6V92 running question - WOT

[ohiohatteras]

This is not a direct Hatteras related question....but you guys here have some extensive knowledge on DD engines, so that's why I'm asking for your help.....

Anyway....a buddy of mine just picked up a mid-nineties 43 Tiara open with DD 6V92's @ 550hp and 1050 hours. This is his first diesel engine boat and diesel anything for that matter. I have been trying to explain to him that he can't run thses DD's like he is used to running his 350 small block Chevy's or 225 Merc outboards! With the both boats, he would pin the throttles (WOT) as soon as he hit open water and leave them pinned the whole entire run. An entire run would consist of anywhere from 5 to 30 miles.....

Is there any information you guys can pass along or website/s you can direct me to so I can help him to prevent a pre-mature end of life for his DD's?

Thanks

 

[MikeP]

Generally, it's considered that these engines/boats run best at a few hundred RPM off WOT. A dock neighbor with a 58 Hat/92's says that's pretty much how he ran it until he couldn't afford the fuel any more. Now, like most of us, he reluctantly runs at/around hull speed. He says that a few years back he was either cruising at 18 Knots (pretty close to max speed on his boat) or at idle to maneuver in no-wake/marina areas.

30 Miles at WOT isn't a big deal with a clean cooling system; that's the only limitation - ensuring operating temp is OK. Obviously, with more load, engine life is reduced as it is with any engine. But the boats actually feel/handle a lot better on plane - that's what they were designed to do. If I could afford the fuel (and could keep the barnacles off the props/shafts), I'd be on plane all the time at cruise.

 

[Fanfare]

Here's the exact quote from the DD spec sheet for the 6V-92TA 550 bhp engines:
"MARINE MAXIMUM The marine maximum rating applies to high performance boats where speed is of primary importance and overal load factors are low. Normal or cruising RPM should be limited to 90% of rated engine RPM, and the use of full rated power should be limited to 10% (average) of operating time. This rating is normally reserved for privately-owned yachts in non-revenue applications with an average annual hour accumulation of 500 hours."

On March 15, 1993, I spoke with Mr. Al Kozal, VP Marine Sales of DD, to clarify the 10% full power limitation. He said that in a 30 day period it would be ok to run flat out for three days. My mechanic recommended no more than a few minutes a day to clear out the carbon and exercise the blower bypass valve which directs turbo air arond the blower and into the intakes. I have, in the past, run one hundred miles at full throttle when the engines were new and under warranty just to see if they would break. I do it about two minutes a month now.

At low speed, Mr. Kozal recommended running above 1400 rpm as this is where the turbos kick in. I find 1200 is about it for hull speed. So far I note no problems at the lower speed, with the occasional two minute burst.

 

[George]

If WOT is 2350 RPM, he should run at 2000 at cruise and 1900 if he wants the engines to last. That being said, I believe it's a very good practice that you make sure you get to WOT when starting out your day so that if you don't reach 2350 RPM, you know you have issues such as growth, fuel restriction, air restriction, or something else. I like to punch it up at the beginning of my journey for 3-5 minutes, check my WOT and then back down to in my case 1900 RPM (I have Cat C-12's) and if I have been at cruise, typically 2.5-3 hours each way from our canyons, I bring back to WOT for the last 5 minutes of the trip to clear out the bypass. This is common practice among avid offshore fisherman, as well a little ego if there is another boat near by I hope this is helpfull