One exhaust manifold running hotter?
 

The ol girl has had fuel and water pumps replaced and the mechanic was doing water test and said he noticed one side was running hotter on the manifold. He took them off to check for obstructions I guess? He now mentioned pulling the heads to investigate further. I don't know how much hotter it was running. Does this seem necessary?

Re: One exhaust manifold running hotter?
 

Not to me.
I think I would be doing a lot of other things before I tore the topend down.
Find out what was the dif in the temp readings? Sounds like more of a cooling blockage issue to me.
Did he do a compression test to make sure there wasn't a dead cylinder?
Ask him why he wants to pull the heads? Make him explain to you the "reason" for doing this , before investigating the cooling system further.
This is just my opinion Patrick , but that sounds very fishy to me to jump from a heating issue on the manifolds to tearing down the motor in one single swoop. :(

Re: One exhaust manifold running hotter?
 

I was thinking how you are, about blockage in cooling system. I looked in my notes I jotted down and he said the difference was 200-300 degrees difference. That seems like a big deal to me. Anyway I'm taking a trip up there tomorrow morning to talk with the mechanic so ill keep you posted.

Re: One exhaust manifold running hotter?
 

Also was this done while running the boat on a hose or while running in the water? Sometimes one will run hotter than the other especially while idling. I would make sure to run it up to temp not just on the hose or at idle and recheck.

Re: One exhaust manifold running hotter?
 

200-300 degrees is a meltdown difference in temperature. My boat always rund around 180. I know I've had cars with v8's that overheated (ran above 240) and would not run. I'm wondering how that boat would run with a difference like that. I know the manifolds will run hotter than the temperature of the block but OMG!

Re: One exhaust manifold running hotter?
 

He said the temps are the same on the heads. It was out on the water for the test. I really don't see how the heads could be the same but manifolds be so far apart.

Re: One exhaust manifold running hotter?
 

If the heads are running at the same temp , the only thing that can being "heating up" the manifold is a blockage.
You got flaked off rust or something blocking a passage in the manifold itself , or a exhaust flapper broke off and wedged , or something to that effect.
I can not see a 200-300 deg diff even if a manifold is plugged. You would be melting boots!!

I would be real leary of letting this "mechanic" work on her. You know....it's like going to the doctors , sometimes you got to get a second opinion. :)

Re: One exhaust manifold running hotter?
 

Oh Boy here we go. How to explain and be understood. If he (the mechanic) is taking the temps from the exhaust man. then you are seeing exhaust temps (from those big explosions that push our boats forward) or the coolant side (of an intake man.) you would possibly be looking at the spread of temp on say coolant intake from radiator to engine as opposed to the exhaust side of the coolant temp after circulating through the engine then out to the radiator then back to the engine or as in a boat it is in and out.
Some engines will run hotter on one side than another. I would not be alarmed at this point unless you had the pumps replaced due to temperature or overheating issues. How is the mechanic coming up with the other temps with a actual sending unit placed in the system or a heat gun? I would not rush to have the heads pulled on that information

Re: One exhaust manifold running hotter?
 

Why question is did he take of the manifolds and rises before he told you he wanted to take the top end apart, risers and manifolds are known to get clogged up

Re: One exhaust manifold running hotter?
 

He took off manifolds and said there was no blockage. I'm starting to think that I'll just run it how it is.

Re: One exhaust manifold running hotter?
 

Ive had plenty of boats, not saying i think i know whats wrong but, my thought is its unusual for there to be a problem with the engine if its running fine with no sign of miss fires.

Do you have captains call on it.

Re: One exhaust manifold running hotter?
 

Yes it has captains call. Would one of the flaps staying closed cause that bank to run hot?

Edit: just left marina talking to the tech. The port exhaust manifold runs 160 on the water, starboard hits 220. Which explains why it vapor locks since thats the side the fuel line runs. He was looking through mercruiser service bulletins and found one that pertains for us. It said with 3" manifold risers, captains choice should not be installed...guess what this boat has installed. Yep you guessed it. Anyway I think we are making ground. He also found a loose ground fitting on the battery ground cable, had it taken off and was still getting power on the dash. He pointed out some wires running to the ECM that were melted from the starboard manifold also. This thing is a mess. I hate what previous careless owners do!

Re: One exhaust manifold running hotter?
 

All the flap for the capts call does is divert the exhaust , it doesn't close off the flow.
If you had a solenoid not working and one was open to thru hull and one was open to prop , you'd know it.

Re: One exhaust manifold running hotter?
 

More bad news. Sounds like the hot side had a bad head gasket. Going to have both sides done. Maybe will have this up and running before summer is over.

Re: One exhaust manifold running hotter?
 

cool and good luck its an intensive job when doing it on a boat.

Re: One exhaust manifold running hotter?
 

Update: got the boat back yesterday and she runs better than it has since I've owned it. Ended up replacing head gaskets, distributor cap was worn, captains choice exhaust was rotted out inside bilge, pieces of former impellers was blocking the oil cooler, replaced sea water pump and fuel pump, and fixed some burnt wires going to the ECM. The tech said inside the rotor cap there was actually mold. Yuck. I couldn't believe how good she ran, we are figuring out the previous owner(s) did not care much for maintenance. Hopefully no more getting towed in. But remember, a bad day on the lake is still better than the best day at work.

On a side note I finally decided on a name. liquid asset

http://i58.photobucket.com/albums/g2...ps33bc3b9b.jpg
http://i58.photobucket.com/albums/g2...psf42bc3c1.jpg
http://i58.photobucket.com/albums/g2...psa3451725.jpg