Exhaust gasket 90hp sport jet

[Marks Rayder]

I recently bought a 1994 Sea Rayder 90hp I have used the forums to get it running (no spark) thanks to all for there great advice on other posts. I have an exhaust leak I replaced the exhaust gasket with Black RTV Ultra still leaking. My question is should I use RTV or just dry? Is there a torque pattern and what is the torque specs on it. The cast surface does not appear to be very smooth. It also has 4 or 5 stripped bolts I am working on retapping them and putting in helacoils. Any thing on that may help as well.

 

[Frank Acampora]

No need to use heli-coils. There is not a lot of metal on the bolt bosses and seal will be problematic. You can, however, drill deeper, tap 1/4 - 20, and use longer bolts. Black RTV or any RTV is simply not enough to properly seal. You must use a gasket. If they are NLA, use 1/32 grey gasket paper and make your own.

Torque bolts to 70 inch pounds in a spiral pattern from the center outward.

 

[Marks Rayder]

Thanks for the help. I did have a new gasket with the rtv. The gaskets are still available I have one on order now. How deep should I drill to tap the holes out? Do I place the new gasket with or without rtv? Getting ready to swap bent ride plate too. Lol learning a lot very quickly about this old jet boat.

 

[Frank Acampora]

Once you take off the exhaust cover--in your case, different than the outboard-- you can see that the bolt bosses run all the way to the cylinders. So, you can go as deep as you want. In reality, there is no need to drill and tap more than 1/2 inch deeper than original. The original gaskets are designed with a "glue" on one surface and after tightening and running, this sticks the gasket to the surface. The manufacturer never used any sealant but I suppose that using RTV or Permatex is optional depending upon how it makes you feel. If you used RTV plus the gasket, there certainly should have been no leaking. So before assembling everything, check for warping on both mating surfaces.

 

[Marks Rayder]

I think that the leaks where because of the stripped out bolts. I did not realize that there were five stripped out bolts, some had heli-coils. I am going to drill them out as you instructed. The surfaces don't seem to have any warping but there are a few spots that look like there is a small gap on the aft side of the engine. I will post a picture to see what you think.

 

[Marks Rayder]

Here are some pics. When you put a straight edge up to it there is a gap in those 2 spots. Roughly a 1/6th of an inch.