Should I be concerned?

[Essayons]

Happy engine, happy boater

I also changed the oil/filter, spark plugs, and spark plug wires. Easy without the manifolds in.

for anyone wanting to attempt this, it’s straight forward if you have any mechanical aptitude. I would also recommend using a torque wrench to tightening the bolts, rather than feel. I torqued them to 25 ft-lbs, let the engine warm up and retorqued. I think if you overtorque the manifold bolts, you make risk leakage. That’s my opinion based on the bolt pattern used. The middle two ports will have no issue, but the end ports only have one bolt at each port. Over-torquing MAY cause uneven pressure on the gasket.

great advice on keeping a log.

 

[Essayons]

Just tieing off all the loose ends. These are pics of the manifold and risers I replaced. I’m not sure, but I think I could have gotten another 5-10 years out of the old ones

 

[Espos4]

By the looks of those pictures, it’s a miracle that you avoided serious engine issues.

 

[Thornton69]

It looks like there are a couple large piece of the risers missing? If you didn't find them, they are likely sitting at the bottom of the Y pipe or in the transom/bellhousing assembly. If that is the case, it is possible you will have heating/performance issues at higher rpm's.