496HO Starboard riser rubber hose melting
 

I have been reading and searching for a couple of hours and I think I have identified the problem.

Monday a short easy run from the ramp I smell rubber burning. Stop and look the rubber hose connecting the riser to the Y pipe is smoking at the very top where it connects to the Y pipe.

Engine is slightly warmer than normal 180 degrees usually 175 degrees. No alarms.

Problem only on starboard riser.

I think I may have a stuck check ball where the water enters the exhaust manifold. I will not know for sure till this weekend when I return to the lake.

If this is the problem can I remove the check balls and run without them?

You can run without them but with all EFI / MPI engines they are their for a reason. Carb engines do not have them. The reason why EFI / MPI engines have them is after engine shut down, the motor & internal cooling water heat soak. The check valves prevent that heated water from draining back down into the cool fuel assembly / cell in which helps prevent vapor lock / fuel boiling off to help with restarting the engine(s)...

Doesn't sound like I want to run without them.

A little more info, I had my drive out for a leaking yoke seal. When I tried to reinstall I could only get the drive on to the point where the studs where flush with the drive housing. I thought it may have been an alignment issue. I borrowed an alignment tool from the guy who installed the seals in the drive and I could not get it to go in. I moved the motor up and down and it still would not go in. I moved the inner race in the gimbal and still nothing. I realized that this was an old tool that would not work with my long snout coupler after all this. I purchased a new tool and lined the motor up where I could insert the tool with two fingers and pull it out with two fingers. After all this the same thing when trying to install the drive. I guess it was just the new O rings making it hard to get the drive all the way in. I got a couple of nuts to thread and got the drive in.

I am thinking now that after moving the motor that maybe the bell on the riser is too close to the rubber hose.

I took the risers off this weekend and the bell of the riser was touching the Y pipe and this melted the hose where it was touching.

With the hose off I raised the Y pipe to make clearance, but the bell on the riser is still real close on both sides.

I was thinking about grinding 1/4" off the top of the risers or flattening the bell a little at the top. Thoughts?

I cannot improve the angle of the Y pipe, which turns down from the riser to meet the thu-hull. The Y pipes are blued a little on the top where the exhaust hits. I ordered some silicone hump hoses which will help with the heat and the bend angle.

I had the same problem, took a hammer and flattened the top of the bell to make clearance, problem solved. I suppose grinding will work also.

Scandinavian,
I actually read your thread when I was searching the site, thanks for posting. I think the flair is there to help exhaust flow a little better or it could be used to divert the cooling water to the pipe walls. I am stuck with the angle of the exhaust system so something has got to go. I think I will just take 1/4"off the top of the bell with a grinder and call it good.