8v92 opinions

[Bob Bradley]

A friend of mine is looking at a Buddy Davis 47 with a pair of 8v92 engines at around 710 hp. Aside from exceeding the 90% hp/displacement rule, does anyone have any opinions pro or con on these engines?

I believe that they are late 80's models, with about 2100 total hours, and were majored about 700 hours ago. I presume that having to do a major at 1400 is a function of the horsepower.

Any particular concerns to be aware of?
Bob

[Passages]

Pascoe's book (Mid Sized Power) states these engines were highly reliable to about 650 hp. 1400 hours between majors with the higher hp is probably right.

[Genesis]

I have no issue with them if they are in good shape.

GET AN ENGINE SURVEY.

Good motors, but like all high performance diesels, they suffer neglect poorly. 92-series engines are particularly vulnerable to overheats due to being a wet liner design. I personally prefer that design over a dry-fit liner, but I've no issue with maintaining the cooling system properly....

[Fanfare]

Ten completely uneventful years on 6-92TAs (550hp), which replaced original 8-71Ns (350 hp), per Jack Hargrave's recommendation. For previous 30 years with the 8-71s, only problems were one broken fuel pump and one catastrophic lube line break at filter requiring rebuild (but still got me home once oil refilled!). Now, the Allison transmissions were far less reliable... Just change oil a lot (every 100 hrs), replace raw water impellers every two years, complete off-boat engine rebuild every 15 years or so when compression goes down. Detroits are infinitely rebuildable and there's nothing more reliable.

Jim Grove
Celebrating Fanfare's 40th year as a one-owner boat.

[Bob Bradley]

Thanks. I'll "remind" him about the maintenance requirements. Hull and engine survey under way this morning. I'll be running her for the sea trial next Tuesday if all goes well with the survey today. It looks to be a sweet deal, in the low 200's.

[Genesis]

Not a bad deal at all.

1400 hours is not unusual IF he ran them at the usual "200 off" advice. In fact, he did good going to 1400.

Those engines (indeed, any 92-series) are best run at 1900-1950 for reasonable life, and this assumes you can reach the full 2300 RPM. Be sure he's happy with the performance running there - if not, then those engines need to come out and be replaced with something that has more moxie, or he'll be doing short-time overhauls every few years.

The only way you should ever run at the "200 off" point, which is 2100, is if you can reach 2400 under full load!

[SKYCHENEY]

Fanfare,
what was the difference in performance going from 350hp to 550hp on a 50MY? Just curious. My ED has 465hp 6v92's.

[saltshaker]

Sounds like a great deal if the boat is in fair shape. They are hard to find under 300K. Most have 735HP 8v92TA's. Cruise is about 23-24kts @1950rpm w/o a tower. ER clearance is a bit low but you can fit low profile engines in there. I know the 10cyl MANNS fit in there. Very nice ride, although not as dry as you would think with all that bow flare.

Jack Sardina

[Fanfare]

I first overhauled Fanfare's 8-71s in 1980 (at age 15) because crankcase pressures were climbing and other stuff like hoses were randomly failing. Had them done at DD in Jacksonvile, FL. Prior to overhaul we could regularly do 18 kts or better. Engines and transmissions were pulled, all torn down, and rebuilt to 1980 specs. When replaced, we couldn't get on plane any more, even at 2300 rpm, and used twice as much fuel, at 13-14 kts. Just wern't getting over the hump. Tried everything to fix, in conjunction with DD--prop pitch, checked injectors, etc. No go. I finally concluded that the original engines had been hot-rodded a bit at the factory. Also, I had noticed that each time we went cruising we would arrive on board with three suitcases, but go home with only two--inevitably increasing weight. For the next 15 years we traveled mostly at hull speed. Around 1994 I began thinking about a second rebuild or a repower. I wrote Jack Hargrave, explaining the usage we made of Fanfare and our recent lack of speed. He recommended replacing the 8-71s with 6-92 TAs, since 8-92s wouldn't fit. In planning the repower the most important thing turned out to be retaining the 2 inch diameter shafts, which required going to Aquamet 22 shafting for the requisite strength. Transmissions were replaced with Twin Disc, which really made my life easier. On our sea trials with clean bottom, but full fuel and water and about 5 people we reached 23 kts at 2300 rpm, and other speeds proportionately--at 1700, 17 kts, etc. Now, when cruising, with full fuel, water, and a month's provisions we cruise at 1900 rpm and reach 16-17kts. As fuel burns off speed increases to 18. DD does not recommend slow running--less than 1600 rpm (where the turbos kick in), as this is said to put a glaze on the cylinder walls and increase oil consumption. However, when running the Intercoastal, where we are forced to run pretty near idle speed due to our huge wake on plane, I have not noticed this problem. Al in all, repowering has been a great benefit, both in speed and reliability. The 6-92s are great engines--you just can't run them at full throttle. That's not so bad, because while the engines are bigger the fuel tanks are not. Went from 40 gal/hr to around 64 gal/hr. And the speed is still there if a hurricane is behind me!

[SKYCHENEY]

Sorry, I didn't mean to hijack this thread, but Fanfare sure has an interesting story. I think it is great that he has owned his Hatt since new (for 40 years). It must be great to know everything about your boat and not be surprised by something that you found that a previous owner had done or not done. Congrats, Fanfare. I bet she is a real beauty and I'd love to take a tour someday if I ever run into you somewhere.

Sky Cheney
1985 53EDMY