1986 170hp 3.7l (224ci) Mercruiser - Antifreeze/Coolant

moosejaw

Cadet
Joined
Jul 12, 2004
Messages
12
Just started using my "new" boat with this motor in it. Runs great, has 350hrs on it and it purrs like a kitten and has lots of power. (47mph in a 18ft fglass deep V). Temperature gauge doesn't get much over 150F once warmed up. <br />Anyways, the only thing is, it seems to smell a little like antifreeze/coolant when it's running and when I look at the motor it is green where the exhaust reservoir tank bolts down to the exhaust manifold like the gasket is leaking a bit and dripping and getting hot and making the smell. I ran a tank of gas through it (say 40-50 miles of use)and when I checked the antifreeze/coolant level there is none in the reserve/plastic bottle but when I pop off the "rad cap" off the exhaust reservoir tank its full, so maybe I lost a pint or less in a day. The plastic bottle was to the full cold line when I checked it before I used it. There is no antifreeze/coolant in the oil or anything like that so it's not a head gasket issue. I was wondering if I just need to tighten the exhaust reservoir down (4 bolts) to seal it up where the gaskets meet or if this is a common repair (replace gasket). Also the reserve tank is tucked up under the engine compartment and I don't know how the heck you would ever fill it. Do you just add it at the engine and the plastic tank fills up when the antifreeze/coolant heats up or what?<br />Lastly, I know I have great oil pressure when I start the boat and it also is well over 60lbs at WOT once it gets warm, but when I drop it to idle after it warms up it drops down about 10-15lbs. Seems a little low but it could be a gauge inaccuracy thing or is it normal for them to have low oil pressure at idle? <br />I have a manual but it really lacks some detail and was hoping someone with experience could offer comment.
 

Bob_VT

Moderator & Unofficial iBoats Historian
Staff member
Joined
May 19, 2001
Messages
26,034
Re: 1986 170hp 3.7l (224ci) Mercruiser - Antifreeze/Coolant

I have the same motor and set up. The 4 bolts alonge with all the other ones have torque specs. Do not over tighten.<br /><br />I would get a better manual. I got one off ebay that was specific to the 470/3.7 liter.<br /><br />There is a gasket between the parts. You might have a hair line crack in your manifold that only expands when it gets hat. (I had one and ended up replacing the manifold). You can just buy the gaskets and remove the whole works to examine the parts. I would strongly suggest that you get a tap and clean out all the bolt holes before your re-assemble.<br /><br />I would pressure test the system.<br /><br />The oil pressure could be from many factors. Oils level, viscosity, sending unit, old age..... as I stated get a better manual.<br /><br />Good luck.<br /><br />Bob
 

MrBill

Senior Chief Petty Officer
Joined
Aug 4, 2002
Messages
710
Re: 1986 170hp 3.7l (224ci) Mercruiser - Antifreeze/Coolant

As Bob suggests, pressure test the system...it's definitely going somewhere. You should also be aware of the 3.7L coolant leak issue from the cam seals. On the 3.7L engine the closed coolant water pump on the front of the engine is driven by the cam shaft (not the best of engineering designs). When the seals wear, coolant will begin to leak from the hole underneath the front of the water pump...that's when you'll know its time to replace the seals. Sorry I'm not on my regular computer to provide the link which explains this 3.7L issue.
 

8AteEight

Petty Officer 3rd Class
Joined
May 23, 2005
Messages
79
Re: 1986 170hp 3.7l (224ci) Mercruiser - Antifreeze/Coolant

Ooh, do you have that link now?? I have a big "water in oil" issue now, and I think this might be why. Mine is an '85 merc 170.
 

devisetek

Cadet
Joined
May 10, 2005
Messages
27
Re: 1986 170hp 3.7l (224ci) Mercruiser - Antifreeze/Coolant

I know its a little off topic, but what size and pitch prop do you have on there? I also have the Mercruiser 3.7 (mine is a 165) on an 18' V Hull boat, and I am only seeing about 40 mph. Boat weights in at 1900 lbs according to manual.<br /><br /><br />Just curious how to coax out a little more speed.
 
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