Exhaust bubbling out the lower unit

[NUTZ]

Hello All, I just started my 1968 40hp Evinrude Big Twin for the first time and I have a problem of no water spitting out the exhaust and exhaust bubbling out the lower unit. I have replaced the water pump and thermostat.
Maybe a bad head gasket or worse. What do you think?

Thanks in advance

 

[F_R]

Re: Exhaust bubbling out the lower unit

Are you running it on a boat or in a bucket? If in a container, it has to be deep enough for the water pump to be submerged and large enough to be in water and not be all air bubbles. It is supposed to bubble exhaust out the bottom. After all, it is underwater exhaust. The hole up above is just a relief for easier starting and idle.

 

[NUTZ]

Re: Exhaust bubbling out the lower unit

Are you running it on a boat or in a bucket? If in a container, it has to be deep enough for the water pump to be submerged and large enough to be in water and not be all air bubbles. It is supposed to bubble exhaust out the bottom. After all, it is underwater exhaust. The hole up above is just a relief for easier starting and idle.

Yes, I am running the motor in a barrel with the water line well above the lower unit. I am concerned because there is no water being pumped out like on my other outboards.

 

[Pony]

Re: Exhaust bubbling out the lower unit

There isn't a tell tale on that motor, so you aren't going to see a stream of water coming out. You should see water coming out of the relief ports on the back of the leg, especially once the tstat opens.

Here is a pic of my 62' running....you can see the water coming out of the port on the back of the leg.

 

[F_R]

Re: Exhaust bubbling out the lower unit

If the water is deep enough, something is wrong if there is no spray at all out of the relief hole. The amount of spray varies according to whether the thermostat is open. No spray, you have to retrace your efforts till you find out what is wrong. We can only guess. My guess is that you missed the holes with the water tubes. OK, so maybe it's a rotten guess.

 

[NUTZ]

Re: Exhaust bubbling out the lower unit

If the water is deep enough, something is wrong if there is no spray at all out of the relief hole. The amount of spray varies according to whether the thermostat is open. No spray, you have to retrace your efforts till you find out what is wrong. We can only guess. My guess is that you missed the holes with the water tubes. OK, so maybe it's a rotten guess.

Hey, it's a shot and I will give the water tubes a check. Also, would installing the impelled backwards cause this?
thanks

 

[Chinewalker]

Re: Exhaust bubbling out the lower unit

Hello,
There is no "backwards" on this motor for the impeller. As soon as you start it, the blades will right themselves.
Try some compressed air blown through the water tubes - not uncommon for an old impeller blade to get forced up into the motor, or for the grommets on top of the pump housing to get bound up on a misaligned water tube.
- Scott

 

[NUTZ]

Re: Exhaust bubbling out the lower unit

Ok, today I pulled the thermostat and started the engine to see if water would come out and to my surprise exhaust gas was puffing out along with a little water. I pulled the cylinder head cover to look at the water jacket and it looked fine. I then started the motor for a few seconds to see if water would pour out of the opened up head and now, not surprised only a little water spit out from where the water tube should enter and exhaust gas still puffed out. I just replaced the head gasket and exhaust gasket not too long ago and torqued them down accordingly. Do you think the water jacket is broke somewhere?

 

[F_R]

Re: Exhaust bubbling out the lower unit

Naw, check back into that water pump. What you are thinking would be extremely unlikely. If it isn't the pump, then the 2nd most likely thing is an air leak into the cooling system. Bad water tube grommets or something of that nature. Leaving the check valve out of the thermostat housing will do it too. In extremely rare cases, the gearcases have been known to crack behind the side water inlet, but let's not get into that just yet.

Exhaust is puffing out those places because after doing it's job to cool the powerhead, the water goes into the exhaust housing to cool it. With no water going through, the exhaust blows back.