1977 70hp johnson runs good for 5 min than bogs down

[Councilmen]

Son took boat out hit sand bottom at full speed runs like crap could he have sucked sand into the bottom end and tube? Runs good for about 5 mins than bogs down?

 

[SeaKaye12]

Re: 1977 70hp johnson runs good for 5 min than bogs down

Are you suspecting overheating? Is the telltale strong and is the block "touchable"?

Ignition issues often cause the symptoms you are describing. A component fails in relation to temperature and you may be dropping a cylinder. Do a spark test when the problem occurs.

Could also be fuel related; you might have some crud that randomly works it's way into the main jet area.

 

[Councilmen]

Re: 1977 70hp johnson runs good for 5 min than bogs down

Sorry the "telltale" is that the water
Output and if it is it is very low after about two months he tells me he hit bottom suspecting water pump?

 

[dmoriarty51]

Re: 1977 70hp johnson runs good for 5 min than bogs down

stop running it and remove and inspect the water pump. if you continue to run it you'll be looking for a rebuild or a motor