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Mariner 40B power head job, 1978 Mariner 40BE 676

H. I. McDunnough

Regular Contributor
I have a 1978 Mariner 40BE 676 that I am trying to put in service. When I first bought it, I had a mechanic look it over. He said it had good compression, but that the plugs were wet. He put new head and cover gaskets on it. I later noticed that they were wet again. He replaced them again, and then, I retorqued it again at the begining of this season.I notice that now my bottom plug is wet. It has been sudgested to me that it is the exhaust cover that is leaking. This is all new to me; I've never messed with such things, but I've done so much to this motor that I'm pretty familiar with it. I'm going to replace the exhaust cover gasket. I'm also planning on replacing the exhaust plate gasket at the bottom of the power head. I noticed some water spray on the intake manifold and the exhaust plate gasket looks like a more likely suspect. I'm ready to order the gaskets. I'm just not sure if it's every thing I need, if I should use gasket sealer, ect., or if I should put never-sieze on the bolts. Well, most importantly, am I doing the right thing? Here's what I'm getting: 2 exhaust cover gaskets; 1 driveshaft housing gasket; 1 upper housing gasket; 1 exhaust tube gasket;and 1 exhaust tube seal.
 
Re: Mariner 40B power head job

Sounds like you have all the gaskets you will need.

I do not use any kind of sealer (and none is recommended).

Anti-seize on the bolts never hurts (at least on any cover bolts).

And I agree that your base gasket (exhaust plate) is a likely candidate for water - particularly in the lowest cylinder..
 
Re: Mariner 40B power head job

Thanks alot for your reply Galamb. I'm a little anxious about the whole deal. Is there ahy thing else I should look at while I've got the power head off?
 
Re: Mariner 40B power head job

Since you are there, you may want to pick up a new seal (which may look like an o-ring or a tap washer - don't remember exactly on the "B" models) for the top of the water tube (where it connects at the base of the powerhead).

Most water tube parts are discontinued so this could be a "jury rig" job.

If it looks at all deformed or rotted or anything take it to a hardware store and see if you can find something close - one of those rubber washers for a tap would work if you can find one close in size.

That little (seal) is a less common point of failure on the cooling system - but since you will have access I would at least check it out...
 
Re: Mariner 40B power head job

Nice. I would have never found that, as it is on the gear housing diagram.There is a part shown on the top of the tube that's listed as a washer. I don't know if that is a rubber washer, or if I need to order the part shown at the bottom of the tube that's listed as a gasket.
 
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Re: Mariner 40B power head job

Yes, that (washer) is like a "tap washer" on a sink faucet.

Anytime you have things torn down it's best to try and replace any little seals etc that could cause you a headache at some later point.
 
Re: Mariner 40B power head job

I got it torn down tonight. I didn't take the exhaust cover off yet, but it looks like the exhaust plate was leaking every where. I'm still waiting on the gaskets. I was able to find that washer (and everything else) at sea-way.com. I took some pics. Well, what do you think so far?
 

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Re: Mariner 40B power head job

For a 30+ year old motor, it looks to be in excellent shape - of course it's always the "guts" that matter :)
 
Re: Mariner 40B power head job

Even though this is a "dry drive shaft" design outboard motor, I suspect the lower seal is allowing water in. After all those gasket changes without success, it's either the seal or a gasket SURFACE somewhere is warped.

Jeff
 
Re: Mariner 40B power head job

I got the exhaust cover off today. It's hard to tell from the pics, but both gaskets looked perfect. I don't think it was leaking there, but, at least, it won't be a posibility any more. Everythings cleaned-up and ready to go. Everything came apart easily eccept the lower cowel bolts which snapped. They had to be driven out. The nuts were NLA, of course, but I found some at the hardwear store. Now all I need is those gaskets. Welcome Jeff. If your talking about the lower "o" ring from the exhaust plate to the lower oil seal housing, I found that when I removed the power head. I didn't know it was there, so I didn't order one. I don't even know if I can find one as it is NLA. I didn't like the way it looked. It seemed loose. I was just going to put some grease on it. Any other sudgestions?
 

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Re: Mariner 40B power head job

Is there any hope for this motor? Everything seemed to go well on the assembly. It ran great in the driveway. I noticed alittle water seeping out at the top of the exhaust cover. I tightened it alittle more, and it stopped. I took it out for a test ride today. It ran great at first, but got alittle rougher on the way back (just at idle speed). I leaned it out some and it smoothed out. When I got home, I pulled the plugs, and they both had water on them. I retorqued the exhaust cover as much as I was compfortable (it only calls for 5ft.-lbs.). I also was able to get alittle more out of the exhaust plate-to-powerhead bolts. Is there any chance that this will do it, or do I have bigger problems? I can't imagine what; I've done just about everything to this motor. Help:confused:
 
Re: Mariner 40B power head job

Well, I'm still at it. I don't mind talking to myself, but I seem to get the worst advise that way. Ha! Anyway, I was able to solve the water on the intake manifold mystery; it seems that they sweat. As for the cylinders, I'm right back were I started. I was able to get the top one to stop leaking by retorquing. Today, I retorqued the power head to exhaust plate bolts and sheared one. It calls for 15-16 lbs-ft and I took it up to 20.They moved so easy! I'm going to pull it off and replace all the bolts. While I have it off, I'm going to do the head and cover gaskets. As far as I know, there is'nt much else left, is there? Should I buy new bolts for the head as well?
 
Re: Mariner 40B power head job

Just make sure the surfaces are clean before you put on those new gaskets.I talk to myself a lot,need to have an intelligent conversation now and again:D
 
Re: Mariner 40B power head job

I'm just glad that no one was there to here me talk to myself when that bolt sheared.:eek: Have you heard of anyone replacing the bolts with studs? I've heard it's supposed to be stronger because you're no tightening the bolt into the block.
 
Re: Mariner 40B power head job

On older engines like this, I ALWAYS run a large, fine file over all the gasket surfaces to clean them up. They never seal properly otherwise.
And I use a little Hylomar sparingly on any dry, paper type gasket.

Regards, Andrew.
 
Re: Mariner 40B power head job

On older engines like this, I ALWAYS run a large, fine file over all the gasket surfaces to clean them up. They never seal properly otherwise.
And I use a little Hylomar sparingly on any dry, paper type gasket.

Regards, Andrew.
Thanks Andrew, great advice. I just used a razor blade and some solvent to get the old material off. A local marina sudgested Johnson/Evinrude sealer for the exhaust plate (power head) gasket. I'm definently looking to do more this time. Thanks again, Rick.
 
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Re: Mariner 40B power head job

Hi, I'm back. My project has taken a new direction and I have some questions. I found a power head from a 1986 motor. It has good compression (125/130) and it looks real nice. I need to mount my intake manifold to the new power head but I can't find an outer intake gasket anywhere. The way I see it, I've got two options; either use the old gasket with out seperating the inner manifold from the outer manifold, or buy another inner gasket and trim it to fit. I have successfully removed the manifolds with out seperating them and would like to know which would be the best way to proceed. Could some one please give me their advice?
 

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Re: Mariner 40B power head job

That's exactly the kind of question I ponder often (whether or not to separate components that I don't necessarily have to), but I always tend to relent figuring if I don't replace the gasket/seal now while I have everything torn down and it's "right there", for sure I'll be ripping it down again real soon to replace what I should have when the opportunity was there.

Having said that I would never resuse an existing gasket - never.

If an original is not available I simply get a sheet of gasket material from any discount auto place and make my own using the old one as a pattern.

Alternately, as you note, if you can find one that is close enough to customize, that would work fine as well.

In any case, I really would replace it since you are there...
 
Re: Mariner 40B power head job

I'm with Graham: make a gasket Look for 1/32 " rubberized gasket material and have at it! Easy to do.

Jeff
 
Re: Mariner 40B power head job

Thanks for the advice guys. I'm heading out for some gasket mat'l. I'm also going to look for that Hylomar that Typhoon sudgested, as my service manual does call for sealer on the base plate gaskets. Now that I've pulled my old power head back off, I'm not to impressed with the Johnson/Evinerude gasket sealer I used. It hasn't set-up much more than it was out of the can. I'll take any other tips you guys have got on reassembly. Remember, I'm new to all this.
 
Re: Mariner 40B power head job

That OMC sealer is not supposed to set up fast--it's supposed to take its time. I use it for case sealing and fuel connections and it works great.

Jeff

PS: Please don't tell anyone 'cause I'm a Merc guy!
 
Re: Mariner 40B power head job

That OMC sealer is not supposed to set up fast--it's supposed to take its time. I use it for case sealing and fuel connections and it works great.

Jeff

PS: Please don't tell anyone 'cause I'm a Merc guy!
I'm not telling; I traded my Johnson for a Merc. Well I didn't find that Halomer, but I know it's a Permatex product, so I grabbed the gray. Is that gonna' work?
 
Re: Mariner 40B power head job

Most of the OMC sealers are long gone now - this is what I use:

Anything that called for "Adhesive M" (usually any rubber components - o-rings/grommets that needed to be glued in place) : any weather strip adhesive from the discount auto place.

Gasket sealing compound: Aviation gasket seal (the jar with the little brush connected to the cap) - I use Permatex brand, but any is fine.

Gasket dressing, Gasket maker or anywhere (except the crankcase halves) that calls for a sealer between metal parts "without" a gasket: Permatex 17BR (black)

Gel Seal for crankcase halves: Permatex 38401 "Motoseal" (grey) "gasket maker"

I have heard the strong opinions about using Permatex in place of the gasket maker but have personally never had an issue with it (bonding) - the biggest detraction I have found is that it's difficult to remove compared to other products - but for me, the permatex products are available locally and relatively cheap and they do work...
 
Re: Mariner 40B power head job

Permatex aviation gasket (the brown stuff in a little jar with it's own brush) is just a fantastic sealant for tightly machined surfaces. The aviation stuff was developed to bond aluminium and magnesium crankcase halves on aircraft engines, it's a very similar application to outboard engines.
You should be able to get the gaskets you are after (I think you want the gasket that fits between crankcase and reed block?), I've seen Sierra offer that sort of gasket for some engines and for sure if you buy a Quicksliver powerhead rebuild kit it will contain them.

Regards, Andrew.
 
Re: Mariner 40B power head job

That's the same stuff I buy in a can labeled "OMC Sealer". Good stuff. Gonna have to put a "Mercury" label over it, though. Might get caught!

Jef
 
Re: Mariner 40B power head job

I feel better now that every one has now agreed on one sealant. I did end-up with that gasket in my package I got today; Just a mix-up.
I've got a few more things to round-up and I'll be ready.
I was checking out some threads and came across one advising some one to reprime his parts before reassembly. Would that apply to my exhaust (base) plate?
Rick
 
Re: Mariner 40B power head job

On older engines like this, I ALWAYS run a large, fine file over all the gasket surfaces to clean them up. They never seal properly otherwise.
And I use a little Hylomar sparingly on any dry, paper type gasket.

Regards, Andrew.

Andrew,

I used the file on the base plate. I had to take off more material than I expected to get the surfaces even. When I was done, it left little scatches (probibly from the edge of the file). I used a fine wire wheel to get them out, which revealed some pitting. I'm assuming that these are the extreme situation that you use Hylomar, so I found some. The gaskets on both sides are the paper type. Do you use it as instructed, allowing it to set-up before torquing, or do you use it just like a sealant?
 
Re: Mariner 40B power head job

Andrew,

I used the file on the base plate. I had to take off more material than I expected to get the surfaces even. When I was done, it left little scatches (probibly from the edge of the file). I used a fine wire wheel to get them out, which revealed some pitting. I'm assuming that these are the extreme situation that you use Hylomar, so I found some. The gaskets on both sides are the paper type. Do you use it as instructed, allowing it to set-up before torquing, or do you use it just like a sealant?


Use it as instructed. I have also used, with good success, the high temp copper type silicone sealants on base plate gaskets. It takes the heat of the exhaust nicely. The adaptor plates under the powerhead on most all outboards is corroded when they're older, it always needs a little help with a good sealant and there's nothing wrong with using it.

Regards, Andrew.
 
Re: Mariner 40B power head job

Use it as instructed. I have also used, with good success, the high temp copper type silicone sealants on base plate gaskets. It takes the heat of the exhaust nicely. The adaptor plates under the powerhead on most all outboards is corroded when they're older, it always needs a little help with a good sealant and there's nothing wrong with using it.

Regards, Andrew.

It's all together now. Everything went well, and that Holamer was great to work with. It was very easy to control; just smear it on where you want it with your finger. No worries about clogging holes. It skins-over so fast that you can second coat it if you want it thicker.
I'm very hopeful that I got it this time. The exhaust plate to power head gasket, that I got this time, has a raised red ridge were it counts; around the exhaust and the water inlet on the plate side. You might think I'm going over-board, but I'm waiting until next week-end to run it.

Thanks to Everyone, Rick:)
 
Re: Mariner 40B power head job

I don't think you're going overboard at all! I will run a new engine till it's warm to the touch and shut it down for a few hours, to let the gaskets and sealers extrude and set up properly.
Call it paranoia, but I never get leaks!

Regards, Andrew.
 
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