455 olds freeze plugs?

[big dave]

i have a 20ft 75 kona with 455 and jg berkley pump. my problem is. while out on the river last year. i noticed water blowing out under the engine. i assumed i'd gotten a hole in one of the crossover hoses. i limped to the dock and went home. now i go to start the boat turn on the hose and water is pouring out of the block. closer inspection reveals three freeze plugs blown out.i had problems with blown intake manifold gaskets when i first got the boat. some crossover blockoff plugs fixed that problem? so is there a buildup of excess pressure that is causing these problems. thanx dave

[Taylorman]

The freeze plug probably rusted through and has a small hole in it. Pull it out and replace with a brass one. Or and easier fix is to go get a rubber expanding plug.

[victorfb]

first off, were do you live? does the boat sit in an area were the water in the block can freeze during the winter months? they may have been pooped out some by this and you are just noticing it now after the water preasure forced them the rest of the way loose.
install a guage on the water system. somewere you can read it while running at speeds. have someone watch it and take a reading. with 3 plugs popping out im betting its more than just a rusted out freeze plug. 3 at the same time would be a very uncommon coinsidence. and with having prior water leakage problems id be concerned. your block preasure shouldnt be much higher than 20-25 pounds at high rpms. the lower the better but dont sacrifice cooling.

[big dave]

i live in portland Or. it does get below freezing during the winter. i'm going to pull the motor and check it out.should i be worried about block cracking.or did the freeze plugs prevent that ? thanx dave

[victorfb]

in extreme cases the block can crack but doubtfull. thats what the freeze plugs are designed to prevent. hense the name. seeing that yours were popped out in multiple areas id replace all of them and with brass to prevent corrosion. an inexpensive tool can check your water sytem by preasurizing it and looking for leakdown. most any good mechanics shop will have one aswell if you want to bring the boat to them. on a lighter note, atleast this is a good time to try and wash out any sand or sediment that has accumulated in the water passeges of the block. typically around the cylinders. installing a petcock on the block will allow you to drain the water from the block during the storage of the boat in the off season. refilling with antifreeze will also help prevent corrosion.

[Moneypitt]

Do not use rubber expandable plugs in place of real freeze plugs in a jet boat unless you are tired of it, and it's well insured against sinking...........MP