Issues with long idling Detroit's?

[RyanB]

Been looking at larger boats recently, all of which have diesels. I'll be completely honest, I'm not a diesel guy at all, yet. I've read a ton of post, reviews, articles etc. but still have questions.

The #1 question I cant seem to find an answer on is dead idling diesels for long periods of time, while in gear.

Our boating is 60/40 fishing and cruising. While fishing for salmon (Great Lakes), we have to run dead slow around 2-2.5 mph. Unless its really snotty out, I accomplish this by killing one engine and basically idling the other motor to slow the boat down. I'll throw out a trolling bag 90% of the time, which allows me to gain a few RPM's but the running engine is still around 700 rpm(ish). Current motors are 350 Crusader Big Blocks, they seem to love idling all day. 95% of the salmon charters doing the same thing, run big block crusaders. Very few run diesels, so I don't have an audience to ask locally.

Will this kill the older diesels? I've read about washing cylinders but still not 100% I get what it entails. If this is a major issue with one motor vs. another, I'd like to scratch it off the list.

The boats I'm looking at have the below engines:
J&T6-71T 325hp (Seems too low of HP, but that's what I'm being told) - in 42C
Cat 3208 375 HP - in 38C Series II
Cummins 450C - in 43C
8v92 650HP - in 46C

 

[SKYCHENEY]

You can do it. Idle while fishing but run them up on your way back in to clean them out.

 

[cww]

This is only an issue if you never plane the boat and then wonder why the engines are smoking. Wet-stacking is just a quirk of the cylinder wall intake grid design, it doesn't hurt anything and is only a problem if you only ever putt around. Just run them up for 15 minutes and it goes away.

 

[luckydave215]

If the engines are turbos excessive idling/slow running will carbon up the turbos until they eventually jam, then it turbo rebuild time.
Guess how I know?

 

[SKYCHENEY]

If the engines are turbos excessive idling/slow running will carbon up the turbos until they eventually jam, then it turbo rebuild time.
Guess how I know?

Not if you run them hard. It will clean them out. You just have to do it every time you're out.

 

[RyanB]

Not if you run them hard. It will clean them out. You just have to do it every time you're out.

That's pretty much exactly how an average day would run. 6-8 hrs of idling but would always run back to port on plane, for several miles.