31 HP Commercial Briggs and Stratton

[jolivier]

I just bought a mud boat and it has a 31 HP Briggs and Stratton commercial V Twin engine installed. The engine Model is 543477-0110E and the Code Number is 04030112.

The engine will start with no trouble and will idle normally. When it is accelerated quickly at no load the engine quits firing until the rpms have reduced to a fast idle. I have the service manual but don't see anything in the ignition circuitry that would result in this phenomenon.

I don't know if this is normal ( like an overspeed device activating) or a problem. Should the engine be able to operate at wide open throttle at no load ??

If so any ideas as to the cause would be appreciated.

[StarTech]

Engine has 3600 rpm no load max speed using a mechanical governor. No reason for it to electrically quit firing.

Are you sure that you don't have carburetor problems instead? The high ports clogging would explain the lack of fuel causing the engine only run at high idle.

[Deere2me]

You may wanna check online for an owners manual for the COMPLETE unit. It may have an overspeed device/sensor that would kill the mags in case the prop came out of the water or something . I'm only speculatin' though.
One way to check is unplug the kill wire/s at the coil, or harness if ya can isolate them.

[jolivier]

The problem may have been low oil. This engine is mounted in a boat as a straight drive inboard. Off horizontal it is around 15 degrees down at the drive shaft end which connects to a shaft coupling. I had checked the oil in this configuration and it showed full. We removed the engine to do some work on the hull and while it was sitting horizontal on the floor I again checked the oil. It was showing quite a bit below the "Add Oil" mark on the dip stick. I think the problem might be that in the boat the oil pump at high revs was not generating sufficient pressure since the oil was pooled at the back of the sump and the engine would cut out on low oil pressure. I think I'll fill the engine to the normal full mark in the horizontal position and check this again once it is in the boat again.

[KE4AVB]

Thanks for the extra background info it does help to know your operating conditions especially when they are out of what we normally deal with.

That could be very well the cause your engine shut down if the engine low oil pressure switch was indicating low pressure due lack of oil at the pump. Being at a 15 degree and the boat also accelerating would cause the angle to increase even more as the back of the boat drops down on the initial start-up. Plus with acceleration the oil would push to the back too.

Don't hear much of the use as boat motors but I do remember helping a member over on Perr site last year that mounted one to a shaft to drive a propeller shaft on I think a flat bottom boat.

One suggestion if this proves to be your problem. Fill engine while it sitting in normal flat position and then when it is mounted in the boat at the the 15 degree angle check it again. This notice where oil is on the dip stick and with something inscribe a new full oil level indication mark. Use something like an engraver or similar marking tool. After this inform the operators of the new oil level mark use.

[jolivier]

Thanks for the suggestion. I was thinking about doing as you suggested but was concerned that the build up of oil in the rea of the sump when underway would somehow be injurious to the engine.

Any thoughts.

J

[KE4AVB]

If it was a dipper style oil system I would weary about the oiling but since it a pressurize system it should be safe as long you don't get too extreme with the angle. just don't standing oil covering the breather port, being in the cylinder area or blocking any drain back holes. Just not familiar at all with this type of application to be much help maybe others can.

[jolivier]

I understand that you are not sure either but you have been more help than anyone else to date. At least I can bounce my ideas off of you and get a reality check.

Thanks

J