Which side is the low point ?

[Brysherexx]

When I go to the lake and let the boat idle on the trailer the normal amount of water comes out of the passenger side exhaust but hardly any thing comes out the other side. I have logs and the valve is opened all the way. When I run the boat at home with the hose on full blast (and the boat running) the water pours out both sides like it should. What gives?

 

[Shlbyntro]

When I go to the lake and let the boat idle on the trailer the normal amount of water comes out of the passenger side exhaust but hardly any thing comes out the other side. I have logs and the valve is opened all the way. When I run the boat at home with the hose on full blast (and the boat running) the water pours out both sides like it should. What gives?

slight back pressure differentials in the exhaust and exhaust side cooling system cause this. it is nearly always indicative of a low water flow condition

 

[sintax]

When I go to the lake and let the boat idle on the trailer the normal amount of water comes out of the passenger side exhaust but hardly any thing comes out the other side. I have logs and the valve is opened all the way. When I run the boat at home with the hose on full blast (and the boat running) the water pours out both sides like it should. What gives?

I think you answered your question there. Garden hose can be upwards of 40-60 psi at the end. You're pressurizing the system and could prob run w/o a water pump at that point.

Was the impeller serviced this year? if so you might have some obstructions