Replacing stainless exhaust risers on Hatteras 70 -1990

Exhaust risers rarely leak saltwater into an engine if they fail. Usually they leak externally. Boost coolers can be pressure tested. What gives you an indication that any of these parts are suspect?

I ran a 1988 75' Hatteras MY on a 5300NM trip in 2008. Neither the risers or any of the coolers were a concern for RPM Diesel (the local DD authorized dealer). We had no issues with any of that stuff. I cannot remember if the boost cooler typically leaks externally or internally when they go. But have never had an issue with one on all the boats Ive run and maintained over the years. I had one DD transmission cooler go bad and leak once.

On the engines, change oil and filter, all fuel filters, have a tune-up done on them (adjust rack,injectors, and valves), change raw water impellors, inspect coolant and heat exchangers (replace/clean) as needed, change zincs, clean air filters, belts if so equipped. Same for generators (if both gens are the same a spare raw water pump is a good idea). On the gears change fluid and clean/change filter. change shaft and rudder packing if so equipped.

Spare Parts- plenty of fuel filters both primary and secondary, raw water impellors, belts (if equipped with any), oil filters and enough oil to do at least 1 oil change plus oil for adding, 3 empty oil drain buckets, engine zincs, a spare fuel injector or two, hose clamps of all sizes, 4' pieces of wire bound wet exhaust hose all applicable sizes, fuses, light bulbs, bilge pumps, float switches, a good wiring kit, tools, filter wrenches, shaft and rudder packing if so equipped.

We did 5300 NM on 7500 gallons. The first leg was Ft. Laud to Beaufort, NC and we burned 750 gallons to go 550NM, this was all at 1000 rpms, and then 1950 rpms for 30mins every 6 hours. The next day I ran at cruise all day from Beaufort to Coinjock and burned 700 gallons to go about 140 NM, but there were 30 knot winds. Everything in the Great lakes was at 1000rpms/cruise every 6 hours for 30 mins. BUT, there were area's where we couldn't do 1000 rpms and did around 800 due to wake laws and such. It also included a lot of idling waiting for locks and such. We also ran a generator pretty much non-stop and anchored 3 out of 4 nights and it's fuel usage is included in that. At 1000 rpms we averaged 10 knots, at 800 rpms about 8 knots, at 1950 around 16.5 knots. This particular boat had an extension and at 1000 rpms fuel balance made a great deal in speed. If the balance got off by 50 gallons foward or aft, she'd slow down from 10.3 knots to 8.5 knots.

I had a boost cooler on a 16-92 fail under load and it allowed water to enter the cylinders. It bellowed black smoke and sounded horrible which warranted an immediate shut down. The engine then needed a full rebuild.