Hi Guys

the thing that makes me struggle a lot is the o-rings at the manifold. they seem to blow out after a run or 2 and I am contemplating if I should use high temp silicon instead (again not ideal).

I tried silicone, teflon and other high temp materials available.

Cheers
Andre

What kind of flange is it? Some are just plain bad. I've had some that would continuously burn the Orings no matter what I did. I now use "no-leak" style flanges with great success. I highly recommend them.

Address these two points and likely your o-ring troubles will be less ...

#1 ... limit the side to side and forward back movement of entire pipe. As boat corners the g-force side swings the pipe causing it to try and pivot on the manifolds o-rings. Too soft of motor mounts also cause excessive movement at manifold. * Pipe needs to move with engine and it's own vibration, but should not be held firmly simply by the couplers o-rings either.

#2 ... Round off the OUTSIDE edge of head pipes flange. A square sharp edge as they come cuts the o-rings very quickly. File a bevel on both corners, then sand the edge into a nice rounded profile.

Try it, you will like it .....

Thanks for the tips. I think both apply.... I tried several manifolds and I will give the No-Leak ones a try next. I will also work on the tips of edges and pipe mounting. I have started to make the pipe rigid in regards to the connection to the engine and allow enought movement to move as one unit with the engine.

I have also trouble finding the right size O-ring as inner and out diameter need to be of precise measurements and ususally one or the other is not .

I will incorporate your tips and hopefully make the blown O-ring saga a thing of the past.

cheers
Andre

cc racing no leek .... ill never use enny thing els.
im new to r/c boats and had that problem , and now all i do is replce the orings on the no leek when pulling out the motor . and so far have not realy had to replce them .i use the viton oring i think a pack of 10or?is $5.
i have a frend with a rmck that has had no end of problems . and he blows out the seals on nearly every run. and that is with the origanal rmck rear exaust manifold.

good orings i think also help...

happy boating to youB) .

Final issue , tho hard to do anything about.

The DIAMETER of the head pipe flange, Larger the diameter the more it's compressing the body of the o-ring and not just the side of ring that cause it to be cut into like smaller diameter flanges will do.

Tell your friend to check the alignment between the engine and the pipe. If his pipe support on the back of the boat puts a bind on the pipe, the the O-RINGS will certainly burn out.

I found this topic interesting because if an otherwise faultless boat has to stop because of blown O rings it is very frustrating.

I now only use the Viton O rings as I understand they can cope with higher temps than the silicon ones.

The thing I find critical is to ensure that the rings seat properly once the flange is tightened up. With some flanges it is very easy to crimp or trap the O ring upon tightening the flange bolts. And it can be difficult to spot.

One obvious test is to blow air into the water cooling jacket and ensure that it is air tight.

One other thing I do is to smear a little oil on the O rings prior to fitting them. I find that this helps them pop into their retaining grooves.

The point made previously about ensuring accurate exhaust alignment is I think especially important.

In the photo below my exhaust requires no movement in order to connect the single rubber mount (shielded with the horizontal alloy sleeve) to the support strut. I positioned & installed the support strut with the exhaust system all in situ to ensure that all components mated together naturally. So far this has given me zero failures (famous last words!).

A couple things I found
I use the thicker STOCK exhaust gasket - I burned lots out with copper and with just using sealer - I burn a lot less when thick stock exhaust gasket is used

I also found China o rings seem to burn up faster

A good fit is a must and limit movement with out making it totally solid

if I use grease I use high temp

just my 2 cents worth

no one seems to have mentioned your motor maybe running to lean.