Dry Joint manifolds - ONE HOT, ONE COLD - is this ok?

[spunkyman]

I just got a 2007 Tahoe Q6 has a 4.3L Carb Mercruiser engine with dry joint manifolds and risers.
I was out on the lake and noticed that the temp was around 150-160 with oil pressure up around 70psi which I imagine is normal. The problem is that when I have the engine hatch open, looking at the engine, the riser on the left is HOT and the one on the right of the engine is COLD.... I removed the HOT riser and found no issues at all as far as water. The manifold still has water in it, so it's obviously flowing to there. The manifold itself looks to be in excellent condition with no blockages. Also, the spring loaded ball at the Tstat housing moves freely... I guess the water might not be getting to the riser? Wouldn't the temp gauge pick this up?
My question is .... is this normal to have one hot and one not? If the water seems to moving freely.. why the heck is one hot and one not ??!!??!!

 

[Don S]

Re: Dry Joint manifolds - ONE HOT, ONE COLD - is this ok?

No, it's not normal. When was the last time you replaced the impeller?
Alpha or Bravo drive?

 

[spunkyman]

Re: Dry Joint manifolds - ONE HOT, ONE COLD - is this ok?

Hi Don
Not sure.. it's a recent purchase. Fired it up again, but on the hose only, and seems like it's cooling ok at 150F on that left side now. But, under load, that could change back to the way it was - as that was how I first noticed - out on the water. I suppose I could pull the Alpha drive and change the impeller out just to see? Can't imagine what else it could be if I have good flow everywhere else. Even on the ears, it's coming out the bell housing/exhaust pretty good. I thought that if the impeller was shot, that little water would be coming out?

many thx

 

[spunkyman]

Re: Dry Joint manifolds - ONE HOT, ONE COLD - is this ok?

Furthermore, wouldn't the gauge go up if it was indeed overheating in the left riser?

 

[spdracr39]

Re: Dry Joint manifolds - ONE HOT, ONE COLD - is this ok?

If you don't know when the impeller was changed last I would do that first.

 

[Don S]

Re: Dry Joint manifolds - ONE HOT, ONE COLD - is this ok?

The impeller is always the FIRST thing you check on a marine engine overheat problem. All it takes is one plastic bag and you have a bad impeller.

 

[spunkyman]

Re: Dry Joint manifolds - ONE HOT, ONE COLD - is this ok?

ok.. great I will do that. One thing I mentioned that may be of help to others.... When I took off the riser, it did notice that the small hole on the metal gasket was plugged. I released that and now it's cold on the left side !!! Could this have been the issue?

 

[spunkyman]

Re: Dry Joint manifolds - ONE HOT, ONE COLD - is this ok?

To clarify, on the metal gasket in between the riser and manifold, there are 2 circular tabs. One circle completely open and one with a small hole in it (the one closest to you as you look at the engine). It was blocked on the left side, so I cleared it up and I guess it fixed it, because it seems to be working now...I just didn't think such a small blockage could impede the other fully open circle that the water travels through.

 

[frantically relaxing]

Re: Dry Joint manifolds - ONE HOT, ONE COLD - is this ok?

Furthermore, wouldn't the gauge go up if it was indeed overheating in the left riser?

NO. Water flow to the risers is independent of water flow to the engine; the risers always get a full flow of cold seawater, the engine only gets what the thermostat lets thru. And the water temp sensor is below/after the thermostat so that only the hot engine water gets measured.

 

[achris]

Re: Dry Joint manifolds - ONE HOT, ONE COLD - is this ok?

To clarify, on the metal gasket in between the riser and manifold, there are 2 circular tabs. One circle completely open and one with a small hole in it (the one closest to you as you look at the engine). It was blocked on the left side, so I cleared it up and I guess it fixed it, because it seems to be working now...I just didn't think such a small blockage could impede the other fully open circle that the water travels through.

That is a gasket, and as such once you removed the elbow that gasket should have been replaced. If it was mine (I would have done the mandatory gasket change and wouldn't be having this conversation, but) I would pull the elbows again and replace the gaskets... Make sure you replace them with the right ones (restricted flow, part #27-864850A02) and they are installed correctly (small hole towards the front of the engine, large hole to the back...

Btw, the temp gauge only monitors the water temperature as it exists the engine block (just below the thermostat), not the exhaust elbows...

Chris.........