1987 Carver 3697 filler neck and overheat

[carver3697'87]

Hello all! I have had a good season with the boat and took it for one last ride during the week. On the way back from the restaurant the port engine overheated. Upon returning and inspecting I found both plastic manifold elbow/drains had blown out. I scraped out the remaining plastic threads and installed new elbows. I noticed when I went to fill the cooling system the cap was loose and the brass housing was bent. A lot of pressure built up for sure. The filler cap housing is round on one side for the hose, then the cap in the center, then a flat square surface with four bolts. I need to know where to source this part! Also, how much coolant should the boat take, and yes I need to find out why it over heated, and it does it really fast when it does.. maybe head gasket, maybe a stuck thermostat..that engine had been getting harder to start possibly unrelated. what causes those elbows to both blow out of the manifolds, they probably melted from the heat first. Thanks1

[Viper]

It would help if you posted engine info; make, model, serial number.

[km1125]

Also post some pictures of the parts you're trying to describe. Much easier to relate it to other models that have similar parts.

If you think there was enough pressure to cause physical damage, then you should test and/or replace the cap. They should release any pressure that gets over about 15 PSI.

When did the actual overheat happen? Was it up at cruise or after a cruise? How long do you think it was actually HOT before it overheated? Did you get any alarms?