Diesel vs Atomic 4 noise

Emerald said:

As we go insulating our diesel engine compartments, remember that many diesels call for running their ventilation blowers (yeah, like the ones you run for 5 minutes on the A4 powered boats ) continuously while the engine is operating, as the diesel receives (by design) a significant cooling affect from ambient air.

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David - I'm not familiar with any sailboat diesels that require forced ventilation. I calculated that my M-25XP sucks in 37 cubic ft of outside air per minute while running at cruising speed. That should suck out the hot air pretty effectively.

What am I missing?

blowers...

Other than air cooled yanmars in some Panda gensets I dont think any diesels require forced ventilation. But having a good blower can decrease the engine box temperature and the reduction in intake air temperature alone can amount to substantial power gains. I have a formula somewhere that shows the percentage of power loss vs. intake air temp. My engine box is almost completely sealed and I have the blower forcing air into it, with a passive exhaust hose to vent out the heat. Having the blower pressurizing the compartment means the engine won't have to work any harder to breathe. I ducted the blower to force the cool air up to the intake first. Gettin off topic but heres an interesting article for all the engine geeks like me... http://www.bankspower.com/tech_coolair.cfm

Most of the newer diesels are high compression engines, which makes it very difficult to hand crank, if not darn right dangerous. Best option to start a diesel without DC power is to install a spring loaded starter. Lucas used to make these, although not for every engine size. It works by loading up the spring mechanism and then release the power with a trigger. It's all part of the starter unit.

Joe
S/V Imagine

Hi Loren, Tom,


Couple thoughts.


Loren, you're right on the same page I am. I am hoping to find something like a Yanmar 3GMF to replace the 2QM15. I am not really going to put the A4 in - it's going to hopefully finance buying a used diesel in need of a rebuild. I do like teasing people about putting the A4 in - it get's such a rise - OK, I'll try to be good now


Tom, I have to go looking for my source on running the blower to help cooling on the sailboat diesel. Unfortuneatly, I am not where my library of manuals is, so I'll have to get back on this one. It is very possible that the information I had come across is obsolete in today's modern world. I will gladly stand corrected if that is the case. I will try to post back shortly with more information regarding ambient cooling - even if it's just to say I can't find the original source.


An observation I will make is that if I don't run the blower while motoring, the water heater which shares the same space but is not plumbed with the engine, gets considerably warmer.


-David
Independence 31
Emerald

Blower Operation Rationale

The idea of running the engine compartment blower full time whilst operating the diesel has been discussed before (...here or on the one of the Ericson listservs, I am not sure).
Gist of it was that, in general, one does not do it to help or hurt the air supply for the engine, as it gulps in massive quantities, anyway. This presumes that you have a sufficient-volume air intake passage for your diesel in the first place.

Our local diesel mechanic YC member, who conducts classes through the complete rebuilding of a marine engine, advocates running the blower all the time to exhaust the hot air that: 1) collects in the upper portion of the engine compartment, and 2) is close to the alternator.
Note that this applies ONLY to diesel engines!

When our boat was constructed, the air intake was a passive hose to the top of one of the engine stringers, and the powered exhaust hose intake was right beside it.


After talking the situation over with our mechanic/teacher, I removed the "intake" hose -- there is ample square inches of air access to the stern lazeretto area where there is an outside ventilator on the starboard side of the stern combing. Then I put in new hose from the top of the engine compartment, through the "turbo blower" and thence to a ventilator on the port side of the aft combing. If you have ever seen an Olson 34, these are the stock ventilator locations.
At any rpm, a *noticeable* amount of hot air is ventilated by the blower. It actuall feels rather good on a cold day when sitting at the helm.

The blower is run for several minutes after shut down, as well.

Loren in PDX
Olson 34 Fresh Air

To follow up on my prior posting, I am not finding my original source of information on ambient cooling, but did come across this, which gives some good general guidelines on the ventilation requirements and target temperatures for marine diesels in general and some Yanmar information specifcally.


http://www.yanmarhelp.com/i_vent.htm


Bottom line would seem to be that when insulating the engine compartment for sound deadening (or not), pay attention to what is going on with ambient air temperatures, and ventilate as required.


-David
Independence 31
Emerald

Re sounds, I came close to buying a Grand Banks 36 (twin 120 lehman diesels) instead of the Ericson 32. The Ericson M25 diesel is much quieter underway than the trawler--which is always under power. At the same speed! Subjective of course, but for me sailboat diesel engine sound in well insulated 32-3 is just not a factor. I find it soothing. I grew up with Atomic 4s, sniffing for gas and running the blower five full minutes. It was the first and most serious safety briefing everytime we got onto the boat and I don't miss that concern at all.

DIESEL is the best.

I've a nanni diesel 2.60d , 15hp. in my e27

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Diesel noise.

Two years ago, I replaced the gasoline single in my San Juan 26 with a Volvo D1-13 Sail drive. The unit is incredibly compact and almost vibration free. Space is an issue in these smaller boats and these new units will give you much more living space. The unit is whisper quiet in the cockpit but I need more insulation below. There are two other benefits of a diesel. 1) Diesel doesn't have a tendency to blow up if you are not careful. You don't have to run a ventilation fan (Most noise in my cockpit). 20 I am not sure what the engine uses for fuel but the tank stays up there. It can't use more than 2 qts an hour at the most. The boat easily cruises at 6 knts and tops out at 7.2. Not bad for a 6000 lb 26 footer. The older diesels make a lot more noise and vibrate a lot more (eg. the 1987 Universal in my E 34. Bob Morrison Ghost and Terra Nova

Emerald said:

A final thought. I think the biggest plus for a diesel that has not been mentioned is it's ability to run without electricity. This has more appeal to me than any other aspect. I am more worried about being on an extended cruise and having an electrical problem e.g. something is left on, the battery switch was left on "both" and you wake up one morning to stone dead batteries. With the diesel, if you are set with a hand crank, you should be able to get it running, charge batteries etc. Another of my paranoid scenarios would be the lightning strike that blows out the electronics on the boat, but the little diesel might just still run and get me where I need to go....

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Interesting comment about the hand crank. I have a little Yanmar 1GM and the hand crank, but I can't start the thing with it for the life of me. Nor, based on my searches on line, can anyone else! (The engine starts quickly and easily otherwise.) Perhaps it's the light flywheel.... Maybe other diesel engines fare better with a hand crank. Oh, and I think your comments on the A4 are very good. While I'm not sure I'd repower a diesel with an A4 (since that would harm the resale value), I'd also think long and hard before repowering an A4 with a diesel. I don't think they are especially dangerous if well maintained. My boat has propane and that's at least as dangerous--again, if not well maintained.