MerCruiser 7.4L Bluewater Exhaust

[Bondo]

Thanks Bondo, but it's not the bolt you can see it's the one on the manifold to the head that you can not see. The elbow to manifold joint was leaking right at bolt the arrow is pointing to and ran down and corroded manifold bolt. I do not think the bolt is frozen in the threads as all others came out clean. Just can get a bite on the bolt head. I ordered some extracting sockets for stripped bolt heads they will be here later.

Headed there in a few minuets with an arsenal of tools, with any luck it will be off before lunch. I will post an update later.

Mike

Ok,..... Then cutting the head off, isn't an option, unless you pull the motor 1st,.....
If the head is cut off, the manifold still won't have enough space to slide of the remainder of the bolt,.....
It looks to be so tight, that weldin' a nut to the bolt head is also impossible,....

Good Luck,...... yer gonna need it,......

 

[Scott Danforth]

you can cut the head off then slide the manifold outward about 2", and then cut the bolt about 3/4" away from the head. then when the manifold is out, weld a nut to the bit left and unthread.

 

[mr300z87]

Well I had some success yesterday although not exactly what I planned. Although I was unable to remove the bolt I am struggling with I did remove the Port engine center manifold which gives me much more room to work.

Note there would have been enough room to slide it off the cut bolt even with the port manifold still on, just no way to get near the bolt to cut the head off. Next up to try are stripped bolt head sockets, I just don't want to snap it off, but as you can see the bolts I threaded back in on the port head are nice a clean. Unfortunately there are 2 other stripped bolts on the outer manifold of port engine but they are slightly more accessible to get at with the cut off wheel. I was able to get my head and hands down between the engines if I need to cut. I did speak to the marina yesterday and my last resort if I will be calling them to deal with last 3 bolts. All in all 3 out of 32 is not a bad ratio. Their mechanic has to be a lot younger then I AM.

The good news is I have all the parts to put it back together except for new plugs which I am thinking would be good to do now with easy access. BTW that cookie tray fits perfectly between the engines to catch tools and bolts that might get dropped into the abyss.

 

[mr300z87]

When I took the old Manifold out of my truck I noticed what looks like a date code next to the casting number 1F97.

Is is possible these manifolds are 25 years old? They are part of the closed cooling?

 

[mr300z87]

SUCCESS!!!!! All bolts are either out or loose, I have not removed outer manifold on port motor yet but since all the bolts have been loosened that is an easy task to remove and replace. These fluted sockets worked great grabbing the stripped bolt heads.


Once I had both center manifold off i was able to remove the raw water pump for replacement. This was a joy, not sure how it could be done without removing the manifold. The only way to do this job was to disconnect the intake from the stainer and output hose from the trans/oil cooler and remove the pump with the hoses. I needed to stand be the engines to get at the bottom of the cooler to remove the hose.

I also chased all the enter exhaust manifold threads on both engines with a tap to make sure the new bolts go in good. I'll do the outer ones before install. Then I said I'm tired and decided to head home. Tomorrow I will do the water pump and start prepping the new manifolds and elbows on the workbench at home.

Any recommendations of what to use to clean 30 years of nasty from the bilge? Water should be on soon and I want to clean before re install.

Have a great rest of the weekend.

 

[mr300z87]

Yesterday after work I ran to the boat to re-install the raw/sea water pump, while I was doing so I noticed the hose going from the circulating water pump to the heat exchanger was leaking AF. A quick seach on the internet reveals this hose and the following generation 7.4L hose is NLA. There was 1 NOS on ebay that I bought $125 and it is supposed to be here early next week. This will delay putting the new center manifolds on since I could never get to this hose if they were.
I am sure I am not the only one ever to need this hose. What have others done, there are a lot of 7.4L out there. The hose goes from the front of the engine circulating pump to the back where the heat exchanger is. and has 2 90 degree bends.

It is leaking right at the water pump I was thinking if I bought the lower radiator hose from a similar vintage Chevy 350 BB truck and I could splice together with a 1 1/2 in coupler and some clamps.

Nothing is easy when working on a 32 year old boat.

 

[mr300z87]

Over the last couple day since the weather started cooperating I have completed installing the exhaust and refilled the closed cooling systems with coolant. All that is left is to connect the 2 center exhaust tubes and re mount the coolant over flow tanks. Both were in the way of re doing the blowers and vent tubes.
Today I had to go back to working so the boat now has to wait until the weekend, my plan is to do an engine run now that we have water on at the marina. The with the coat of paint my wife and I did this past Saturday, I will call her ready for launch. Once she is tied up at the slip I will take care the basics oil change, fuel filters, check timing and a good cleaning. I did the plugs while the exhaust was off just because it was easy.