Mecruiser 470 Help

[jbuchholtz1]

I need some advice on a 1984 Mercruiser 470. I pulled this boat out of a barn. It hasn't ran since 2005. I was told the heat exchanger was cracked. It appeared there wasn't any antifreeze in it because I could not see any in the reservoir when I took off the cap. I pulled the riser off and found that the exhausted chamber on the stern side of the manifold was full of antifreeze and there is a crack between the front and rear exhaust chambers of the manifold. there was also antifreeze in # 4 cylinder. Compression is between 155-165 all cylinders. I did order a new exhaust manifold but am not convinced this is the problem. The research I have done so far indicates a cracked manifold but the only thing on either side of the crack seems to be exhaust chambers not water jackets. There isn't any water in the oil. I don't want to waste all this time fixing it if there could be more to it. The heat exchanger was replaced a few years back and still looks brand new. 100% checks out as being good no cracks. Any advice would help.

 

[guyjg]

The 470 is Merc's "red headed stepchild". A great idea but was plagued w/problems. Since the compression is decent you might get lucky and only need a new manifold. Antifreeze in # 4 cylinder but none in the oil? When you install the new manifold pressure test the cooling system. If it holds pressure it could be ready to fire. Install a new set of points and condenser if the old set looks aged or fried. If there isn't an alternator installed then it still has the OB stator charging system. Make sure the charging system is working. If it isn't then get an alternator kit for it and remove the stator system. Alt. kit is cheaper than fixing the stator system. You'll also want to install a new impeller in the LU. Make sure the thermostat is working properly. GOOD LUCK!

 

[jbuchholtz1]

Thanks guyij. I also found it strange not to have water in the oil. I have yet to drain it which is on my list of things to do today. Could be since oil floats on water it doesn't show on dip stick but even so oil looks clean as the day it was new. I have heard good and bad things about the 470. The charging system being the bad. Thanks again for the tips.