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Author Topic:   90hp Merc

BradB posted 07-07-2008 02:14 PM ET (US)
I have a 90 hp classic 3 cyl. merc. Motor was not running on all cylinders. Carbs and fuel pump have been rebuilt, fuel supply lines have been replaced and a water separating fuel filter installed. Motor now starts and runs well at idle. In gear it will jump the boat right up onto plane and run nicely for 5-7 minutes then turn off as though killed by a switch. After that it can be restarted once or twice, then it is dead until all has cooled off. After which we can repeat the above. Mechanic is stumped and says he can find no problem. Any thoughts?
brisboats posted 07-09-2008 12:44 PM ET (US)
Sounds like the switchbox (powerpack) going bad. But instaed of guessing, get a mechanic that can properly test your electrical system. Stator, coils and switchbox are all expensive and non- returnable components.
Brian
BradB posted 07-09-2008 03:15 PM ET (US)
Thanks for the input. I've thought it was electronic. Mechanic said "sorry, It ran on hose all day long, never shut down." I do have to get it back to him. Another poster suggests vapor lock, would that yield a sudden shut down?
Landlocked posted 07-09-2008 05:06 PM ET (US)
Perhaps this is too simple of a solution but have you checked to make sure the tank vent is open? I've experienced similar situation with mine when I inadvertantly left vent closed during operation. Motor will run until vacum becomes too high and then shut down. Letting it sit for a while might allow the vacume to release thus allowing a restart. Could explain why it ran at the shop but not on the water...
Ll.

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Author	Topic: 90hp Merc
BradB	posted 07-07-2008 02:14 PM ET (US) I have a 90 hp classic 3 cyl. merc. Motor was not running on all cylinders. Carbs and fuel pump have been rebuilt, fuel supply lines have been replaced and a water separating fuel filter installed. Motor now starts and runs well at idle. In gear it will jump the boat right up onto plane and run nicely for 5-7 minutes then turn off as though killed by a switch. After that it can be restarted once or twice, then it is dead until all has cooled off. After which we can repeat the above. Mechanic is stumped and says he can find no problem. Any thoughts?
brisboats	posted 07-09-2008 12:44 PM ET (US) Sounds like the switchbox (powerpack) going bad. But instaed of guessing, get a mechanic that can properly test your electrical system. Stator, coils and switchbox are all expensive and non- returnable components. Brian
BradB	posted 07-09-2008 03:15 PM ET (US) Thanks for the input. I've thought it was electronic. Mechanic said "sorry, It ran on hose all day long, never shut down." I do have to get it back to him. Another poster suggests vapor lock, would that yield a sudden shut down?
Landlocked	posted 07-09-2008 05:06 PM ET (US) Perhaps this is too simple of a solution but have you checked to make sure the tank vent is open? I've experienced similar situation with mine when I inadvertantly left vent closed during operation. Motor will run until vacum becomes too high and then shut down. Letting it sit for a while might allow the vacume to release thus allowing a restart. Could explain why it ran at the shop but not on the water... Ll.