Repowering a 54' Donzi Sportfish

I'm starting a new thread to cover the Repower of my 1994 54' Donzi (by Rosciolli) Sportfish. Today I formally placed the order for CAT C18 ACERT 1150 hp engines and ZF665A gears. These will replace the existing Detriot 12v92TTA's. In addition to the engines and gears I am also replacing the generators, propulsion controls, oil change system and likely other items as well that make sense while we are torn apart. I'm still making final decisions on some items and will post once I have info.

To swap engines we have to cut out the salon floor and aft salon bulkhead as there are no hatches. Today we started removal of Settee's, carpet, dining tables, cabinetry and joinery work. We have done our mock ups and laid out the access cuts. The boat is scheduled to be hauled and go into a building on 9/26. I'll document progress and post pictures as we go along.

My lead guy has been doing detailed layout and mock up the last few days. The good news is the holes in the deck/engine room ovhd will not need to be as large as we thought. We will separate the engine/gears and have a sequence to be able to get the items in/out along with the gens. By doing this we do not have to touch any of the galley equipment or cabinetry, etc. The window in the aft bhd is not large enough. We will be cutting just above the cockpit freezer and below the flybridge. But will leave enough room for fiberglass overlays going back. I spoke to CAT and they have no issue with us separating the gears from the new engines since they work with us regularly and know our capability. In the attached picture you see the galley island/bar with granite countertop. By reducing the deck hole size this can now stay in place. Boy things sure get ugly in a hurry when you start tearing things apart!

I should be receiving the final quote from Northern Lights shortly. I am going with the 20kw and 9kw, with sound enclosures, secondary isolation mounts, high output 12v alternators to charge 12v house bank and digital gauge panels.

I'm also ordering the Reverso GP-806 oil change system. This package is way better than the pump and manifold system original to the boat.

Now I'm researching the option of using an electric power steering pump to feed the Hynautic steering. The existing system has an engine mounted pump and cooler on each engine. If I can find a suitable electric pump I can eliminate the need for a second set-up on the other engine and will have more flexibility of where to mount things and reduce the number of hoses.

I'm also considering upgrading my watermaker now too. The existing system is an old modular unit with pumps in different places, a manual control panel in the engine room, and filters in the lazarette. With all the equipment that is being removed I think I may have a good spot for a contained package unit fwd of my stbd fish box. But I would need a remote panel to control it. Any suggestions?

I wish you had photos too! If memory serves you went to bigger engines. The C18's are near identical to the 12v92's, actually a smidge smaller. On the port side we will decouple the gear, slide the engine fwd until up against the fwd bulkhead, then remove the gear and small gen, then we can slide the engine aft and get it out with the deck hole aft of the island.

The C18’s are approx. 1” shorter than the 12v92’s

I need power steering even if I'm only running one engine. I do long hours of slow speed trolling on one engine only. I wouldn't want to have all those hours be on one side only. So that's why I'm looking at electric so I have only one pump and cooler but it is running regardless of which engine is running. I have to try to figure out how much pressure and flow is needed so I can find the right electric pump.

I don't have any room under the cockpit sink. We reconfigured that about 5 years ago and made that whole area into a custom tackle center with 10 large drawers. There is quite a bit of room in the Laz fwd of the stbd fish box now that the trolling valve and gear selector actuators and cables all go away. Where do you have the control panel for your watermaker?

Have you called Hynautic to see if they offer something?

Not yet. I'm still trying to sort out gear ratio issues with ZF. I no sooner think it is resolved only to find issues with delivery time, discontinued ratios, etc. Hoping to have more info today. Once I get everything set on the big stuff (engines, gears, controls) I'll start on the other items.

I was really hoping to keep the 2.5". I'm currently exploring 1.525:1, 1.757:1 or 1.9:1. I realize the 1.9:1 is probably best option but I'm guessing that drops my safety factor below 3 on the 2.5" ? How much difference will there really be in performance? And, of course, if I change shaft size then I have no choice but to do props as well.
I know when Donzi 54 repowered he indicated he was able to bore the existing struts and go up to 3" shafts. I don't know about the hull shaft entry? Perhaps Donzi 54 will weigh