruction in the upper outdrive? I guess I'll have to pull off the lower unit again and see what I can find. The boat was unused a few years, killing my fuel pump that I just replaced it ($260, ouch) only to discover this problem too. There were no problems the last time I ran it a couple years ago. I'm thinking of testing it in the river to see what happens as I doubt I will find anything in the lower unit, it seemed clean. Perhaps this will help force water through. I appreciate any advice.

 

[Don S]

Re: 5,7 Mercruiser overheats

Just above the Adults Only sticky at the top of this forum is a button that looks like this.

 

[meesh]

Re: 5,7 Mercruiser overheats

To post a thread, Go to the top & click on thread tools. A box will drop down at wich point you will want to click on post a thread. It's that easy.

 

[meesh]

Re: 5,7 Mercruiser overheats

Oops, sorry I had you clicking on the wrong thing. Don is right as always.

 

[meesh]

Re: 5,7 Mercruiser overheats

Can also be done by clicking on forum tools, that's what I was thinking of.

 

[xrayjoemd]

Re: 5,7 Mercruiser overheats

Perhaps my interface is different or restricted, as I don't have the Adults only Sticky, Create New Post, or "thread tools". My options are:
User CP FAQ Members List Calendar New Posts Search and Quick Links.

 

[xrayjoemd]

Re: 5,7 Mercruiser overheats

I found "thread tools" but there is no option to post there.

 

[Ostsideend]

Re: 5,7 Mercruiser overheats

I found "thread tools" but there is no option to post there.

You can use this thread... there is no help possible for me out there.

Best regards
Oliver