M/C 470 Waterpump/Exhaust ?

[a1nowell]

I am in the process of installing a new lower shift cable and have rebuilt my seawater pump because the plastic pipe melted and engine got hot. In removing the shift cable bellows discovered a 1/4" hole had been rubbed in the exhaust bellows by the small end clamp of the shift bellows. Would that hole have anthing to do with plastic pipe melting? Also the impeller in the pump was in good shape soft and not coming apart. I have replaced everything but having a hard time understanding why the pipe would melt when pump and impeller appear to be doing their job?

 

[dubs283]

Re: M/C 470 Waterpump/Exhaust ?

the hole in the exhuast bellows would not cause the guide tube to melt

only a lack of water exiting through the drive exhuast passage would cause that

if the engine has ever overheated or even momententarily gotten hot, that would be the cause of the melting

 

[zbnutcase]

Re: M/C 470 Waterpump/Exhaust ?

Yup see it all the time...

 

[a1nowell]

Re: M/C 470 Waterpump/Exhaust ?

I believe I have figured out what has happened. Tell me you concur.


Before the Hot problem started I started having some cavitation/ventilation problems at about 2200-2400 RPM. It has been getting progressively worse.

I read some articles today about exhaust gasses creating ventilation problems.

It makes since to me now that the hole in the exhaust bellows, which was at about 5 o'clock on the bellows and about 2/3's the way from the transom, was blowing exhaust gasses right in front of the prop and also in front of the water pick up vents. The more throttle I gave the boat the more the exhaust gas was pushed out. As this hole got progressivly bigger, the bigger my problem got.

So what do you think?

 

[NHGuy]

Re: M/C 470 Waterpump/Exhaust ?

I would think maybe, but not definitely. Here's why. Unless the through prop exhaust is blocked there would not be very much exhaust going through your bellows hole. But you absolutely ought to repair it. I hope I am wrong and I hope it solves your issue.