jcbdigger wrote:
So here is the latest dilemma. Having done some due diligence on the ‘new’ engines that are the main selling point of one of these boats, it appears that the new long engines that were fitted were not supplied by Mercruiser but by a local automotive engine supplier who specialises in bringing in car engines from the USA. So the engines are in fact Chevy blocks and not genuine Mercruiser!
Opinion appears to be divided on if this is a problem or not. Certainly the Mercruiser Mag 350s are based on the Chevy blocks, but to me that does not make it a marine engine, even if it has been properly installed. You could argue that are they no longer really Mercury engines? Trawling through various forums seems to indicate that while the Chevy blocks can be used, there are still significant differences in things like the camshaft and other components between the marine and automobile versions, one person who is apparently ‘in the know’ indicated that the marine blocks are manufactured to much tighter tolerances. Overall my reading is the that the Chevy blocks are possibly OK as short term replacements but they are unlikely to have the same life expectancy as the proper marine version Mercruisers. My guess is that the current owners have implemented the lowest cost viable replacement and have then put the vessel on the market, you kind of can’t blame them for taking the lowest cost solution, but not sure I want to buy into the longer term ownership after that.
So my question is this, does anybody here know if this is a real issue or not? Are the Chevy long blocks an acceptable replacement, is this a real issue or is my concern misplaced? Right now it does not look and feel right and my instinct is to run away towards the alternative vessel.
Mercruiser 350s and Volvo Penta 5.7s are both made from Chevy Long Blocks supplied by General Motors (GM). My understanding is the only differences in the marine long block are the Camshaft (which is different for each HP rating), the brass freeze plugs (not steel), roller lifters on some models and roller rockers on some models? (I'm not sure there). The thermostat housing is different, the circulating water pump must be marine rated (SST or brass impeller). The oil pan may be larger (if part of the long block)
External items are supplied by Mercruiser or VP and are different from automotive: Intake Manifold / Carb or Fuel Injection + Fuel Pump(s), Spark Arrestor (instead of intake air filter), Exhaust manifolds, Marine Starter, Marine Alternator, Marine Distributor, Raw Water Pump, Engine coupler, Engine mounts, a nice matching paint job, and a pretty plastic cover over the intake area.
So I don't call the Chevy block a downgrade or a temporary solution. However, your post still doesn't answer weather these are "New" long blocks from GM, or if they are rebuilt by an aftermarket company. Most likely they are rebuilt.
I would consider these "newer" engines to be more of a neutral factor, but as mentioned earlier, not necessarily an upgrade, unless they were Factory New long Blocks from General Motors.
Ray
_________________

"Knot Easy" 2000 Horizon 240 Volvo 5.7GS /SX
tow: 2017 Honda PILOT EXL-AWD
prev. boats:
'87 Chaparral 198CXL 4.3 OMC Cobra
'69 Jetstar 16ft Ski Boat, 115hp Yamaha
'68 Aluminum Jon Boat, 3hp Sears
'64 Water Wings