marine diesels

[JDougherty]

i know in a truck a diesel should last 300k - 500k miles with out a major overhaul, but in a boat how many hours should it go without an overhaul?

 

[Greenleaf]

Jay would know. They use hours of operation. I have a school bus with a 1989 "B" original parts save the cylinder head and injectors, turbo. 10455 hours on the clock. Still use it all the time.



-S

 

[JLEONARD]

A marine B should last 10,000 hours. The problem with thr marine application however, is that "marine age" is more likely to take the engine out rather than the number of hours.

By that I mean corrosion from a bilge with salt water, making corrosion, raw water cooling pumps that fail from lack of maintenance, those kinds of things are far more likely to take the engine out than running time.

Of course being propped correctly is another factor that most folks and boat builders don't pay proper attention to resulting in an overloaded engine.

On a boat, the engine must reach rated rpm inALL conditions... but usually a manufacturer will set it up for max rpm with no gear aboard. Add a couple thousand pounds of gear, fishing tackle, ice, beer, food, etc, and now the engine wonw't make it's rpm. Now,even at rpm levels low in the cruising range, the engine will be overloaded... . if boats came with pyrometers, that would be another story. .

I repowered a boat with a Cummins B (270 hp) and installed a boost gage and pyro so I could properly monitor load. Even properly set up and with the correct loading I was running 875 F post turbo at the mid cruising rpms.

Sorry for the lengthy post and hope it helped answer your question.

Jay

 

[JDougherty]

thanks jleonard... awesome answer.



it sounds like you are pretty familiar with diesels in a boat, i have always been an outboard man adn finally looking for a bigger boat... . i want diesels.



is there any marine diesels that you would stay away from?



so a properly maintained 2000 hr motor still should plenty of life left in it?

 

[JLEONARD]

so a properly maintained 2000 hr motor still should plenty of life left in it

Yes it should.

Here's a website that you may enjoy... I do www.boatdiesel.com you don't have to be a member to read and post. The Cummins section is very active.



I repowered a boat 5 years ago with a Cummins 6bta 270 hp diamond performance series engine. I just sold it. It was a sweet running engine, but they have their quirks and areas that need attention like anything. If it's raw water aftercooled you will want to clean out the aftercooler and intake pipes. In boatdiesel you'll read about using the "Joy" and water method for that. The sea water pumps need attention and impeller changing to keep the cooling system in top condition. But other than that they are pretty tough and reliable as long as you push their ability. Make sure the engine(s) can reach more than their rated rpm at WOT with a fully loaded boat. For example mine was rated at 2600 rpm... I propped it to reach 2650 at WOT. That geve a little room for a dirty bottom, extra beer , etc.

Then top rated continuos operation was 2400 rpm... . my normal cruising rpm was around 2100... . this is very conservative and will make the engine last a long time. If you were to run at the edge, 2400, most of the time, longevity will be affected.

At 2100 I was running about 15 psi of boost and egt was around 800/825 POST turbo. (can't go pre turbo because the exhaust manifold is antifreeze cooled ) At WOT the engine would develop about 30 psi boost and egt would be 850/875 or so, right at the max. Engine temp would stay at 190/195.



As far as engines I'd stay away from... that's a tough question. Getting support for technical assistance and service parts is very important for any engine. Cummins has a huge network, that's why I chose to repower with a Cummins. Yanmar has a big network, so does Cat. Deere is a good engine, but there was no support in MY area (Connecticut). And the Perkins I replaced was an "ok" engine, but I couldn't get parts easily... that's why I ditched it.

Lots of both Cummins and Yanmar support in Tampa.



(Now all that said, I just bought a boat powered by a Ford/Lehman diesel...



Hope this helps. Good luck.

Jay