Mariner 30 | Inlet manifold

[HughN]

I have one of the old ex-contract Yamaha-built Mariner 30's that (apart from the outside) is generally in good nick and has always run well.

Recently , however, been a blighter to start and when I was trying to start it with the cowling off I spotted an occasional blast of air/fuel exiting at high speed from where the inlet manifold meets the block (i.e., behind the reeds).

Cursing the person who serviced it, I tightened all of the screws from their 'quite loose' state and it now starts on the merest turn of the key. One of the screws/bolts is more-or-less stripped though.

How much pressure does this experience when the engine is running? Not as much as is exerted on the cylinder head, but anything that should be giving me sleepless nights knowing one of the bolts (one of about 10) is not 100% tight?

I suppose I could take it apart again and use some Hylomar Blue...

[Nos4r2]

Don't use blue Hylomar on it-it's prone to squeezing out and dropping bits.You don't want it going through the motor.
Use red if you need to. Better to helicoil/replace the bolt though.

As for what pressure it's under, absolute max of 1 bar, or 14.5psi-from outside air pressure.

[Bombardc2]

+1 for a helicoil. You won't have pressure but there will be vacuum in the manifold

[Nos4r2]

Originally Posted by Bombardc2

You won't have pressure but there will be vacuum in the manifold

Which is what I said in a roundabout way

[HughN]

Thanks