1972 Cobalt Ski Boat

[Andy3]

I just bought a 1972 Cobalt Ski Boat, and was told the inboard was a 302. This is the first boat I have ever owned, and bought it to get closer to my daughter. The people I purchased the boat from said that the last time it was taken out, it blew a lot of white smoke and was running hot. Sounds like a head gasket to me, but having only ever dealt with cars and trucks, I wanted to get a few tips. I'm familiar with disassembly of a V-8, however, the marine set-up is alien to me. The exhaust manifolds and different hoses going everywhere. Is anyone familiar with this engine and what I have gotton myself into?

 

[Volphin]

Re: 1972 Cobalt Ski Boat

It's still the old V8 you have known... just a different exhaust setup dictating additional cooling to the manifolds. They come off like the old ones and yes, head gasket time. Have them checked and reworked while they are off. That's why I enjoy boating too. Brings you closer to your children. hmmmm. I need a bigger boat! :facepalm:

V

 

[Volphin]

Re: 1972 Cobalt Ski Boat

Oh, and replace the manifolds too. They are long overdue. Corrosion rots them from the inside.
At they very least have them tanked and pressure checked...

V

 

[haulnazz15]

Re: 1972 Cobalt Ski Boat

You likely have the Mercruiser 888 setup. The Ford 302 is like any standard Ford truck 302. You should check the oil for and "brown milkshake" substance to ensure the block is not cracked.

 

[Andy3]

Re: 1972 Cobalt Ski Boat

Oh, and replace the manifolds too. They are long overdue. Corrosion rots them from the inside.
At they very least have them tanked and pressure checked...

V

I've checked prices on the exhause manifolds and they're pretty expensive. Where do I go to have them checked? I only paid $500 for the boat and trailer. The interior was recently redone. Its an awesome looking boat and I think I got a good deal, as long as I can get a dependable engine repair going for an economical price. Thanks for the help!

 

[haulnazz15]

Re: 1972 Cobalt Ski Boat

I've checked prices on the exhause manifolds and they're pretty expensive. Where do I go to have them checked? I only paid $500 for the boat and trailer. The interior was recently redone. Its an awesome looking boat and I think I got a good deal, as long as I can get a dependable engine repair going for an economical price. Thanks for the help!

Well, you likely have what they refer to as the "log-style" manifolds which have the exhaust riser at the rear of each manifold. You can upgrade to the more modern center-riser style manifolds with a conversion kit from Osco. It's going to run about $900 either way you go, but the center risers are cheaper to replace later on, give you a slight increase in power, and free up a little bit of room at the rear of the engine.

The other good thing about the conversion kit is that is has all of the hoses, gaskets, bolts, thermostat/thermostat housing, etc to do the conversion. So not only do you spend about the same amount of money for new manifolds/risers, you also get all new hoses, clamps, and thermostat which should probably be replaced on a 1972 boat anyway.

 

[Don S]

Re: 1972 Cobalt Ski Boat

Not sure why everyone thinks it suddenly needs manifolds, or think it has a blown head gasket or anything else.

It may be nothing more than the raw water pump impeller being worn out and not pumping much water through the engine and manifolds.
at which point you get an overheat. The white smoke is probably nothing more than steam from the small amount of water going through the exhaust getting hot because there isn't enough of it.

If that boat has never seen salt water, it may not need manifolds at all.

Check and replace the raw water pump impeller first before you start throwing a bunch of un-necessary parts and labor at it.

 

[fmalott]

Re: 1972 Cobalt Ski Boat

go get them Don S i agree with the impeller

 

[Andy3]

Re: 1972 Cobalt Ski Boat

Not sure why everyone thinks it suddenly needs manifolds, or think it has a blown head gasket or anything else.

It may be nothing more than the raw water pump impeller being worn out and not pumping much water through the engine and manifolds.
at which point you get an overheat. The white smoke is probably nothing more than steam from the small amount of water going through the exhaust getting hot because there isn't enough of it.

If that boat has never seen salt water, it may not need manifolds at all.

Check and replace the raw water pump impeller first before you start throwing a bunch of un-necessary parts and labor at it.

I appreciate everyone's input. At this point it's inspection and diagnosis, and I dont want to start throwing money and parts at this thing. I've read another post on here about using acetone to detect any cracks or leaks in the manifolds once I remove them. Where is the impeller? Is it the water pump on the front of the engine?

 

[Don S]

Re: 1972 Cobalt Ski Boat

Where is the impeller?

Hard to say, have no idea what your engine looks like or what outdrive you have (or even if you have one). Some ski boats are straight inboard

 

[Andy3]

Re: 1972 Cobalt Ski Boat

Hard to say, have no idea what your engine looks like or what outdrive you have (or even if you have one). Some ski boats are straight inboard

This is a "stern" drive with a ford 302 V-8 inside the boat and the drive Assembly on the outside of the boat.

 

[Don S]

Re: 1972 Cobalt Ski Boat

The raw water pump is in the outdrive.
Have a look at this file.

 

[Andy3]

Re: 1972 Cobalt Ski Boat

The raw water pump is in the outdrive.
Have a look at this file.

Really good information. Is there anything else I should do with the outdrive while I'm back there taking stuff apart? Don't know if the boat has been in sea water or not, and not sure what has been replaced thru the years. Just dont want to get out in the middle of the lake and get stranded or worse, sink.

 

[Don S]

Re: 1972 Cobalt Ski Boat

On a boat new to you with no maintenance records, there are all sorts of things to check.
Pull the complete outdrive, check for water in the bellows, with any luck at all it should be dry in there. If there is water or brown mud, the price of repairs goes up significantly.
If dry, check the ujoints and grease if they have zirks, grease the gimbal bearing and check that it turns perfectly smooth. No roughness.
Check the engine alignment, inspect coupler splines they should not come to a sharp point, lube the coupler splines with spline grease,
Look at the water hose between the bellhousing and transom shield. If thr hose is hard, cracked or kinked, it' needs replaced, same with the ujoint bellows. I would disconnect the lower shift cable at the engine and make sure it moves fully in and out very easily, or the engine will die when shifting.
Drain the gear lube, it should not be milky, if it is, that indicates water in the drive. Might want to pressure test it before you remove the lower unit for pump repairs.

 

[Andy3]

Re: 1972 Cobalt Ski Boat

Are the hoses I encounter, a special marine grade hose or a custom molded hose, or can I use something like automotive fuel hose or heater hose?

 

[haulnazz15]

Re: 1972 Cobalt Ski Boat

The hose is standard hose, but it's usually cheaper just to buy it all in a kit.

 

[Andy3]

Re: 1972 Cobalt Ski Boat

I'm assuming the outdrive is heavy enough that I'm going to need a hoist or some kind of support before onbolting from the boat. Correct?

 

[Don S]

Re: 1972 Cobalt Ski Boat

They only weigh about 80 pounds, if you crank the bow of the boat up so the drives skeg just touches the ground, you can just slide it back. There are however, lots of home built stands if you look up in the stickies at the top of this forum.
Oh, and use the OEM hose, it's cut to the proper length, and the walls are a bit thicker than standard heater hose (less kinks), and use the natural curve of the hose to your advantage when putting it back together. You will know what that means when you get there.

Here is a link to download the manual for your engine and drive, you are going to need it.
http://www.4shared.com/document/ozc1_97A/Service_Manual_01.html

 

[Andy3]

Re: 1972 Cobalt Ski Boat

I really appreciate all your help. I'm going to start with a simple compression check of each cylinder, followed by an inspection of the exhaust manifolds and testing them with the acetone. I'll keep you updated on what I hope to be good news.

 

[Fishermark]

Re: 1972 Cobalt Ski Boat

This is a "stern" drive with a ford 302 V-8 inside the boat and the drive Assembly on the outside of the boat.

It seems to me there is still a lot of assuming going on here... unless I missed something. All the original poster has said is he has a stern drive with a Ford 302. Could it not be an OMC instead of a Mercruiser? Why assume it is a Mercruiser? (Other than being posted in the Mercruiser forum).