Yamaha F25 exhaust leak

[Bronlonius]

2003 yamaha F25 4 stroke. This outboard came on a boat I bought about a year ago. The symptom was the exhaust got louder as the engine warmed up. As you can see from the pictures, the leak is definitely coming from the oil pan gasket (exhaust manifold also passes through this same gasket). The gasket itself is intact, and all of the bolts felt tight. The oil was sooty. The large passage in one of my pictures is also full of soot, I don't think exhaust is supposed to be there (looks like a water passage to m). Is it possible that someone simply torqued this improperly, or is there something bigger I'm missing. I pulled the powerhead off, and I don't see any evidence of cracks on any of these parts. The model number of the motor says it is remote steer, however it is actually a tiller. So it's possible it was pieced together with parts from more than one F25. I can't find anything on the internet about other people having this problem, so I'm assuming it has to be caused by someone else messing with it and not following the torque specs in the manual. Just want to check and see if anyone else has run into this before I spend $100 on gaskets.

 

[Bronlonius]

One other question, what is the purpose of the hole in the side of the exhaust manifold, and the larger hole on the side of the oil pan casting? They look like they were intentionally made this way. I don't see any reference to them in the service manual, so I am assuming they are supposed to be there.

 

[Bronlonius]

Bump... Anyone have any input?

 

[robert graham]

Give this some time and hopefully Rodbolt will reply.....

 

[Bronlonius]

Thanks Robert,

I have the gaskets now, so if I don't hear anything soon, I'm just going to put it back together and hope it solves the problem. I think someone might have taken it apart and re-used the old gaskets, or simply didn't torque it properly. I will post my (hopefully quieter) results once it's working again.

 

[99yam40]

Make sure the surfaces did not get damaged with the exhaust blowing thru.
Gaskets have to have a surface to contact to work

 

[Bronlonius]

Well, it's back together. The gasket surfaces were all nice and smooth, no sign of warpage or corrosion, so I'm assuming this problem was caused by someone re-using old gaskets(they are crushable metal like a head gasket, so can't be re-used), or not torquing correctly. The engine is quieter, the obnoxious exhaust tick is gone, but it is still not as quiet as I had hoped. My friend's 2006 yamaha 75hp 4-stroke is much quieter. But, I have not run it on the lake yet, just in a tank. Maybe it will seem quieter when the boat is moving.

After doing some more research, it seems the 30HP and up have a muffler, the F25 does not. While not cost effective, I wonder if a leg/lower unit and exhaust setup from a 30HP will fit on a 25? From the pictures, it looks like the 30HP leg is thicker, to accommodate the muffler.