Cat Gensets

I was involved in a total repower of a 50 meter Benetti in 2011 for the Mains and Gens and Cat didn't have a lot to offer in the 60 to 90 KW range. The 4.4 Acert is a Perkins engine painted Cat Yellow swinging a Stamford alternator with Woodward controls BUT at a price point of $35,000 for a 80 KW with sound enclosure that's a hard deal for most owners / Captains to pass up compared to the same Northern lights 6 cyl. 86 KW @ $ 140,000. The owner went with the 4.4's & they were replaced within two years with less than 3,000 hours on them. Rear seals let loose twice on both units, ECM problems , speed sensors to name a few. The C-9 that I've had aboard vessels as generators are notorious for their HEUI pump failures and ECM problems. The C9 as a main engine would make more sense but they didn't fare well as generators. I don't know what size vessel that your building but unless your looking @ 150 KW and up then Cat hasn't much to offer and for that matter Kohler has more than their fare share of troubles as they were standard spec. equipment on Christensen yachts as I was the build Engineer on Hull 034 "Odessa" and the boat has had nothing but problems with all three Kohler's one 125 KW and two 90KW units to the point that I believe several of the new Christensen hulls are calling for the Cat C- 6.6 unit and I'm not familiar with this engine and haven't been involved with it in the field. Any feed back on this 6.6 K1W1? Hopefully it will be a good machine as I like the Cat engines for Main propulsion 3500 series & customer support network.

I would go Northern Lights in your application based on the info given above and the fact that Northern Lights has been producing solid generators in your size range for decades upon decades and mostly for commercial fishing boats that need reliability and such.

As of 6 months ago the lead time for a N.L. 85 KW gen was eight months so what ever you do have the builder figure out the load calculations for KW rating and I also recommend taking the interior designers lighting choices into account as a few builders have made their calculations only to then have a "inferior desecrator" come in with a crazy lighting plan and kill it. LED is the way to go these days. No more of fifteen different bulb sizes and wattage to deal with.

Oversizing a generator by 20 percent is not the way forward here. if in fact your going with a PMS onboard it would-be better to be right on the line @ 90 percent maximum operational load and 75 -80 percent normal load and let your PMS bring the second gen on the buss until the load drops. This is pretty hard for a lot of builders to get right so either they throw load banks aboard or always seem to undersize one gen and oversize the second gen. Of course the night time load is going to be the lightest and at that point your not going to have the proper loading for the engine without load banks. loading a yachts generator for optimum engine performance at all times of the 24 hour clock is difficult. I've been following Marmots posts for his proprietary systems that Deangelo is now using and don't know if it could somehow be scaled to be used as a sort of smaller load bank with the effective burning of your exhaust.

Sorry, I wasn't to clear on that. I have to be careful here, A few builders will perform a load analysis and come up with an estimated KW load factor and install the #1 gen to that factor then over size gen #2 to take up any miscalculations brought up earlier such as lighting or customer change orders that might require more KW from the already selected and installed machinery.
If you select two identical units with PMS than you can use the load shedding option the PMS gives you by auto dropping the non critical loads such as boilers, half the AC compressors, the hot tub etc before it automatically parallels the second gen. It is better to have your PMS auto parallel as some of the equipment dropped on non pref will have to be reset, things like freq.. Drives or motor starter circuits. Get a verifiable expert in this field if it's early enough to still do so.