1979 johnson 90 circulation problem?

[jamesdad]

i bought this motor for 200bucks running. when i first started it on the hose it immedietly gave water through the peehole. after about 5 mns the water got boiling hot and started to become steam. i shut it off and then removed the two rubber elbows on the back of the engine and flushed it with the hose. water will go inthe left head and freely come out the right head. so i assume im good there. on the bottom of those hose is like a manifold if i back flush through there it comes out the bottom of the drive. i reassambled the hoses ran it and it seems to be much better.my problem is now the left hose stays cool while the right hose gets hot along with the right head. what could be doing this? is there two seperate sides to the cooling system? any help would be great! thankyou in advance james

 

[emdsapmgr]

Re: 1979 johnson 90 circulation problem?

The telltale indicates that the water pump is functioning, at least to some degree. That water is pumped up to the powerhead, where it circulates through set passages, then passes through the thermostat housing on it's way out of the block. In that housing are two stats, one for each side of the block. If either stat is not functioning properly, the water will not exit that side of the block, and you can get an overheat pretty quickly. It's always a good idea to replace the impeller when you buy something new, so you know it's condition before your start out on your first boating activity. The same is true of the thermostats. You'll need to get into that housing anyway, to fix the stat on the overheat side, so replace them both. Check the condition of the pressure relief valves too-make sure they are not heat deformed.

 

[jamesdad]

Re: 1979 johnson 90 circulation problem?

are the thermostats under the cover attached to the two hoses? thanks james

 

[emdsapmgr]

Re: 1979 johnson 90 circulation problem?

The thermostat housing sits at the back of the midsection, below the powerhead, between the two heads that both hoses connect to. That thermostat housing is not the easiest to get to, but on a flatback engine like yours it's not too bad.