Reply With QuoteYes...........
Hey guys, I'm curious as to what the basic differences between a BBC for Marine use and one not for marine use. I know in cars running a BBC at high RPM for any length of time will kill it quick - will running a Jet at 4600RPM for a length of time do the same?
Thanks for any info or thoughts
Yes...........
It's been long debated, the differences between the auto and jet engines. the Hardin engines came a drive packages, and I don't know the perticulars of the internals. Some other jet set-ups, used off the shelf marine conversion parts, removing manifolds, water pumps, and smog systems, and slamming on the marine stuff. I one point, I've read, boat manufactures, going to pick up engines right off the shipping docks, because of demand in the day. Perhaps OldRigger can fill in some blanks and answers here. But then again, how long did some of these set-ups last?? It's easy to toast a jetboat engine if you don't have a clue, as to what your doing.
Sleek
I've seen a GM performance parts ZZ572 crate engine used in a boat before.
Among other crate engines. Is this not the way to go?
We use ZZ4's in my particular race class. We usually get between 100-200 hrs out of them, I've seen shorter and longer. It's the box stock ZZ4 as built by Chevy, no marine changes. Chevy even says not to use it as a marine motor. We use them at 2 speeds, sitting on the trailer and WOT. We frequently run them WOT for between 10-40 minutes, yes minutes, with the pump loading/unloading frequently. In one race which is not particularly long for example, I ran at WOT up river twice on Saturday for about 15 minutes each, twice down river for about 15 minutes each and then repeated on Sunday. I didn't change anything including the oil at all during that race. I got a little over 140 hours out of that motor (its wasn't quite up to ZZ4 specs, maybe a little down on comp ratio and cam, we'll call it about 320 HP). This is only one example and its a SBC, but I think its safe to say a car motor can reliably be run in a boat if the set up is right and certain precautions are taken. I wouldn't try this with a 455, but we are getting similar results out of the ZZ502, and some people north of the border are experimenting with the ZZ572. Yes, my motor is currently smoked but I'm saving up for a new ZZ4. There's a lot of controversy surrounding this topic and quite a few previous threads. These are my results with one partucular type of motor, and I think its safe to say we run them as hard as anybody can. Anybody done this with any other factory motors in a more lake oriented environment so we can see any other results than a SBC?-Aluminum Squirt
ASquirt,
When it did break..........What broke? Was it catastophic?
Did you pull it all down to take a look? What other kind of damage did you find?
:boxed:
It's still sitting in the boat. Looks/sounds like maybe some collapsed rings, cracked head or block, burned piston or valves, something along those lines. It's actually been blown for a long time, just haven't had much time to pay attention to it with a new kid and all. Symptoms were LOTS of blow by coming out of the breathers, very low compression in one cylinder, and generally poor running. I'm pretty sure with the above symptoms it was running on at most 7 cylinders. It didn't help that I had just swapped carbs and ignition, I'm sure there was a lot of tuning of those items that needed to be done that was making everything else worse. Not that a carb/ignition swap caused any of it, just with major components way out of tune, it was hard to get a handle on the symptoms and get it nailed down what was wrong without pulling it apart. Oh well, that's racing. I'm saving my pennies for a new ZZ4, hopefully when I get one I can do the autopsy and see what I broke, maybe even build the old motor to ZZ4 specs and have a spare on hand-Aluminum Squirt
The cams are them main difference. On a boat you mostly see high RPM's. Stock car cams are mostly for making power at lower rpm's. A car motor will work, just depends on how fast you want to go.
ddevore, There are several differences if you want a boat motor to live. First and foremost is the oil system, additional capacity, and sump management. Another "must do" is the piston to wall clearance. Since most marine applications are "cold" water cooled, the block does not expand as much as in a closed recirculating system. The piston gets just as hot as a car, and expands inside a cold water cooled block, so without the additional clearance the piston skirt will scuff and gaul. Automotive clearances vary by piston makers, so do marine, but a ballpark number would be .004/.005 MORE (+) for marine use. Total, maybe .008/.009, where car stuff is usually .004/.005 TOTAL. These numbers are open to changes, based on who is doing an engine, and what their experiences have taught them. You have to remember, boats do not coast. Meaning that when to lift, you slow down rapidly. In a car, after you reach cruising speed you can feather the gas back and still maintain that speed. Not so in a boat, you need to keep the Rs up, and that is one reason boats are so hard on motors. I'm can't say that car motors won't work in a boat, but I will say they don't work as well as an engine built for the type boat it will be used in. (jets and props are different). Happy boating................MP
Thanks for the info guys. My boat's got a Marine engine in it and it probably always will. I was just a little concerned about the higher R's that I run to keep it outta the water, I've heard from some hot rod guys that a BBC was made more for lower RPM's than this pig needs to even get on a plane - but I have a feeling some pump work (or swap out entirly) is soon to come,
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