Overheating alarm question

[archie.buchman]

I have a 1983 Johnson Outboard 70 hp.

I have replaced the water pump with the new kit and have installed a new thermostat.

We have connected it to a garden hose with the flusher. The engine runs fine but the alarm will go off after about 6 minutes idling. No water is coming out of the exit hole (exhaust) we do have a strong tell-tail. Should I continue trouble shooting the engine or do yall think everything is fine?

I think the thermostat is not opening correctly or that the garden hose isn't giving enough water to the engine through the flush.

Any thoughts or comments on what could be going on.

Any information will be much appreciated thanks.

 

[multimech]

Re: Overheating alarm question

The water hose is probably not putting out enough water, or you are picking up air with the water with the flusher. If you have one, use a bucket large enough to put the lower unit in water above the pickups and retry. Yams always overheat on the flusher, Johnrudes not so often, but they will too.

 

[multimech]

Re: Overheating alarm question

Also, make sure you are using Champion spark plugs. I have had false overheat alarms with engines that size that are using NGK plugs.

 

[Daviet]

Re: Overheating alarm question

If you have a strong tell-tale, it is an indication that the water pump is working. The tell-tale is before the thermostat, so your water pump could be working fine and the thermostat could be defective and cause the engine to overheat. I would not run it until you have figured out your problem.
You could remove the thermostat and see if it will cool properly, if so you probably will have to install a new thermostat.

 

[archie.buchman]

Re: Overheating alarm question

Will the motor start without a therostat? It seems like it wouldn't in my mind unless the started has a bypass on it.

If you have a strong tell-tale, it is an indication that the water pump is working. The tell-tale is before the thermostat, so your water pump could be working fine and the thermostat could be defective and cause the engine to overheat. I would not run it until you have figured out your problem.
You could remove the thermostat and see if it will cool properly, if so you probably will have to install a new thermostat.

 

[MichaelP]

Re: Overheating alarm question

I had the same issue recently with my 1990 E90TLESB. I pulled the t-stat housing and ran it. Water was coming out of the blocks just fine so I tested the stats with heat and they worked so now what you say? There is a small hole in middle of the t-stat housing and it was blocked. This caused a vapor lock preventing the water from getting into the housing.

 

[archie.buchman]

Re: Overheating alarm question

Just removed the T-stat and ran it. It runs great until the alarm sounds around 5mins of idle.

Should I move onto cleaning the cooling jacket?

 

[Daviet]

Re: Overheating alarm question

Are you sure it's overheating, maybe you have a bad sensor. Can you get a temp reading on the cylinder head, can you hold your hand on the cylinder head for a count of 4-5? How much water is coming out of the center of the prop, is it hot?

 

[archie.buchman]

Re: Overheating alarm question

No I can only hold my hand there for about one second.
Fine mist out the prop.

Got a new flusher too.

Are you sure it's overheating, maybe you have a bad sensor. Can you get a temp reading on the cylinder head, can you hold your hand on the cylinder head for a count of 4-5? How much water is coming out of the center of the prop, is it hot?

 

[Daviet]

Re: Overheating alarm question

If it is overheating with the thermostat out, I would pull the cylinder head and check the condition of the water passages around the block.
It sounds like you have plenty of water going in but something is not letting it out.

 

[archie.buchman]

Re: Overheating alarm question

Doesn't sound like fun. I might just take it in to the shop, seems like it is getting to be more trouble than what I am up too.

If it is overheating with the thermostat out, I would pull the cylinder head and check the condition of the water passages around the block.
It sounds like you have plenty of water going in but something is not letting it out.