norcalrider |
04-13-2011 1:45 PM |
From another forum that has a long thread on this subject:
Quote:
The longevity is an issue with the raw water cooling, especially if the boat will ever see salt water. An automobile engine is cooled with, preferably, antifreeze, but even straight water will neutralize itself and stop eating away at the metal parts. On a boat, you have a constant flow of new water, which leads to a higher rate of corrosion. Two areas that are usually "marinized" are the head gasket and freeze plugs. If you are rebuilding the engine anyway, get the marine head gasket, and make sure the freeze plugs are brass instead of steel.
Safe and legal are mostly fire/explosion issues dealing with the fuel and electrical system.
FUEL:
The marine carburetor will be a little different, designed so that the float bowls don't vent into the engine compartment, although the differences are rather subtle (at least to my eye).
The fuel pump has one major difference: it is designed to contain the fuel in the event of a ruptured diaphragm. It is common for a fuel pump to fail by rupturing the diaphragm, which allows gas to leak onto the side where it wasn't intended to be. This gas will then either leak out onto the ground or into the crankcase. For a car, onto the ground is preferred, but on a boat either case is really, really bad! A standard solution to this problem is to have a double diaphragm, with a drain between them. If the primary diaphragm ruptures, the gas will be contained by the second diaphragm and flow out the drain. This drain typically has a hose (usually clear) attached to it which leads up to the carburetor intake. Any gas that leaks is dumped into the carb, and if the leak gets bad enough it will flood the engine, which is a lot better than blowing you to smithereens!
ELECTRICAL:
Starter, alternator: rotating shafts with electrical contacts, they make sparks! Sparks will ignite fumes! To prevent the sparks from blowing up the entire boat, a marine starter and alternator will have flame suppression on the cases. The starter and alternator are NOT sealed, they have what is essentially a flame arrester between the source of sparks and the outside. It is possible for a small amount of gas fumes to enter the starter/alternator and be ignited, but the case will hold the small explosion and the flame arrester will prevent the fumes in the boat from being ignited. This flame arrester may look like nothing more than a small screen, but it is so important!
Distributor: Same flame arrester idea as the starter. The advance curves for an automobile are usually not the best for a boat, so you are better off with a marine distributor anyway.
While the fuel system modifications are intended to prevent any combustible fumes from being accumulated, the electrical system is designed to not ignite any such fumes that might be present. You may consider it redundant, but there are other ways to get gas fumes in
(such as while refueling) and other sources of ignition.
I highly recommend that you purchase the marine versions of the starter and alternator. You may choke when you see the price tags, but consider this: gas fumes are heavy, they settle to the bottom. The starter is located about as far down as anything can be. Gas fumes are most likely to settle when the boat is idle, which means that the starter is most likely to be the first electrical item operated. Starters, with out a doubt, make sparks. In other words, the greatest hazard comes from the starter.
Rod McInnis
And another:
I had a target engine (off the shelf from a dealer) rebuilt when it spun a bearing. The rebuilders used a different cam (for the nature of the use rather than highway), racing timing gears and chain (usual higher revs than automotive) and brass vs. steel freeze plugs.
Dropping in the marine electronics (mine was carb, so your application might be different) including the brain and distributor (no spark) completed the deal. Runs like a champ.
So, there's not all that much different. If you don't already have the exhaust manifolds, that will be extra, but isn't really marinizing the 'engine' - and you'll want the marine alternator and starter, probably, too, for the same no-spark reasons. So, all the "hang-on"s will likely have to be bought new or used, but the engine itself doesn't need much modification.
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