Why does the engine quit and not restart in water ?

Question

marine 302 with a volvo 170 out drive. 1974 Wacashaw. Runs great on land starts right up. put it in the water runs great @ 5mph for 10 to 15 minute then dies. wont restart for 10 or so minutes or not at all. Take it home and flush engine will sit and run for as long as i sit there. Rev it etc. will throttle down and keep running. carb is rebuilt, new plugs points wires coil condenser. good even compression. HELP! we are tired of paddling.

Answer 1

check the fuel filters and also check the vent for the gas tank  make sure shes venting and not blocked

Answer 2

Nothing weird about it.  It's common for an engine with underwater exhaust to sound and run fine out of the water then c**p out when you submerge the lower unit.  Backpressure on the exhaust puts a load on the engine.

You replaced plugs/points/condenser, but did you do a spark test afterward?

Recheck your carb float height.

Make sure the fuel line is holding pressure.

Check the tank for debris and/or water.

Answer 3

i would bet you are vapor locking or your fuel filter is plugged. out of the water it needs very little fuel but in the water its working so it needs more fuel. when it starts using more fuel maybe it picks up water in the fuel and plugs your filter

Answer 4

Water pump impeller is probably shot. At home you're probably running it with earmuffs to supply water. The garden hose is physically forcing water in to the engine keeping it cool. Out in the lake, the water pump isn't pulling enough water to keep the motor cool and it's over heating. The impellers dry up or even suck in fishing line and get destroyed, try changing it, they're cheap.

Answer 5

sounds like the needles/venturi may not be dialed in correctly in the carb.

You are still on land and the fuel isn't moving around as you would on water. Check the manual for the correct metering of the carb.

Answer 6

thats a weird problem it sounds like somehow its not breathing it needs air if its a out board then see wat you can do about bringing the prop a little bit more out of the water ive never had this problem myself tho good luck