Big turbos

[Tim Powell]

Had a chance to visit a 1990 45c this weekend with 692s i am use to seeing 2 turbos per engine. This 45c had only 1 turbo per engine. It was a a very large turbo and looked as if it had a oil line going to it maybee for cooling. The turdo was about the size of a dinner plate the ones i usually see it about the sizer of a bread and butter plate. I have ask a couple of guys without any good answers. Was it a add on or a factory extra or neather Tim

[nor'easter]

My 1995 6v92s and my current 1998s both are as you described.

[saltshaker]

Same here. Those sound like the wet turbos I had on my 6v92TA's. I think they started using them around '88. I've got 2 per engine on my boat.

[Fanfare]

My 6-92TAs (550hp, new in 1993, which I suppose means they are not so new any more) each have one large turbo, original from the factory. Best of all, the turbo and the exhaust manifolds are water cooled. This made my engine rooms run a lot cooler.

In all this time I have had no problems with these engines or their Twin Disc transmissions. No smoke, no oil burn. DD tried to talk me into the DDEC electronic controlled engines which gave about 30 more hp, that would be the first version of at least three versions, but I passed. In hindsight that was my best decision of the decade.

[captddis]

The "forward plan' engines have one wet turbo. The engine came out around late 87. It solved the problems of leaky exhaust joints, broken sweep pipes, got the airbox pressure up to where is needed to be and much reuced the risk of fire and also had by pass blowers. They also had boost coolers that solved the marginal cooling system on the TTA's.All in all a better longer lived engine.

For a number of years it was hard to sell a boat with the twin turbo 6V92's. Due to the above issues.

Some of the Hatts in 88 had Covington marinized single turbo 6v92 which was a TTA engine that Covington put a single wet turbo on and a bypass blower. Kind of an oddball.
For a very short time Covington used a Wet housing twin turbo 6v92 on the 53's.

[SKYCHENEY]

For a very short time Covington used a Wet housing twin turbo 6v92 on the 53's.

That must have been really late in the production of the 53. Mine is a 1985 and has the twin dry turbos. DLCameron's 53 has the same, although the data plate rates his at 475hp and mine at 465hp.

Here is a question for you, Dave. Is is possible and what would be involved to convert a twin dry turbo 6v92 to a twin wet turbo version? And would it be worthwhile to pursue if the engines were being overhauled anyway?

I am told that the shafts on the 53 can't handle much more HP, so if a conversion/upgrade was done, how much HP would be gained?

[Genesis]

I looked into doing the conversion on Gigabite -- 1895 Series II with the twin dry setup, twin 500HP 6v92 TAs. The conversion is to a single wet turbo (per engine), not twin wet.

It's expensive; in addition to the turbo you need to also rework the cooling system flows somewhat and the risers and exhaust collector needs to be replaced. The boost cooler needs to be added; I was told that if you didn't you'd DEFINITELY have overheating problems in Florida (warm) water -- I believe that as the stock system is notoriously close to the line as it stands. If you don't change the blowers you don't get all of the benefit so you want the bypass blowers with that installation, although if you have the stepped-up gearing on the blower (much cheaper than a new/reman blower!) you will get some of the benefit. I was told that many (maybe all?) of the wet turbo engines were also advanced timing which is another confounding factor in all of this.

I concluded it wasn't worth doing; collectors + pipes + turbo + boost cooler was well north of $10k/engine if I recall correctly, parts-only (doing all the work myself.) I might still have the quote on the parts somewhere but at this point it's more than 5 years old and thus likely worthless as prices sure haven't gone down on fabrication and parts.

[Tim Powell]

Mine was the twin turbo. They were hot all the time as a matter of fact i have seen them cherry red. I have replaced them twice not all of them as i remember purchased all new ones and two of the new ones went south. Befor i would take a long trip i would rock the blades by hand if they were loose or rough sounding you would have problens soon. After replacing the two i finally found out how to replace them. You must disamble and oil the baraings or the little sleve bench spend first if not and you crank it dry you will have problems. (i learned this from Covington marine) I did this with the last two and as far as i know they are still running. Another sign was the black hase if it started eaven dusting a little, look out it was asking to be replaced. (they are not cheap new ones anyway)
I was asking because i have never seen the single ones before but from what every one says. It looks as if the change came about 1987 or 1988 thats news to me. I thought i was looking at a add on or a option but seems its standard. DD must have discovered as I that the twin turbos should have been sunk. DD probley used them because it sounded cool fast and high performance.
(692TA twin turbo 535 hp) a mouth full and maybee a marketing tool.

Tim









Tim

[Genesis]

The dry turbos REALLY don't like to be shut down hot. The oil in the bearing will cook if you do, then the damage starts and its progressive. Hot shutdowns should be considered an emergency-only procedure where you're willing to sacrifice the turbos if you do it.

I had to change two of them on Gigabite exactly once soon after I bought the boat; once replaced I never had trouble with them again. But I never shut down hot. When you come off plane (e.g. at a spot to fish) let the engines idle for a good 5 minutes or so before shutting them down -- if you have pyrometers wait until you see "idle and cold" exhaust temperatures (~250F) before you shut 'em off.

That and improper installation (not filling the bearing before you start up a new turbo) are responsible for most of the failures on the twin dry system, provided the exhaust remains properly supported and doesn't cause mechanical problems with exhaust leaks. There is a higher fire risk with the twin dry system too especially if the blankets get oil on them but in general the setup isn't that bad.