Hatteras 58' LRC are 4-71s sufficient

From my research, I've noted that the 58' LRC usually is equipped with twin 4-71s rated at 175hp. Some, however, come with 6-71s 225hp. The vessel weighs 90,000 lbs.

For normal, relatively slow speed 7-8 kts or so, cruising, would the 4-71 be sufficient leaving an adequate margin if needing to go a bit faster to avoid storms etc., or would I find them wanting in the hp department. I am leaning towards the 4-71s if for no other reason that for a in-place overhaul, running rack, adjusting valves etc., its 1/3 less parts, adjustment etc.

The 4-71 should be fine for that boat. Even with the 6-71, full power might mean just one kt of extra speed. Not really worth it for the bigger engines.

At 175hp is that a turbo 4-71? Probably...

We looked at a 58 LRC that had 471s in it. The 671 may give a bit more but remember this is a displacement hull so you aren’t going to get much more speed. The boat we looked at didn’t have turbos. I believe the vast majority had 471Ns in them rather than the 671s. It had a speed vs fuel usage chart that I will include here fyi.

Comodave said:

We looked at a 58 LRC that had 471s in it. The 671 may give a bit more but remember this is a displacement hull so you aren’t going to get much more speed. The boat we looked at didn’t have turbos. I believe the vast majority had 471Ns in them rather than the 671s. It had a speed vs fuel usage chart that I will include here fyi.

Click to expand...

Thank you VERY much. Most helpful.

Open-d said:

Thank you VERY much. Most helpful.

Click to expand...

No problem, I am only here to serve... (or not)!

Hopefully Juliet15 will be along shortly - he looked at a bunch of 58LRCs and bought a very nice example.

I have 4-71s in my 58LRC. They can push me along at 9.6 knots, which is the theoretical hull speed. They're amazing.

Mine are non-turbos (4-71N).

I did look at a bunch of 58LRCs until I bot mine in 2019. If you want to talk feel free to shoot me an email. neildeb2@aol

Te usual ROT on 71 series DD is 20 to 30 HP per cylinder is a "forever" load.

Juliet 15 said:

I have 4-71s in my 58LRC. They can push me along at 9.6 knots, which is the theoretical hull speed. They're amazing.

Mine are non-turbos (4-71N).

I did look at a bunch of 58LRCs until I bot mine in 2019. If you want to talk feel free to shoot me an email. neildeb2@aol

Click to expand...

Thanks. What would you see as a reasonable number of hours before a rebuild under typical conditions of usage and maintenace. Would a boat with 4500 hrs on the engines be a concern as far as hours is concerned.

At that rating I'd agree that they are likely turbo'd and probably have N70 injectors. If the OP is committed to life in the slow lane at 7-8 knots, then it might be better to exchange those for N55's or perhaps even N45's.

If he's looking at long 7 knots runs, say CA to Hawaii, then it wouldn't be healthy to run those engines as they are configured at 15% load at 1100 rpm for weeks on end. However, for life in the 8 to 9 knot range then there'd be nothing to change.

Regarding engine hours, that's a question for your mechanical during survey. They may be blown, burnt, rusted piles of junk, or might be ready for another 4500 hours.

Yes unfortunately engine hours are almost a useless indicator. If well cared for and used regularly 4500 hours for this vintage would not scare me and you might not have any major overhaul needed for many thousands more. As suggested a good mechanic would be the best person to give you some idea but it really is hard to know. How many hours do you expect to put on the engines?
If visually the engine room and engines are a mess that would raise a red flag. Unless redone you probably are not eating off the floors but I would be concerned about overall care and maintenance if there was gross neglect of housekeeping.

The Johnson and Towers version of the Detroit Diesel 6-71N was 310 bhp, which is 52 hp per cylinder.

At 4-71N would be 207 bhp at that spec.

A 175 bhp 4-71 is a Natural. Non turbo, and is a long life engine, at 44 hp per cylinder.