Boat starts in driveway and on water but not on ramp

[jclarke2899]

I have a 1998 four winns with a 502bpbyc Volvo/OMC 5.0GL engine. It starts with turn of key on muffs in driveway, idles well, gets to temp. I get it on the ramp and it cranks and cranks. Normally can finally end up getting it going, but can’t figure out what the cause is. After I get it going and pull away I can get to WOT, stop restart 10 times and no issue. Seems like something with the angle while on ramp is causing this. Thinking maybe water in the fuel so going to drain tank. Any ideas or similar experiences?

Boat has good compression, new plugs and wires.

 

[kenny nunez]

If there was water in the carburetor it would not go wot. Get a volt meter, check the voltage at the +or bat side of the coil while the engine is cranking.
There has to be 12 volts when the engine is turning over. If below that or no voltage then the ignition by pass circuit is the cause. The starter relay has a terminal that may have an I with a purple /black wire. Most cases the relay is the problem. Volvo also uses square Bosch style relays. The wires are red/yellow, red, black& purple/black.

 

[jclarke2899]

If there was water in the carburetor it would not go wot. Get a volt meter, check the voltage at the +or bat side of the coil while the engine is cranking.
There has to be 12 volts when the engine is turning over. If below that or no voltage then the ignition by pass circuit is the cause. The starter relay has a terminal that may have an I with a purple /black wire. Most cases the relay is the problem. Volvo also uses square Bosch style relays. The wires are red/yellow, red, black& purple/black.

So what do you think the angle of the boat would have to do with this? Started again today on muffs and fires right up.

 

[kenny nunez]

Just to be sure do the voltage check. That will narrow down the problem.
A low or no voltage by pass circuit is real intermittent.
Remove the flame arrestor, hold the choke open and have someone pump the throttle a few times look into the air horn to see if the accelerator pump is squirting fuel.

 

[froggy1150]

Check/adjust floats in carb?