Running Engine Blowers

I've always thought of diesels as big air pumps and that an intake blower was not needed for regular operation, but only to cool down the ER after shutdown. Add to that my fear of salt in the works, and I'd take an awful persuasive argument for me to believe that running them while operating was wise.

I only run them for cool down and only then, when I have to do maintenance for the next day.

It depends on the boat (diesel boats). If the engine room stays salt free with them on at cruise, I run them all of the time when the motors are running to keep engine room temps lower, which helps keep interior temps lower also. If it brings salt in while running with the blowers on, I'll leave them off and only run them when doing non-planing speeds to keep the engine room cooler and after shutdown to cool off the engine room.

Delta T is standard equipment on new Vikings. When I was working for Viking one side pulled air in and the other pushed it out. I thought they needed to be reverse-able so that if you had a beam sea on one side you could push air out that side while running.

Cabo also used Delta T

Surely it makes no difference to the salt getting in the ER if you have a fan that blows into the space or one that sucks out and the air is drawn by this.

On the boats I am most familiar with we run 2 supply and 2 exhaust fans, these have an automatic mode when they are controlled by a pressure switch so there is always a slight positive pressure.

One of them is also reversible and fed by the EDG to be used if CO2 has been released in the E.R. to help ventilate it prior to re entry.

Both my ER blowers fill the ER, not pull from.

I seriously doubt the architects of these boats would put in these huge fans if they were not meant to be run while underway. We have two huge delta t fans connected to freq. drives. Is there not some engine benefit to having them run while under way?

Well, the cooler the engines intake air, the denser it is and the more power you derive from it. Would 3-5F make enough of a difference to notice, who knows. You never know why manufacturers install what they install. It could be to cool the engine room as quick as possible after the boat is docked in case you need to work on it.

I managed a 63' Hatteras MY, around a 2003 a long time ago and it had 2 air conditioners in the engine room. The owner had the factory install them in the build because he liked to do his own maintanence and tinker in there and wanted it cool, they weren't for use while the motors were running.

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Approximate consumption of combustion air for a diesel engine is 0.1 m3 of air/min/brake kW (2.5 ft3 of air/min/bhp) produced.

Cat specifies both requirements for air cooling and air combustion. If a pair of c32 is trying to achieve 3200 hp by burning 200gph, it will need a certain amount of air to achieve that design goal or the fuel won't be effectively turned into Hp as designed. Perhaps if you are going slow the need for increased air flow is not needed. But this is why builders are spec'ng $20,000 engine room fans. Not just for cooling

https://marine.cat.com/cda/files/4387976/7/LEBW4971-05 (1).pdf

Enjoy.

It depends. If the engine room air intakes are large enough then even C32 engines can get the air they need without any sort of engine room blower. One way is to run at cruise and see if there is any suction/vaccuum on the engine room door when you open it.

How do you keep the engine room temperature down when underway if the only air being introduced to the engine room is that for combustion?

It's for both combustion and cooling.