Ditto on what Tenders had to say. Palmer and Universal A-4 have different footprints too so I'm not sure a Universal Diesal would be the easiest swap. You need to find the model number on the Volvo and then get the specs on the mounts and angles. Whats wrong with the palmer? I prefer diesels to gas but the cost is not always worth it as gas can be fine if treated properly.
You can make a light wooden jig that tells you exactly where the mounting points for the engine are in relation to the prop shaft flang. Bolt the jig right on to the prop shaft flange and bolt the engine mounts to the bottom of the jig, and there's your guide. Trim the cores for the engine stringers until they fit the space below the engine mounts, and then glass them in.
I love this never ending Story.......
Here are some things to consider when it's time for RePower....
Sailor-Mechanic-Handyman-Computer Geek...be honest with yourself !
1. Can you ReBuild an Atomic 4 on your own ? That makes it realistic.
2. The Ericsons under 30' are not worth enough to justify a new Diesel.
3. As you can not ReBuild your Atomic 4,abandon the Engine and go Outboard
4. Used Diesels are usually not worth the Time and Effort
5. ReBuilding a Diesel is WAY over the Head of most Garage Mechanics and the Parts Bill will equal a New Engine.
An Atomic 4 is really no more than a 4cylinder FlatHead Lawnmower Engine.
So if you are a REAL Grease Monkey and can Rebuild that old Atomic 4..do it !
Most Owners can not Rebuild these Engines and the 4cycle Outboard is a good option.