Fiberglass exhaust tube is hot on port side - only

[JayG80]

Boat is a 2002 Ski Nautique powered by a PCM GT-40 and has 570 fresh-water hours. Just replaced the riser manifold gaskets and while testing for leaks I noticed that the risers were the same temperature and mild to touch. The port fiberglass exhaust tube was much hotter than the other. Boat temp gauge is normal 140*. Boat runs fine.

Removed the port riser and confirmed the gasket was installed with aft port blocked by the gasket. Riser does not show abnormal signs of corrosion. Put on another new gasket.

Boat was due for new belts and impeller. Replaced them and impeller was intact.

Recently, there has been a 1/4 cup of water in bilge after 1 hour use. I found a pin hole leak on starboard side of muffler and patched it with epoxy stick.

Pulled the thermostat and replaced with 160 degree PCM part. Ran garden hose on port side hose out of thermostat housing and had good flow to stern flapper.

Borrowed a point and shoot IR thermometer. Ran boat at idle for 30 minutes, dash gauge read 140*, IR read 110* on each iron riser, Starboard Fiberglass tube was 120* and Port tube was 190 -200 degrees while engine gauge showed 140.

Do I have an issue or am I overly concerned. For comparison, I'll check the fiberglass exhaust tube temps on a 2006 Ski Nautique tomorrow.

How hot is OK for the fiberglass tubes? Could I have a muffler issue creating back pressure and higher temps?

[JayG80]

Will try some steps suggested in this thread. http://www.planetnautique.com/vb3/sh...nk-overheating

I have also tightened all hose clamps and cleaned the sea strainer. No leaks are evident. Every time I change the impeller it has been 100% intact.

[Mikeski]

I would guess there are some pieces of an old impeller blocking water flow to the port exhaust manifold. Pull the cooling water hose and check the brass elbow where the water enters the manifold.

[bchesley]

You could also have a hose that has come apart form the inside and there is a flap of rubber preventing water flow. From the outside it will look fine. Go from start to finish of each hose and squeeze to see if there is a weak spot.

Brad

PS. Even an exhaust hose can cause this.

[JayG80]

Thanks guys, good tip on squeezing the hoses.

I have never had an impeller lose a single fin. Boat is running great and gauge is showing around 140. Fiberglass tubes were 150 starboard and 170 port today. Water is cooler than a few days ago. I pulled the hose from strainer to tranny cooler and it was clear. I shot a garden hose in it to flush out just in case.

Will pull the hose leading to the brass fitting on exhaust manifold. I tried to get it off the other day and it was pretty stubborn. I did run garden hose through its other end and flushed it out to exhaust flapper. After that I'll just keep an eye on temp gauge and hope nothing catastrophic happens.

[Bri93SN]

There could be an internal blockage in the muffler, causing back pressure. It sounds like the muffler is starting to fail if you saw a leak.

[DanielC]

This is a thread about a flushing adapter I made.
http://www.planetnautique.com/vb3/sh...ushing+adapter
One of the ways you can use my flushing adapter is to pressurize the raw water system between the raw water pump, and the intake hose, at the through hull fitting, if you remove the water intake hose there. This allows you to check for air leaks in any of the hoses, transmission cooler connections, and raw water strainer connections.

Once you have confirmed no leaks, get a long enough piece of 1 1/4 hose and hook it to the intake of the raw water pump. Put the other end of the hose in to a five gallon bucket, but not on the bottom of the bucket, or cut that end of the hose at an angle.
At 3000 RPM, the raw water pump should be able to drain the five gallon bucket in 15 seconds, I am told. If it takes significantly longer, you may meed to repair or replace something with the raw water pump.

[MTRBTR]

JayG80 did you ever get to the bottom of this? I seem to have the exact same problem today. Water pumps fine engine runs cool, but exhaust tube on port side is hot. Water in the manifold. Im going to tear into it now and see what I find.

[JayG80]

I think Bri93SN was correct in his post about the muffler starting to go. I never resolved it for 2 years until I replaced the muffler. The heat levels lowered but never equaled. I think the temps equalized when the muffler's internal wall detached and allowed water to flow a bit better. The muffler would pillow up when engine reved. I'm not sure how long that happened, I never ran the boat with the muffler exposed until I started looking for a rattle in the muffler. See my post on loss of hole shot.

http://www.planetnautique.com/vb5/fo...lls-horsepower