Omc 3.0 exhaust out of the drain on the exhaust manifold

[Zseasprite]

New to marine engines, but not others. Bought this boat cheap and it has a slight miss. Plugs look good and all of the ignition is good. I had it running with the muffins on and decided to check the drain on the exhaust manifold and I got water and exhaust. So manifold or head gasket. What's common on this engine.

 

[HT32BSX115]

New to marine engines, but not others. Bought this boat cheap and it has a slight miss. Plugs look good and all of the ignition is good. I had it running with the muffins on and decided to check the drain on the exhaust manifold and I got water and exhaust. So manifold or head gasket. What's common on this engine.

Howdy,

Welcome aboard!

Well, if you opened the manifold drain and got water, it's pretty normal You should get water. (it's a jacketed manifold. The drain is actually there for draining during winterization.

On the other hand, there should never be any water in the actual exhaust port, but the only way to check that would be to remove the riser and manifold and look for evidence of water (rust etc)

A "slight" miss is hard to diagnose but it's usually ignition or carburetion or a vacuum leak etc. (just like any automotive engine)

Is it only missing at idle or medium throttle? Have you run it on the lake at full throttle?

regards,

Rick

 

[Zseasprite]

It misses more with acceleration. What I got out of the drain was water and some puffing like exhaust. I also had water in the oil, but I knew it had been settling for about 2 years.

I think I will start with a compression/leak down test.

 

[HT32BSX115]

It misses more with acceleration. What I got out of the drain was water and some puffing like exhaust. I also had water in the oil, but I knew it had been settling for about 2 years.

I think I will start with a compression/leak down test.

If you have water in the oil, you need to do a cooling system pressure test. If it will not hold pressure, you have either a cracked block, head or a leaking head gasket (in that order of occurrence)

 

[Scott Danforth]

could also have a cracked exhaust manifold or riser or a bad riser gasket

 

[Zseasprite]

Ordered a head gasket set going to pull the top end down and inspect. At the least I will know what I'm working with.

 

[HT32BSX115]

Ordered a head gasket set going to pull the top end down and inspect. At the least I will know what I'm working with.

Head gasket leaks are not as common as cracked blocks.....

You should pressure check the block and heads before pulling the head to rule that out. You cannot easily pressure check a block with the head off so do that first.

Also, you can pressure check the manifold by bolting a plate between the riser and manifold with 2 home made gaskets above and below the blocking plate Then connect an air compressor to the manifold cooling water hose connections using a gage and a valve.

The manifold and cooling system should hold 15-20 psi for an hour or more.

If the block or head or manifold is cracked, you will hear it. if the head gasket is leaking, you can hear it in either the intake or exhaust depending on which valve is open. If the block is cracked, you can usually hear it in the oil fill port, and If cracked on the outside of the block (under the manifold) soapy water on the cracked area will produce bubbles.

 

[Zseasprite]

Thanks for the input. I am not really familiar with this motor so I'll ask this question What is the best way to pressure test the block and head? I assume (yes I know the adage ) I would just drain the water jacket and then use some type of adapter to add and measure air pressure. I can't exactly put my pump on the radiator and test it like I've been taught since, there is no radiator.

 

[Bondo]

I can't exactly put my pump on the radiator and test it like I've been taught since, there is no radiator.

Ayuh,.... Welcome Aboard,..... Take the radiator adapter off yer pump, 'n adapt it to 1/4" pipe for the block drain, or 1/2" pipe for a t-stat port, or to 1 of the rubber hoses involved, usin' whatever it takes,....

 

[Zseasprite]

Ok for the latest easter eggs. Seems the stringer 400 impeller is not pumping water so I will get that coming. The motor runs great without water until it gets too hot, and no water in the oil lol. Anyway picked up a derelict boat with what appears to be a good mercuiser 140 in it. I'm going to swap it in and see how that goes. Any thing I should know before the swap. Going on vacation next week so looks like it won't see water until mid Aug. if I'm lucky.

 

[bruceb58]

Good luck swapping the transom assembly if that was your plan. The stringer hole is too big.

 

[kenny nunez]

You can use the engine by swapping the drive coupling, the OMC manifold also will have to be used over as the Mercrusier riser will be "clocked" differently and the throttle controls are opposite. Of course the OMC wiring harness will have to be re used. Also re use the OMC front mount.

 

[Zseasprite]

Good luck swapping the transom assembly if that was your plan. The stringer hole is too big.

I figured I'd just glass over the hole and start over ( sarcasm ) No I am keeping the stringer 400. Just using the base engine and swapping accessories. Thanks for the couple advice I had wondered about that.

 

[bruceb58]

I figured I'd just glass over the hole and start over ( sarcasm ) No I am keeping the stringer 400. Just using the base engine and swapping accessories. Thanks for the couple advice I had wondered about that.

People do that sort of thing. Gets rid of the stringer drive once and for all!

 

[Zseasprite]

People do that sort of thing. Gets rid of the stringer drive once and for all!

I had the thought for a brief moment, but the stringer drive seems good just a pita to work on compared to some.

 

[Zseasprite]

Update: All parts received and about to dive in. Sterndrive impeller replacement and engine swap.