'72? Mercruiser I/O leaks water, noisy, runs hot, etc. Help!

Hi. I am a first time boat owner. My brother-in-law and I picked up a 1972 Arrowglass Cheetah tri-hull with a Mercruiser 120HP I/O. It ran very smoothly for an hour or so until we realized hot water was leaking in the bilge and the engine suddenly started running loudly. We found a couple of loose hose clamps and tightened them down, which stopped the majority of the water, but there's still a hidden leak. Tried it again after a while and it runs smoothly again (still leaking), and after 20 minutes or so, starts getting noisy again. It also looks like it could overheat eventually, the needle was past the mid-point before I shut it down, but I never pushed it hard enough to find out. We are all in love with this old boat, and the leak doesn't affect our ride, but the noise is annoying, and we don't want to keep driving it around if the engine is going to get permanently damaged. Wondering if anyone knows of any potential problems I should be looking for (there are picture links below showing the engine leaking). I am an absolute beginner to boating and engines in general, but I have done some intermediate auto repairs before, so I want to take a shot at it before calling a mechanic. The other issue is I really don't know anything at all about the motor except that its a Mercruiser 120hp, so an approximate year, number of litres, etc that I could use to find a manual or parts list would be greatly appreciated. I am attaching links to detailed photos below. Any help in locating the cause of the leak, or even identifying just what kind of engine we actually have, would be greatly appreciated.
http://img829.imageshack.us/img829/8228/mercruiser1.jpg
http://img88.imageshack.us/img88/7708/mercruiser2.jpg
http://img600.imageshack.us/img600/229/mercruiser3.jpg
http://img543.imageshack.us/img543/8377/mercruiser4.jpg
http://img41.imageshack.us/img41/3734/mercruiser5.jpg

Re: '72? Mercruiser I/O leaks water, noisy, runs hot, etc. Help!

The engine you have there is a Mercruiser 120-I believe it is 2.5L. Bad news is that your leak on the block below the manifold appears to be freeze damage. The 120s and 140s (identical looking engine-slightly larger displacement) commonly crack externally right there. You might want to check your oil for water (looks milky) and see if the level is where it should be. Some folks have repaired the external crack with decent success, but if it's cracked internally (water in oil and high level), it's time to look for a new block. Good news is that a 140 (3.0) would be a direct fit replacement (similar vintage) and give you an extra 20 hp or so. Good luck.

Re: '72? Mercruiser I/O leaks water, noisy, runs hot, etc. Help!

hard to tell, may simply be a head gasket. however it should be repaired before you use the boat anymore. do a compression check, if all the cylinders check out, its most likely not a head gasket.

Re: '72? Mercruiser I/O leaks water, noisy, runs hot, etc. Help!

Alright! Thanks very much for all the info. The head gasket appears to be where the leak is coming from. We are going to tear it down soon to confirm. It has little cracks in it and seems like its petrified, so I am crossing my fingers and hoping this is the problem and not a crack in the block from freeze damage. I am hoping I will be in the market for a replacement head gasket kit. I searched online for a Mercruiser 120 2.5 head gasket and got quite a few hits from different manufacturers. They all look like mine, so I'm thinking they will all work, but I was curious if anyone knows if these kits are universal or if there are any recommended brands I should be looking for? Thanks again for all the help guys...we would still be scratching our heads right now without you!

Re: '72? Mercruiser I/O leaks water, noisy, runs hot, etc. Help!

before you by anything ,remove the manifold to confirm it is a cracked block.

Alright! Thanks very much for all the info. The head gasket appears to be where the leak is coming from. We are going to tear it down soon to confirm. It has little cracks in it and seems like its petrified, so I am crossing my

Cant check or see a head gasket untill you remove the head

Re: '72? Mercruiser I/O leaks water, noisy, runs hot, etc. Help!

Sure looks like a crack to me, if there is no water in the oil, I would try a JB Weld temporary fix,and plan on a new block in the future. As for the overheat, while the head is off I would check the thermostat to make sure it is opening at the correct temperature (pot of water on the stove and a thermometer) and pull the outdrive to change the impeller and the pump housing. While at it, grease the u-joints and driveshaft splines. Nice looking old gal. Have fun.

Re: '72? Mercruiser I/O leaks water, noisy, runs hot, etc. Help!

For sure a crack. Would not even bother with head gasket. Epoxy up the crack, and start looking for a replacement. Enjoy the boat for the summer, and repair in off time. Not point in tearing down and putting back together a junker. Or in not using the boat for the rest of the summer.

Re: '72? Mercruiser I/O leaks water, noisy, runs hot, etc. Help!

Failproof said:

For sure a crack. Would not even bother with head gasket. Epoxy up the crack, and start looking for a replacement. Enjoy the boat for the summer, and repair in off time. Not point in tearing down and putting back together a junker. Or in not using the boat for the rest of the summer.

Click to expand...

Cracked block. Need to replace the block. They can still be found in junk yards/pic-a-part. Not too expensive.