Looking at 56 Hat's 8V92's Problem??

[Danali Star]

We are looking to move aboard fulltime to a larger boat once all of our rental property in Melbourne, FL sells (which has slowed lately, very frustrating). We are currently on a 43ft Gulfstar trawler with twin 100hp Yanmars and burn a whopping 1.5gph total at 8 knots, and although it is great for spending Nov thru June in the Abacos, we feel it is too small to live on full time. We have ruled out many of the 58's Hats prior to 1985 due to either loss of side decks for the size main salon we prefer, or the smallish "feeling" main salon in the yachtfish (vs 18ft beams) to keep side decks. We are leaning heavily toward the Hatteras 56 motoryacht in order to pick up the 18+ft beam with side decks, as well as other features, mainly large sun room/aft deck, larger main salon open to helm, galley down, only the main stateroom is aft of engine rooms, (we like the 58 motoryacht 1985 and later for the same reasons, but they push the price envelope). We would love a cockpit, but that pushes us into 12 cylinders (61cmy etc), and I don't think I am prepared for that. Both the 56 and post 1985 58's seem to be powered with the 8V92's. I have read extensively on several forums, and the frequent comparison to a hand grenade with a loose pin is concerning with the 8V92's. I have zero experience with them. Right now it is my biggest concern.

We do not plan to need speed, we run at hull speed 99 percent of the time in our current trawler, and expect to do the same in whatever we move to next. Fuel consumption is certainly an issue, but perhaps not as much as potential rebuilds on a used boat. One particular 56 on Yachtworld, Party Hatt, claims to do around 20 gph at 12 knots at 1700 rpm. If that example is accurate, I wondered if fuel consumption could be cut and engine life extended with these engines similar to what a friend of mine did with his 8V71's on a 58 Yachtfish. He took off the turbos, downsized the injectors and gets slightly less than 1 gallon per mile, running at 10 knots. OR...the other argument often discussed, decreasing the prop pitch to accomplish similar results. This change won't make or break the decision but if it could be done with the added plus of an extended engine life between rebuilds, I would certainly do it. I would also certainly consider a repower if a more suitable power plant would make more sense, both to engine life and efficiency as I plan to have this boat at least 10+years. Relative to repower, I was concerned about the resale if I repowered for hull speed and efficiency as a potential problem if and when I decided to sell the boat. I thought it might be important to be able to put the turbos back on, original injectors, etc in case the potential buyer wanted the original engine built for more speed. Any and all suggestions and comments are welcome, as we will be making this important decision sooner or later, but we hope to be ready sooner rather than later. It would be great to hear from 56 owners about things they like and don't like about them. Not sure how many were made, but you don't find many for sale. You get a total of only 6 or 7 for sale on yachtworld, versus pages of 58 yachtfish, 58 motoryacht pre 1985, 58 cmy, etc. Is this a sign of people loving their 56's and simply holding onto them.

[Genesis]

Leave the enignes alone and run 1100-1200 RPM.

You'll get 0.7-1.0nmpg on fuel and still have the ability to get out of the way of weather and such if you need to (and are willing to burn the fuel.)

That's how I'd go at it. There's nothing wrong with the 8V92s provided they are not too tightly-wound. Many of them are, but its the idiot with his hand on the throttle that causes the problems, along with a "gotta get 1/2 knot more" nonsense that many owners play.

[Danali Star]

[QUOTE=Genesis;68567]Leave the enignes alone and run 1100-1200 RPM./QUOTE]


Thanks, Genesis......That is excellent news to my ears!!! Thanks for the reply. I had all sorts of dreadful visions going thru my head. Simplified to a T...........

[SKYCHENEY]

I run my 6v92's at about 1400rpm for slow cruise with the occassional shot up to 1950 for 15 minutes or so. They have over 3500 original hours and still seem to be going strong. I would not be affraid of any 92 series engine as long you know that the PO wasn't abusing them.

The problem is that the 92's were not holding up well when they were first introduced. This gave them a very poor reputation and cost GM a bunch of money, not to mention customer loyalty. We owned several of these in trucks and they did not last long (the green ones). Then DD came out with what they called the "silver series" (painted white). These had several improvements and probably every marine version out there has been upgraded to those specs by now.

[Passages]

Agree, the 1978 - 1982, 8-92's had some serious issues but these have been corrected by now.

I don't know about the hand grenade assessment. As long as the HP does not exceed CID, you should be able to expect a reasonable service life.

[chris piazza]

Ive got 8v92's in my 53C. Try and stay in a lower HP rated engines, mine are rated at 550hp, some are even down to 450hp. If you get the 750hp rated 92's as Genisis said these are wound to tight and are short lived. I think the key is a good maintenance program, 1100-1200rpm cruise for 1mpg with the occasional run up to 1950. Also if the boat you chose doesn't already have the Racor CCV'c installed on the 92's this should be your first project

Chris
Superior Nights 53C

[StratPlan61]

The US Army has thousands of 8V92s in their HEMETT 10T truck. It is a heavy duty 4 whl steer, 8 wheel drive workhorse, produced in a dozen configurations. These engines are rated at 450-500hp and enjoy a reliable reputation. As others have noted, prudent operation and a motor configured in a reasonable HP version will outlast most of us. I looked at several 56s before I bought my boat, the 8V92 motors would not be a concern to me.

[Danali Star]

Ive got 8v92's in my 53C. Try and stay in a lower HP rated engines, mine are rated at 550hp, some are even down to 450hp.

Chris
Superior Nights 53C

How do you determine how one is rated. That is, what determines the HP rating. If you are looking at an ad, is there anything that tells you how it is rated other than the "HP" block on Yachtworld where they fill in the blank.

[Brian Degulis]

"Leave the enignes alone and run 1100-1200 RPM"

Yep what Genisis sugested is exactly what I do with 1271TI in a 61MY and get around that kind of burn. I use a cetane booster in the fuel and always run it up a bit for at least a little while each day just to clear it out.

I wouldn't consider removing the turbos I'm pretty sure the TI engine is lower compression than a natural which means that if you needed to run hard your probably be running less eficiently due to incomplete burn.

If you want to consider doing anything with the props you would have to do increase pitch or diameter preferably diameter. That will load the engine closer to rated load at lower RPM but will also cause overload at some point before WOT depending on how much bigger you go. So in efect you will be de rating the engine to a lower HP and RPM. You can get a pretty substantial gain in economy this way (I did it with one of my past boats) but of course you got to balance that against the cost of props and the potential to have to change it back if you want to sell it.

Before I got our 61' lots of people told me that taking a boat that's designed to run well above hull speed and running at hull speed would result in poor preformance and sea keeping ability. I don't see that at all my boat runs very well at hull speed. Most so called trawlers are semi displacment anyway and I think the shear weight of a well built boats like these goes a long way.

Brian

[hattitude]

If you want to consider doing anything with the props you would have to do increase pitch or diameter preferably diameter. That will load the engine closer to rated load at lower RPM but will also cause overload at some point before WOT depending on how much bigger you go. So in efect you will be de rating the engine to a lower HP and RPM.

I'm no expert, but isn't this advice backwards? I thought to lower the load on an engine, you need to make it reach over max rpm (50 to 100) by decreasing pitch or diameter. I thought any engine that doesn't reach max rpm is overloaded throughout it's rpm band, not just at the top.......

Or did I read this wrong...?