06 Sundancer 320 with low compression

Hi everyone, I’m in the process of buying a 2006 Sundancer 320 with twin 350s (1000 hrs). The mechanical inspection showed the following:
- Port engine had compression values ranging from 160 to 190, and the mechanic’s suggestion that it’s probably due to bad exhaust
- Starboard engine had 0 compression on cylinder 3, but the rest were in good range

The seller is looking to negotiate the price down, but I’m concerned that even after the repairs (rebuilding both and replacing exhausts) it might still be something else and I see problems again after a season or two.

I have zero knowledge on inboards so would like to hear your thoughts here, thanks a lot!

My two cents: even with new heads, or rebuilt longblocks where they re-use all the existing accessories -- it's still 1,000 hours. I bought my boat (similar era as the one you're looking at) with almost 900 hours on the boat but both engines had the longblocks replaced, with low hours on them by the time I bought it. Now they run fine and have great compression but I'm slowly having to replace sea pumps, water pumps, thermostat housings, sensors etc which is to be expected.

Best case scenario: the seller does a complete re-power but that's unlikely just for the sale.

1,000 hours for a boat of that age would be fine with me, since it means it was used and didn't just sit around. But I would want to see records to make sure the seller kept up on maintenance.

The 320 is a great boat. There are a couple on the same dock as me. I think the seating layout is awesome. The one thing that would scare me is bilge access to work on the engines.

Thanks for the input! yeah I feel the best option is to repower with crate engines and have new manifolds/risers/elbows put in, but I doubt the seller would want to discount the price by that much.

The boat is super clean but it seems they weren’t diligent on the maintenance since the exhausts were pretty much the original.

0 compression is really bad - did the boat even get on plane? that boat has to work really hard with and kind of load - it is marginally powered at best - very hard on the motors - yes, it needs 6.2 drop ins - your looking at 20k - do shaft seals and new water pumps at the same time - that boat is super tight in the engine room - the owner would be better off patching it up and finding a different buyer

Have them do a leak down test to get a better handle on the problem. Then make your decisions from there. Good luck.

Ididntdoit said:

0 compression is really bad

Click to expand...

I would put that over in the best quotes thread

Not really, most likely a valve stuck open.