1960 merc 300 idle problem

[cbouch]

i have a 1960 merc 300 that until now has been the sweetest running motor that you could hope for. Put the boat in the water for the 1st time in a year...pumped the ball, got good pressure..started right up. Would not idle...fast idle ok...after fooling around with throttle and gear shift got it running great at higher rpm but idle or slightly above stops. If you squeeze the ball motor keeps running..I am thinking it is the fuel pump at fault...high speed lots of vacuum sll ok...low vacuum not enough to pump the gas. Appreciate your advice. Thanks cliff

 

[James R]

Could be the pump but with todays gas and If you are not using Stabil additive I would look to the carbs first.
As simple routine the first test is always a compression check. The next is a spark check .Then the carbs will probably need cleaning and rebuilding with new kits.If the carbs have not been addressed in the past two years they will probably need doing. A bad performing carb will burn out an engine..

 

[cbouch]

Fuel used is 91 octane non-ethenal with stabile added...but appreciate your advice on rebuilding carbs...maybe do the fuel pump and carbs. Thanks, cliff

 

[DeepCMark58A]

Stick with your first thought, rebuild the fuel pump. Use genuine Mercury parts and check the fuel lines.