Evidence of saltwater damage / Merc 350 Mag

[BeebopInPB]

2011 260 Sundeck w/ Merc 350

Brought motor into marina for engine guardian alarm — starboard exhaust manifold overheat. Digging into it, marina discovered evidence of saltwater damage to thermostat housing (rust). They’re replacing the housing, but my concern is the saltwater damage is worse than just this.

Questions:

1) what sort of rust damage should I really be worried about? Risers and exhaust manifolds are of course concerning, but any reason to think the block itself could be affected also?

2) Living in the Midwest, what sort of $$$ would I be looking at to find out? I’m not terribly excited about having a boat that has a problem that would eventually be hugely problematic, if I could nip it in the bud right now.

 

[BeebopInPB]

I should mention that the boat was on a trailer, but was used in brackish water for a few years by previous owner in northern Louisiana. Boat survey came back clean, owner had copious maintenance records with lots of regular maintenance done to it.

 

[Scott215]

I've heard of salt water small and big block going way over 1000 hours, I use salt away and flush after ever use. Does it work I don't know but makes me feel better, and I'm in salt water

 

[blaster]

If the manifolds and elbows/risers are original I would take a close look. Pull plugs and do a compression test. If the plugs look good I would start fresh with new manifolds and elbows/ risers then go boating.

 

[Golfman25]

As others have said. Start fresh. New risers and manifolds, thermostat and impeller. Also, if you can run Rydilime or similar thru block to descale. In fresh water you should have limited problems.

 

[BeebopInPB]

Thanks so much for the feedback. I don't want to make this the next guy's problem, so I suspect I'll probably go through with this over the winter (if not required sooner).

 

[BeebopInPB]

Followup Question:

Any idea of what we might be talking about, dollar-wise, to pull/replace manifolds and risers?

 

[Espos4]

A shop probably charges 4 hours labor plus parts. Also a good idea to replace spark plugs with the manifolds off as they are easily accessible.

Look up the parts on Nuwave marine or Michigan Motorz and figure $130-$180 per hour labor.

 

[BeebopInPB]

So aside from Risers/manifolds, thermostats and impeller, assuming there's no water leakage INTO the engine, are there any other places to be concerned about? can salt water develop enough rust to damage the galleries inside the block itself?

 

[blaster]

You should be good to go. Especially if you are in freshwater moving forward. Keep up with regular maintenance and everything should last a long time.