Starboard side riser getting really hot!! Why?

[mynameissean1234]

Hey all so I finally got my boat, it's a 97 stingray very clean with a 4.3 mercruiser and just over 400 hours on it. I did the sea trial and we were out for a while, it rain great, sounded great and didn't get that hot at all. So I bought it, took it home and the next day I went to take it out. About 3 mins into the ride I see smoke start to come out of the back seats I quickly lift the seats to look at the engine and the boot that goes from the riser to the elbow and the other boot from the elbow to Y pipe are smoking. The lower one actually ripped.

I take it out of the water and ripe the hoses apart and find out the shutter (flapper) is totally corroded and when I finish taking the boot off the Y pipe the rod for the shuttler falls in the Y pipe. I love been trying everything I can to get it out but I guess I have to take the out drive off now.

I hooked a garden hose up to the thermostat hose and water seemed to be running fine from the thermostat through the manifold to through the riser. Then I put ears on it and ran it (without the elbow on it) to see if the riser would still get hot. And it did! I got a new impeller I'm going got change it out today. Do you think that's it? I have no idea I'm lost and I'm so pissed off. First ride on the boat was only 3 mins

 

[Bt Doctur]

It got hot because no water was flowing thru it, water enters the bottom of the manifold and exits the elbow.check the hose fitting for a clog

 

[Rick Stephens]

That sucks... I can really feel for you - on first ride.

There is a silver lining, you weren't way out somewhere. But still a horrible start.


Time to go through the cooling system. Need to verify all the cooling passages are open and flowing and that the hoses were installed correctly. I would have the thermostat housing all the way apart checking for scale blocking a port. I'd be pulling the exhaust elbows off to see if their passages are clear. I would purchase an second cheap set of manifold to elbow gaskets and assembling without hooking to the Y pipe and making sure I get water flow out both sides. Not soapboxing here, I just did that, used a set of Sierra gaskets to test everything and then reassembled with OEM gaskets after test running.

Get extra outdrive gaskets. Never hesitate to pull the leg to check for or solve a problem. It is so easy, 10 minutes to come off, and prevents so many other maintenance costs.

Make sure you have water flow.

Rick

 

[mynameissean1234]

Could this be my manifolds? And or risers? I'm hoping it's just a circulation problem

 

[Rick Stephens]

Yes, it can be. You need to find what is blocked. And you need to be sure or you'll have it burn out a connector hose a lot further from the ramp. At this point, check it all out and see what is plugged up. Take lots of pictures and post them for best assistance.

Rick

 

[mynameissean1234]

I can't upload a picture for some reason. I took the risers off today to look in the manifold and it seem to be pretty rusted. There was some water in the one the manifold as well as a bunch of rust. Do you think I need to replace it? They seem to have good flow when I hook the garden hose up to the thermostat holes but I just don't know what to do at this point. I have a new water pump to put in, I'll do that first and make sure it still gets good circulation. And I'm going to make sure there's no clog in any of the hoses.The previous owner never change the manifolds or risers in the six years he had it, should I just go ahead and change them I don't want to run it any further issues?

 

[Rick Stephens]

salt water boat? or just fresh?

rust isn't the issue as much as scale flaking off and blocking something. one place that can show the corrosion is the wall thickness at the joint between manifold and elbow. often you will see that get thinned a bunch and become unsafe for your motor. a leak there can put water into your cylinders.

your problem is first to find where the blockage is. then decide whether the exhaust needs replacing.

 

[mynameissean1234]

Fresh water

salt water boat? or just fresh?

rust isn't the issue as much as scale flaking off and blocking something. one place that can show the corrosion is the wall thickness at the joint between manifold and elbow. often you will see that get thinned a bunch and become unsafe for your motor. a leak there can put water into your cylinders.

your problem is first to find where the blockage is. then decide whether the exhaust needs replacing.

 

[Rick Stephens]

Stuff lasts longer on a fresh water boat. Hopefully a gasket or something and not a rotted out manifold.