Inline 6 water jacket leak don't know what to do?!

**merc1250bayliner** · 05-17-2019, 06:40 PM

I have taken this exhaust apart 10 times now. I had the inner plate machined and it stopped leaking. I tested it by hooking a hose to the lower unit and watching it without the outer plate attached. No matter what I do I cannot get the middle baffle plate to stop leaking. The part is NLA and the machine shops I talked to will not machine it flat. It has a little bit of a warp to it and that must be what is wrong. It is not high centering on the inner plate because I have double checked that. There are no holes or cracks anywhere. I tried gasket sealer. I tried the Merc gasket dry. I tried the Merc gasket with red rtv. I am about ready to JB weld the exhaust cover to the block. I am frustrated and this is the last piece of the rebuild before I can use the boat. Any help would be appreciated.

**rock** · 05-18-2019, 06:13 AM

I am out of town right now but get ahold of me Tuesday and I will see if I have one.

Rock

**CrayzKirk** · 05-18-2019, 08:44 AM

I haven't been following the different threads. Is this a 1250/1150/1350? There was an update package available 62277A1 or later model 757781? There was a time you could call Mercury Marine and get an NLA parts search. If it's an early model, there's a new 62277 plate on eBay. I would imagine you can find a new one. The inner, baffle and outer plates have a habit of corroding away resulting in water ingestion and blowing the tops out of the bottom cylinders.

A quick search brought up Crowley Marine which offers a search of sites that may have it.

**merc1250bayliner** · 05-18-2019, 09:27 AM

This is for an 1150.

**CrayzKirk** · 05-18-2019, 09:45 AM

Post 1972? The early ones had a different inner, baffle and outer plates. Newer style exhaust?

**merc1250bayliner** · 05-18-2019, 10:18 AM

Yes it is the newer style. The plate is 75778 merc part number.

**FMP** · 05-18-2019, 01:20 PM

Originally Posted by merc1250bayliner

This is for an 1150.

Ahh yes, the one one fifty

**Robby321** · 05-18-2019, 03:28 PM

The '72 1150 is a choked down 1350 with a few flow restrictions to give the lower HP rating so Merc wouldn't have to come up with a different powerhead to fill that HP range for the consumer market. Diff exhaust tuner, but think water jackets still all the same, but dunno..have to ask my Merc Guru. Post this on Fiberglassics, in the Merc forum, lots info on the notorious jacket leaks!

**CrayzKirk** · 05-19-2019, 08:03 AM

There are some used ones on eBay. I would go with the new route with one addition, move up to the 1500. You will be much happier.

**merc1250bayliner** · 05-20-2019, 09:07 PM

I tried a double gasket today with no luck. After that I filled down the high spots around the bolt holes and reinstalled the gasket with RTV on both sides. I will see tomorrow what happens but I am not very optimistic. Obviously this thing has to be perfect. I am going to have to find a NOS new plate or a machine shop that will do it. Not looking good either way.

**Robby321** · 05-20-2019, 09:26 PM

Pix would help here..

**rock** · 05-21-2019, 07:44 AM

Hope the ebay thing works out. I looked in the shop yesterday when I got home and I do not have any inline blocks left. Sorry.

Rock

**Motv18** · 05-21-2019, 07:51 AM

It’s tricky but a good weld shop can rebuild the mating surface. Which you can then mill.

Welder needs to be good at weld filling holes to not warp it more.

Thats more of a last grasp thing.

**merc1250bayliner** · 05-22-2019, 05:25 AM

I am going to try and make a spacer plate to have a flat or flatter surface to bolt to. My only question is how will the performance or reliability of the engine be effected if the baffles themselves are spaced a 1/4" apart from each other?

**Dave S** · 05-22-2019, 09:44 AM

Ya chaseing ya tail.... I have plates........A guy I know had same probs..... never could find the leak... took a torch to it and when hot the crack opened up.......I will check with my stock.....pile