How much smoke is too much for that 40hp engine?it mixes it’s own oil,it resembled one of them e cigarettes.after running for 30 seconds roughly

SOURCE: 1999 bravada oil

check for coolant in the oil. remove the oil fill cap and look for a white milky substance. most likely engine damage has already occured because to have that low if oil pressure there is too much "clearance" between the bearings and the components they work with-(crankshaft,camshaft,connectiong rods). that vehicle came with dexacool coolant and it would shorten the life of the intake gaskets. they then would leak into the engine ruining the bearings over time. the skip can happen from lifters hydrolocked with the oil/coolant solution. take it to a reputable mechanic for an analysis......Good luck.......Scott

SOURCE: White smoke coming out of exhaust even when engine is warmed up.

on the 3.8 ussaualy not the head gasket but the upper intake gasket . antifreeze leaks inside intake and into the cylinder. very common. the new gaskets are much thicker.or the plastic plenum the black plastic part on top of the engine goes bad around the water inlet and need to be replaced . when i do either job itell the person to replace both at same time saves money and headaches in the near future. hopes this helps .....and cost for a shop to do this $1100 to $1500

SOURCE: White smoke from my Craftmans tractor,

Use the lawnmower's oil dipstick to determine whether the oil level is correct. Maintain the correct level of oil. If you've overfilled the oil, open the drain plug, and drain some of the oil into a waste container.

Dispose of any excess oil properly. Burning off excess oil is undesirable. It can foul the mower's spark plug, piston rings, and other engine components and contributes to air pollution.

If your mower's engine has not been overfilled with oil, but still is smoking, it may have stuck or worn piston rings or another maintenance problem.
If it has sat over the winter, and didnt have stabilizer in it - it may be bad gas too. Drain it out, and put in fresh.

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SOURCE: 40hp 1987 yamaha outboard motor will run for 30-60

Sound like the fuel pump is not keeping up with the engine's demand. Check it out. Good luck. Hope this helps.

SOURCE: it starts fine, runs 20-30 seconds, runs rough,

check the actual fuel line. Also is it fuel injection or carberator