1979 Mercury 700 70 hp, Water squirts out vent?

[mckeemm]

Hi guys,

I have a 1977 merc 700, 70 hp, 3 cyl. There is a vent hole on the side of the cylinder block adjacent to the throttle arm etc. When I run the engine above idle I get an occasional squirt of water out the vent hole. There is evidence that this has been happening for a while. (stain on the block) I just purchased this engine and it has been stored for the last 3 years, outside under a roof but open to the Canadian summer and winter temperatures.

My question is what is this vent for and do I have a problem?

Any help much appreciated.

Thanks, Mark

 

[tashasdaddy]

Re: 1979 Mercury 700 70 hp, Water squirts out vent?

are you sure thats not where the hose to the telltale connects to the block? if it is you should get constant water flow. suspect impeller.

 

[mckeemm]

Re: 1979 Mercury 700 70 hp, Water squirts out vent?

are you sure thats not where the hose to the telltale connects to the block? if it is you should get constant water flow. suspect impeller.

Definatley not the "telltale". I just replaced the impeller and that part of things is fine, good flow at the telltale. The vent hole I'm talking about is on the linkage side of the motor. It's an .050" hole in a round boss on the engine side cover.

 

[fishingdan]

Re: 1979 Mercury 700 70 hp, Water squirts out vent?

Sorry, but that doesn't sound normal. Can you take a digital picture and post it?

On the powerhead, the tell tale port should be the only water exit.

 

[Plainsman]

Re: 1979 Mercury 700 70 hp, Water squirts out vent?

You can upload your picture to www.photobucket.com and link it here.

 

[emckelvy]

Re: 1979 Mercury 700 70 hp, Water squirts out vent?

It's been quite a while since I've worked on one of these 3-cyl "monstrosities", but if I recall there's a poppet valve in there along with a spring and diaphragm and maybe even a thermostat. I expect that the diaphragm is leaking when the poppet valve lifts.

Noting that this happens when you rev the throttle and water pressure jumps up, it makes at least some sense!

At any rate, you'd have to pull the entire exhaust cover assy to inspect/renew the parts. If this motor has seen salt use, the bolts are probably going to be stuck. Use heat and penetrant to help get them loose. DO NOT use more than normal hand tool force on the bolts or they'll break, and drilling stainless bolts out of aluminum is a miserable task indeed!

Worst case, drill the bolt heads off then pry the exhaust covers off over the 'studs'. Once the covers are off you can soak/heat/vise grip the reluctant bolts.

After it's apart, inspect the inner exhaust baffle for corrosion/perforations and replace as necessary.

Carefully clean all the gasket surfaces and reassemble. If you use the new-style impregneted gaskets there's no need for gasket dressing of any kind. If not, I like to use Permatex #3 or an anaerobic-type of sealer like OMC Gel Sealer or Loctite (Permatex) brand.

Very Important is to torque the cover bolts to the proper values or it'll leak. 200 in-lbs on the 5/16" bolts and 115 in-lbs on 1/4" bolts according to my Seloc manual.

Of course the Very Simple Solution would be to RTV, JB-Weld, or Marine Tex the offending leaking hole but I suppose that would be cheating!!

HTH...........ed

 

[mckeemm]

Re: 1979 Mercury 700 70 hp, Water squirts out vent?

Thanks for the info. What you say makes sense. The exhaust cover will definitely need to come off to repair the offending part. I believe that some sort of pressure regulator lives under that cover however I have read elsewhere that these motors run without a regulator or thermostat. I have not found a diagram of this system in my seloc manual. This is a Canadian manufactured motor and carries a Canadian serial number. Fresh water only.

I figured that as long as I had good cooling flow no harm would be done to try it out so I put it in the water on Sunday. The engine loads up with fuel at idle but runs fine at WOT, 32 mph flat out with two adults on board.

The primer does not get hard and fuel leaks out the air bleeds when pumping the primer. I suspect the needle valve are not seating. Carb kits are on order. I also have a charging system failure so I have ordered a new rectifier. Due to the amount of corrosion on the leads I can’t even remove them without destroying the old rectifier.

We’ll see how it goes.

My manual does not contain an exploded diagram of the exhaust cover side of the motor. I have not found one online either. If anyone can direct me to a diagram or list of part numbers for what lives in there I would greatly appreciate it.

Thanks, Mark

 

[mckeemm]

Re: 1979 Mercury 700 70 hp, Water squirts out vent?

Does anyone have an OEM manual with diagrams or Part numbers for the gaskets and poppet/diaphragm assembly?

1977 Merc 700, 70hp, 3 cyl s/n (4571652-4825249)

 

[ronnieboy]

Re: 1979 Mercury 700 70 hp, Water squirts out vent?

go to mercury parts express, input your serial numbler and you get all the diagrams and numbers .

 

[mckeemm]

Re: 1979 Mercury 700 70 hp, Water squirts out vent?

go to mercury parts express, input your serial numbler and you get all the diagrams and numbers .

Ronnieboy,

Been there done that. The program does not recognize my serial number so I cannot get past page one.

Any Ideas why?

My Canadian serial number is (7101012), Which according to the cross-reference chart on http://www.maxrules.com/merc_contents.html equates to model year 1977 US s/n (4571652-4825249).

The parts express does not recognize any of these numbers.

OEM parts list is p/n 90-75508. I'm looking for a copy of that as we speak.

Mark

 

[emckelvy]

Re: 1979 Mercury 700 70 hp, Water squirts out vent?

I'm thinking you may have better luck finding diagrams at the Doug Russell site. The Merc Parts Express site is good but only goes back so far. Obviously they don't want you to fix your old motor but buy a new one!!

Try this:


http://www.dougrussell.com/partscat...,2,12,10,15,11,4,9,16,17,18,19,0,21,20,13,6,5

You'll have to copy the entire link into your browser window, as this site has chopped off part of the link and it won't work by just clicking on it.

If that page is not it, back up to the main site and try again:

http://www.dougrussell.com/partscatalog/collections/index.cfm?fuseaction=collectdetails&colid=01

HTH...........ed