Fixing leaking exhaust plate on 1972 1150

[bunker108]

I have been on the hunt to repower my boat due to a leaking exhaust plate causing cylinders 3 & 4 not to fire once warmed up to temp. After looking at several used Mercs much worse off than mine I think I might just try to repair this one.

For anyone who has attempted this repair, what are the odds off sucess and what parts are needed? It appears that there is a gasket there...and I have read that the plate will need to be machined to level or replace if cracked. Any other suggestions...?

Thanks!

 

[meggy73123]

Re: Fixing leaking exhaust plate on 1972 1150

did mine over the winter took a couple of hours I didn't machine anything and the gasket as cheap,

 

[chum1]

Re: Fixing leaking exhaust plate on 1972 1150

First concern for me would be snapping off bolt heads, if its a 72 model that may be a real possibility..... then its easy out time after removing powerhead with lifting ring http://www.amazon.com/Mercury-Mariner-Outboard-Motor-91-90455-1/dp/B005CWC3CO to lay flat on bench (with powerhead off might as well replace lower crank seals), the exhaust plate will probably be very easy to find new or used (if old one is cracked throw it away), fairly easy process after that with cleaning/installing parts with new bolts/gaskets and orings per manual.

Are you sure 3-4 cyl has water problems? plugs will looked steam cleaned.

 

[bunker108]

Re: Fixing leaking exhaust plate on 1972 1150

The plugs on 3 & 4 were steam cleaned but the pistons on 3 & 4 were not, but 3 was cleaner than 4. 3 and 6 were the "cleanest" but this engine is all carboned up.

Pictures to follow.

 

[bunker108]

Re: Fixing leaking exhaust plate on 1972 1150

Here are the ghosts I am chasing.
Struggling to get on plane and acts like it is dropping cylinders
If I do get on plane I am can spin 5K...I used to spin 6K

 

[bunker108]

Re: Fixing leaking exhaust plate on 1972 1150

What do the experts think?

Thanks!

 

[chum1]

Re: Fixing leaking exhaust plate on 1972 1150

Congrats went through the same thing a few years back here is a couple of my old threads that may help:

http://forums.iboats.com/showthread.php?t=394962

http://forums.iboats.com/showthread.php?t=419118&p=2798618#post2798618

 

[bunker108]

Re: Fixing leaking exhaust plate on 1972 1150

Ok so at this point I need five gaskets right?

1. the spark plug side water gasket
2. The exhaust plate gasket
3. The exhaust plate to block gasket
4. The inner exhaust gasket
5. The lower power head gasket?

What am I missing and does anyone know part #'s? I need to get these ordered asap!

SN# 3367838

 

[bunker108]

Re: Fixing leaking exhaust plate on 1972 1150

I have spent a little while this evening going at the broken off bolts, after a soaking of PB blaster, with a torch. I am not having any luck and have managed to snap the remnants of three more broken bolts. I will try again tomorrow but I am afraid these will need to be drilled out.

 

[bunker108]

Re: Fixing leaking exhaust plate on 1972 1150

I am going to order a gasket set to get this thing back together.

Sierra part # 18-4356 is the only set I can come up with but the serial number starts at 35.....and by serial number is 336....

Can anyone verify this is the right set?

 

[redjmp]

Re: Fixing leaking exhaust plate on 1972 1150

I just did this job on my 86 115 about a month ago.
I snapped a couple of bolts off myself but was able to get them out with lots of heat and pb blaster and a little drilling...
These are resiwelded in place I was told and need lots of heat to melt the resin.
Mine didn't look like it had as much corrosion as yours but new gaskets fixed my leaky #4.
That part number is for the whole gasket set but you should only need 4.
I paid about $30 for all of them.
You should not need the water cover gasket where the plugs go in just the others you listed.
18-2573, 18-2574, 18-2835, 18-2839

 

[bunker108]

Re: Fixing leaking exhaust plate on 1972 1150

Thanks red! I did pull the water cover on the spark plug side so I will need that one too. That was the worst one and the only one that I sheared bolts off of.

I got all the broken bolts drilled out. I am glad that the block is not threaded and the holes are backed up with nuts, so at least I will not have to heli-coil anything. I spent most of the afternoon tackling the broken bolts and cleaning the gasket surfaces. Everything is now pretty clean and I will onlt need to do final surface prep to get ready for things to go back together. I will order gaskets tonight and I hope to have the powerhead back together by next weekend.


Could I have been losing compression due to leaky water seals?

 

[bunker108]

Re: Fixing leaking exhaust plate on 1972 1150

I got most of the gasket surfaces prepped. There is some minor pitting that I am not going to worry about as they appear to be on non-sealing surfaces. Except for the inner baffle which has some pitting between to ports...it is not terrible but concerning. I don't think it will be difficult to get it sealed...at least I hope.

 

[chum1]

Re: Fixing leaking exhaust plate on 1972 1150

looks pretty good to me, you might lay a straight edge on the sealing surfaces and make sure everything is straight also now would be a good time to replace the lower crank seals since everything is apart, i think 3 bolts to remove and the cap to pull.....kind of cumbersome but very doable.......your girlfriend/wife will be happy u did when shes getting pulled around in a tube.

 

[bunker108]

Re: Fixing leaking exhaust plate on 1972 1150

My gaskets should be here tomorrow. Today I am going to get new nuts and bolts to go back together with. What sealant should I use on the outer plates and what should I use in the inner bolts and inner plate. I have read many different options. What has anyone here used with the best success?

 

[bunker108]

Re: Fixing leaking exhaust plate on 1972 1150

I ordered the wrong gasket set. I ordered 18-4356 when I needed 27-55284A1. Those should be here tomorrow. The bad thing is I go back on shift tomorrow and don't get off until Wednesday morning...when we are supposed to be leaving to the lake! I still might be able to pull this off but we will see.

 

[bunker108]

Re: Fixing leaking exhaust plate on 1972 1150

I got everything back together and fired up. Seems to be running good and hitting on all cylinders. But....now I broke something on the shift linkage in the lower unit. The shift shaft just spins now...so the saga continues.

 

[redjmp]

Re: Fixing leaking exhaust plate on 1972 1150

I got everything back together and fired up. Seems to be running good and hitting on all cylinders. But....now I broke something on the shift linkage in the lower unit. The shift shaft just spins now...so the saga continues.

If it doesn't shift, chances are good that you didn't have the shifter and the lower unit aligned when it went together.
Pull off the lower unit and manually set it to neutral. You will feel a detent and the prop will spin freely.
Put the shifter in neutral as well before putting it back together...

 

[bunker108]

Re: Fixing leaking exhaust plate on 1972 1150

The mistake I made was not dropping the LU when I installed the powerhead. During the powerhead instalation I must have hit the shift linkage and knowcked it out of alignment. So I had the typical FWD and no REV. So I dropped the LU, lined it all up and reinstalled...it took me about 6 attempts to get it right.

So I fired it up on the muffs, let it idle a bit and engaged FWD...all good, and when I pulled back to reverse it was out of adjustment and wouldn't enagage all the way, just grind. So I adjusted the cable and tested again...this time something broke. I dropped the LU again and found the splined shift shaft just spins. It doesn't shift anything and the LU is in FWD. So that splined shaft that sticks up from the LU must have come free from the shaft or the shaft free of the shift cam. Either way I don't really want to tear it apart and would rather find a replacement LU. PM me if you have one.

 

[chum1]

Re: Fixing leaking exhaust plate on 1972 1150

thats a bummer, there is a circlip that keeps that shaft from pulling out it hits on a seal assy. housing that screws into the lower unit, it might have been missing or rusted away. If the lower end is not totally shot and still good i would reseal it and reset that cam, maybe even put the easy shift 44532A 1 Cam Follower Kit in it, learned that from fazt and it does make a big difference in the shifting. I have read switching around lower ends with different gear ratios will affect pulling power out of the hole no matter what prop you put on.