Mecruiser 3.0L Hissing Sound

[SpringVelocity]

Well report back....I got some great help and advise from a lot of people..I thought I would post it in here.... We seem to have some weird pre-detention problem...So long story short head gasket was replaced and it blew again .... This time it also took out the manifold gasket...

Just wondering if any of you with inboards had an experiences with this...Its pointing to something electrical that is throwing timing off... Any one have any ideas timing and mixture are bang on...Block is true and head has been machined and true... Compression was good before it blew..

Motor is a Mercruiser 3.0 LX/Alpha one leg...

Its a weird one.

 

[runamuk]

A vacuum gauge will let you know if your timing is out. Timing should have been set when you started your engine up . If it is the original distributor there should be nothing extra special about setting it up ie. total advance etc. If it is so advanced and pinging enough to blow a head gasket right away you would have heard it ping and it would have been very hard starting hot, almost like a bad battery. I have seen another scenario with marine engines that took out new head gaskets and that was corroded threads in the block that the head bolts thread into. This gives a false torque reading on the bolts. When you replace your head gasket chase all the threads with a tap and coat it with some engine oil. Then rub some engine oil on your head bolt threads as well as a small amount under the head of the bolt that contacts the head... Hope this helps

 

[trendsetter]

Did the head gasket blow near the same cylinder as last time? Is there any chance that you have water in your fuel?

 

[trendsetter]

This might be some help: http://www.boatfix.com/merc/Bullet/98/98_14.pdf

 

[SpringVelocity]

This might be some help: http://www.boatfix.com/merc/Bullet/98/98_14.pdf

Yah I saw that one it is 94-95 vintage though....

 

[Filletandrelease]

Well report back....I got some great help and advise from a lot of people..I thought I would post it in here.... We seem to have some weird pre-detention problem...So long story short head gasket was replaced and it blew again .... This time it also took out the manifold gasket...

Just wondering if any of you with inboards had an experiences with this...Its pointing to something electrical that is throwing timing off... Any one have any ideas timing and mixture are bang on...Block is true and head has been machined and true... Compression was good before it blew..

Motor is a Mercruiser 3.0 LX/Alpha one leg...

Its a weird one.

Highly unlikely detonation would take out a head gasket so quickly. And not sure what you mean about taking out a manifold gasket. There is nothing common there. Have you pulled it apart yet? The damage to the gasket should tell you the story. I would bet it was not torqued properly if your surfaces are indeed true.

 

[SpringVelocity]

It is we pulled it apart and that info on pre-detenation is coming from mechanic and shop that planed the head.....You can see it on the gasket...

 

[trophy fisher]

Does it have a mechanical distributor or electronic ignition? Where the valves and guides done when the head was machined?

 

[Hourstonglassic]

Was it set in base timing? I believe you jump the two white wires coming off the distributor together and ground out the white wire with green tracer up top. I haven't done one in awhile so u might want to double check that procedure .timing is usually 1 or 2 degrees on those things. And what year is this motor, those tks modules on the newer motors like
To hiss

 

[Filletandrelease]

It is we pulled it apart and that info on pre-detenation is coming from mechanic and shop that planed the head.....You can see it on the gasket...

With all due respect you are not going to see detonation on a head gasket. What does he actually see? Severe detonation will show as piston material transfer on the spark plugs. The plugs would be glazed and the porcelain will have spots on it. If this was happening you would know long before any damage by the Ping noise and poor performance. Yes timing is very critical but it will not cause a head gasket failure this quick. What do the plugs look like? Where exactly did the gasket blow? Between cylinders or cylinder to coolant jacket?

 

[profisher]

I don't think it has anything to do with timing, as others have said you would hear severe pinging that you couldn't not hear. I asked you at the show if the mating surfaces had been planed and you indicated they had so really all that is left if improper torquing of the head bolts or the wrong head gasket. I would do as been suggested and make sure your threads in the block are clean by re tapping them until the head bolts can be turned in by hand. Then you know that when you torque them they are at the proper number. Try turning the bolts in by hand prior to doing this, I,ll bet you can't.

 

[Filletandrelease]

I don't think it has anything to do with timing, as others have said you would hear severe pinging that you couldn't not hear. I asked you at the show if the mating surfaces had been planed and you indicated they had so really all that is left if improper torquing of the head bolts or the wrong head gasket. I would do as been suggested and make sure your threads in the block are clean by re tapping them until the head bolts can be turned in by hand. Then you know that when you torque them they are at the proper number. Try turning the bolts in by hand prior to doing this, I,ll bet you can't.

Agreed. While on the topic of head bolts, you need to check the actual bolt holes. If they are open to the water jacket you need to use a thread sealant. If any of the holes actually bottom out it is impertive there is no fluid in the hole. This will cause hydrauling when trying to torque the bolt. As if you need anymore bad news, many head bolts since the mid 90's are a torque to yield type bolt and are not reusable. They will not torque up a 2nd time.

 

[SpringVelocity]

Thanks for all this guys this is why I like this forum for things like this..Good points....

 

[SpringVelocity]

So update on this so I can pass on info..This was an overheat issue, and now explains why we had a head gasket blow twice.. This week I am replacing impeller and thermostat...

What has been happening when the engine is cold the thermostat appears to be sticking.. Basically it overheats initially on plane... It can steadily climb over 200 matter of seconds .... If I say just run for a minutes at 2000RPM not on plane, and then go UP TO 3500 rpm its fine... The thermostat kicks in. A ran a test set of bunch of sea trials and its definitely only happening when engine is cold.. Once its gets going its 170 all day long.. But the takeaway here is always watch temp gauge...Outboard or inboard... Its possibly a 12.00 parts cost me big bucks by not paying attention. I will look at impeller when I take it out this week.. But at least we found the demon so to speak.

Next one I will be doing it taking Wolf's advice and putting dry fit. manifolds/risers on..More I read the more I like them... I have to admit I am getting more comfortable with this motor now but it has been a learning experience for sure... Can't say it was any worse than my outboard..But definitely see issue with this motor as I think it sat around a lot.... Motors that sit break. They need to be run.