As seen in Speedboat Magazine’s August 2019 Issue.
Oil Pump Issues
I have a Schiada V-drive with a carbureted turbocharged 540 cubic inch big block Chevy coupled to a Turbo 400 transmission. Recently, I noticed erratic oil pres-sure and now it is very low, especially at idle. The motor has a solid roller cam, so I don’t hear any lifter noise, and seems to run OK, but I am afraid to run it. The oil pressure gauge is mechanical, so I think the low pressure readings are accurate. Can you give me any ideas of what the problem might be?
Jason Miller Parker, AZ
It is likely that your oil pump pickup has broken off or even worse, your oil pump has broken off the rear main cap. Standard and most high-performance oil pumps are made of cast iron and can fracture due to harmonic vibrations caused in a boat. Boats that have surfacing propellers and high-performance V-drives are more likely to have parts fail due to vibrations that are sometimes not detectable. If you are running a two-blade propeller on your Schiada, the vibration caused by the propeller (especially when getting on plane and at lower speeds) can cause damage to other components in the boat and engine. I have seen a few cases where the oil pump has cracked or broken off the rear main cap.
Your V-drive engine is mounted in the boat backwards. A big block Chevy has the oil pump mounted in the rear of the engine (driven by the distributor) and requires that the pickup is at the front end of the oil pan because when the boat goes on plane, and during acceleration, the oil is forced to the opposite end of the pan. Most properly built high-performance V-drive oil pans have a pickup assembly that extends to the front of the pan (rear of the boat) and has trap doors built into the pan to keep the oil at that end of the pan. It is also important that a good wind-age control system is integral to keep the crankshaft from picking up the oil at higher rpm.
Recently, I had a 24 Schiada V-drive boat come in with a TCM 1300 in it with a similar problem. It is a 564 cubic inch motor with a Whipple 8.3L supercharger. The boat uses a two-blade Menkins propeller and does vibrate quite a bit until the speed gets above about 50 or 60 mph. In this case, the propeller also had damage which made the vibration worse.
After the engine was removed from the boat and the oil pan was removed, it was discovered that the oil pump had broken off. Fortunately, a complete inspection of the motor and bearings revealed that no damage occurred as a result of an attentive operator.
There are a few resolutions to the problem. Obviously, converting to a dry-sump oiling system is one, but in many cases, there is not enough room for the oil pump system or oil tank. Another way to go is to use an external belt driven oil pump with a wet sump pan. This works well but also requires that you figure out how to mount and fit the oil pump system into your existing rigging. One concern with the belt driven oil pumps is that if you lose a blower or other belt, it can take off the oil pump belt which would likely result in instant drama and extensive engine damage.
Several of the oil pump manufacturers offer billet aluminum oil pumps that would be less likely to be affected by the harmonics that could cause dam-age to a cast iron pump. The problem is that they are not designed for a reverse sump pickup conﬁ guration. In the case of the 24 Schiada, I modiﬁed a Mellings billet pump so it would accommodate a reverse sump pickup. This was done by machining the bottom of the pump off (which is normally the pickup), tap-ping and plugging the oil passage with a half-inch pipe plug.
Then the housing was drilled and tapped to accept a pickup assembly into the side of the oil pump. A custom ﬁtting was made that threaded into the side of the oil pump housing that the original pickup was welded to. With this system, I was able to maintain the simplicity of the wet-sump system while building an oil pump that is basically vibration-proof.
It was also discovered that the propeller had damage, which probably contributed to the problem in the ﬁrst place. The propeller was also repaired.
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