Re: 86 cobra 4.3 20rg.s to hot question?
Re: 86 cobra 4.3 20rg.s to hot question?
Yes that is correct, on the muffs you will not get as much water and it's not a true test. Put it in the water, disconnect the raw water intake hose at the thermo housing and then point it straight up, have someone start the motor briefly and see how much of a column of water you get, should be at least 2".
I am still suspicious of your impeller/water tube in the drive. If the 4 outlets were open, I think it might not be the manifolds. Did you hook up a hose to the mani inlet and see how well it flowed? Esp after all the rust you got out. Remember my pix? Well even after I changed those old manifolds for new, it still ran hot. It turned out to be low raw water flow, because I had barnacles growing in the water intakes, had good manifolds and good impeller and it didn't run hot on the muffs, or at low speed on the water, but on plane it would creep up to 185 which was too hot. I cleaned out the water intakes the best I could and it was back down to 165-170 like before.
There are 2 seals on that water tube that could be bad and not flowing enough, also, make sure that your impeller housing gasket is on right. If not it can pull in air when its on plane. One way to check is to remove the impeller cover on the upper unit and run it on the muffs, look to see if any water is leaking out around the impeller housing, there should be no water leaking out, if so try slightly tightening the mounting bolts. If it still leaks you have to replace that gasket. I seal em with OMC gasket sealer.
If you are getting a temp of 160 right under the thermostat, that's good actually, but your manifolds are too hot. Mine ran at 115 idle, 125-130 after running on plane. So either you have low water flow because of impeller housing leaks, or water tube leaks (also you checked the PS cooler for clogs right?) or possibly the thermo housing necks that the manifold feed hoses are connected to may be necked down from corrosion, did you take a look in there? All the corrosion you pulled out of the manifolds, you can get that in the thermo housing too.
If you do have to replace the manifolds, you know that those batwings are no long available, the last time I bought a set (2004) they were almost 400 a piece. There is a 2 piece conventional set up out there that would work though. I did like the one piece units because there is no gasket to leak which can cause problems on any raw water cooled I/O.
Glad you got it, I could see dings on that impeller plate and the cage that the impeller lives in looked like it had some wear marks on it. I usually replace them every 2-3 seasons unless something happened like sucking up sand. The Cobra impeller is actually pretty durable. A couple of tips, make sure that cage is centered in the impeller housing, I like to glue it in there with a little OMC gasket sealer (it says to do this in the factory shop manual), the wear plate you can flip over and clean up the reverse side and re-use it if the back side is in good shape. I also use OMC gasket sealer on the gasket for the impeller housing. The next time you change it, try this. With the impeller housing off, hook up your ear muffs to the lower unit, put the hose on full blast and then squeeze the muffs tight to the lower unit so the water does not spurt out around them. With the impeller off, you should see water come out of the water passage on the right side of the spot where the impeller mounts. The water enters the housing from that right side opening and gets pumped into the transom house through the left side opening. It takes a full blast of water to get it up there though. I took your pic and labeled it so you can see how it works....
