1985 75 hp mariner wont start

[temple1975]

I purchased a new to me mariner seems to be fresh water only engine. Anyway I took it for a quick spin after I mounted to the boat, it idled fine and ran fine for a little run of about 75 yard then it sputtered and stopped. I tried a few times to crank the engine but could only get the engine to run with throttle the throttle advanced. I cleaned the carbs but still could only get the engine to run with the throttle advance. I just did a compression check and have 150 dead on across all four cylinders. I then inspected the plugs and found a small ring of rust on the #2 cylinder.

My assumption is that my water jacket seal is leaking water back into the cylinder ? IF my fuel was contaminated I would expect to see a small amount of rust on all the plugs ?

I certainly do not want to risk breaking exhaust bolts if I don't have to. But is there any other way to get water on just that plug ? I compression tested the engine before I bought it and did not notice the small rust ring before. By rust ring I mean like rust had been lightly brushed on by a brush not eating into the plug or anything.

thanks in advance for any advice

 

[Texasmark]

The water jacket cover has 4 holes in it for your plugs. There is no separate head, just the jacket so there isn't any way to get water in the cylinders from around the plug if it's installed and torqued. I think it's 25 inch ounces on plug torque. How much is that, a good snug and a little tap on the wrench.....remember you are seating into aluminum casting material and it's soft so don't over do it.

If your engine has been sitting up for awhile expect fuel problems. How did the inside of the carbs look? Any foreign material like would come from a degraded fuel line? Varnish? Did you attempt to use the squeeze bulb as a water pump to ensure that your fuel pump was not the problem when you stalled out? Checked fuel lines for cracks? Fresh 50:1 fuel oil mix?

 

[temple1975]

Sorry I meant the exhaust water jacket where the tell tale hooks in. (as possible source of the small amount of rust only on the one plug at the base) The inside of the carbs did not look varnishy , the primer bulb was good and hard, I didn't try to keep pumping the bulb in the water but did try to keep pumping when on the muffs at home, didn't see any cracks or fuel leaks indicating line crack, I did notice a black residue on the fuel connectors going into carbs I assume from ethanol break down. When I took off the fuel line and rubbed my finger on the connector it was kind if sticky and looked like an ink smudge on the fingers

The plugs were finger tight plus around 1/8 turn.

 

[Texasmark]

Go after the fuel lines. I had a similar problem on an engine that was only 10 years old. Even though I had an inline filter between the fuel pump and the carbs, I still found pieces of hose in the carbs. On my carbs the high speed jet is mounted in the bottom of the bowl and I accidentally found my main problem which dislodged with a blast of compressed air after I did the cleaning process. It was intermittently blocking the HSJ on one of my 3 carbs. The rest of the hose problems were in the low speed circuit of another carb, more little pieces of black rubber.

 

[temple1975]

I found this in my manual ....


So here's my game plan, rebuild the carbs , rebuild the fuel pump, replace the fuel lines, hopefully get it running then reinspect the plugs. My previous engine leaked from the exhaust cover gasket which resulted in water in all cylinders very obvious , this is a little more subtle. I think I have a combination of small issues leading to big.

I did not find any obvious particles from fuel lines in the carbs but that doesn't mean i blew something out of them and didn't see it !

Thanks for the advice TexasMark

 

[temple1975]

18 up 18 down on the exhaust bolts. I used a old butterfly impact and sloooooowly worked them out. White knuckled two at the bottom with straight ratchet but got them out. One of the last bolts was saturated with oil / fuel , some where quite rusty so I think this was a wise move especially since no bolts broke. I will have my local marina inspect my baffle plate and replace if needed. Hopefully will get it back together Saturday and fire it up. I then need to work on getting a dumb temp buzzer since there currently is not one.

 

[Texasmark]

When you reinstall your bolts use blue locktite (I think permatex has the same thing with a different name) which is a thread locker but also helps to prevent corrosion. Blue is made for removal. Red is referred to in the manual but having used it in industry, it is for bolts that are NOT to be removed. Requires heat to melt it and lots of work. No need for it, blue does just fine....auto parts stores has it

 

[temple1975]

cool thanks for the tip