Mariner 150 overheated browned cylinders melted plug wires.

[imthemedic]

I was WOT down the lake and it lost power the died. Steam was pouring out of it. THe motor wouldnt turn over it was locked up. No buzzer and I didnt notice the pressure gauge. I hadnt realized what had happened at the time. I waited a while and tried to start it and it clicked the first time then broke free and cranked over then started. It was making a popping noise and wouldnt take throttle ran a just over idle speed. I shut it off then removed the cover to find the problem. It got so hot it melted the insulation on the cover. The cylinders and head had turned brown. The plug wires had melted on the right side. A ruff first day out! Do you think the whole motor is shot or is it reasonably fixable? Any ideas? Anyone have stuff lying around to fix it? Im on a tight budget.

 

[WillyBWright]

Re: Mariner 150 overheated browned cylinders melted plug wires.

Any motor that overheats to the point of siezure is almost certainly seriously damaged to the point of needing an overhaul. You won't know the full extent of the damage til you get it apart. Check compression, or at least look at what's on your sparkplugs. If you see metal on any of them, you'll know for sure it needs an overhaul. Is it a V-6 or an inline-6?

 

[imthemedic]

Re: Mariner 150 overheated browned cylinders melted plug wires.

1985 Mariner 150 V6

 

[redjmp]

Re: Mariner 150 overheated browned cylinders melted plug wires.

Well first off you never run at WOT for more than a minute or so.
Would you redline your car all the way down the highway?
Do as Willy says and check compression and inspect plugs for metal deposits.
You might have got off easy and the compression will still be reasonable.
Then you would just need to change out the impellor. Perhaps your overheat was due to a bad head gasket or a warped head?
Otherwise you need to do a teardown and inspect the cylinders for scuffing.
At a minimum you would need to hone out the bad cylinders and replace the rings.
If any pistons are melted or damaged they would need to be replaced but only the bad ones. If a cylinder or 2 are badly grooved or scuffed, then only those holes need to be rebored and oversize pistons installed.

 

[WillyBWright]

Re: Mariner 150 overheated browned cylinders melted plug wires.

I have to disagree with redjmp's statement about full throttle operation. Marine motors (including both sterndrives and outboards) are specifically made to be able to operate at full recommended RPMs, which isn't quite the same thing as redline. Redline is higher and they don't tell us what that is. That's why propping the motor for achieveing full recommended RPMs is important. Too small and you can blow a powerhead by overrevving. However you will definately save gas by backing-off to about 7/8 throttle and only lose a few mph.

Since it's a V-6, you might as well pop the heads off and have a look. You can't do that with an inline. Red's right on target about warped heads and blown gaskets. You might even consider simply turning the flywheel with the sparkplugs out. If you need more force to turn it in any area of rotation, that's a problem.

 

[jdupree]

Re: Mariner 150 overheated browned cylinders melted plug wires.

I have to disagree with redjmp's statement about full throttle operation. Marine motors (including both sterndrives and outboards) are specifically made to be able to operate at full recommended RPMs, which isn't quite the same thing as redline. Redline is higher and they don't tell us what that is. That's why propping the motor for achieveing full recommended RPMs is important. Too small and you can blow a powerhead by overrevving. However you will definately save gas by backing-off to about 7/8 throttle and only lose a few mph.

Since it's a V-6, you might as well pop the heads off and have a look. You can't do that with an inline. Red's right on target about warped heads and blown gaskets. You might even consider simply turning the flywheel with the sparkplugs out. If you need more force to turn it in any area of rotation, that's a problem.

I have a 200 V-6 Mercury 1992 model. What would be the max rpm's I should run this motor. Thanks

 

[gss036]

Re: Mariner 150 overheated browned cylinders melted plug wires.

I cruise my 89 Merc 200hp around 42-4300 @ 30+ - mph. Max RPM @ 5400-5500. I figure I am getting about 2 miles per gal doing this speed/rpm.

 

[emckelvy]

Re: Mariner 150 overheated browned cylinders melted plug wires.

A few things to consider: You didn't say how old the impeller was or if you had any idea why the motor lost cooling. For example, if on a very fast boat it might have been trimmed out too far, losing water pressure.

Too bad you didn't get a good read on the pressure gage before she fried, it would've told you a lot.

Since the motor got so hot it siezed, that bodes badly for the pistons/rings. At minimum pull the heads as suggested. May as well also pull the exhaust manifold outer cover and inner plate, as the gaskets are fried and it'll leak water like a sieve if they're not replaced.

With the exhaust covers off, you can view each piston thru the exhaust port. Since the exhaust side is going to show the most damage, you'll know right away if the motor needs to come down. Piston scoring, piston ring or piston ring land damage will be very apparent.

If it doesn't look hurt, you might get away with renewing head gaskets (check heads for warpage), new exhaust gaskets, new thermostats & poppets (they are surely fried too), new water pump kit.

HTH, G'luck and let us know what it looks like.....ed

 

[imthemedic]

Re: Mariner 150 overheated browned cylinders melted plug wires.

I pulled the heads and exhuast off today. The 2 top pistons are fried, the edges are gone and pieces of the rings are bedded in the face of it. Of course the domes are beat all to pieces. The middle 2 pistons look like they seized the rings. The bottom 2 looked fine. I figure 4 pistons,6 rings, 2 sleeves, 2 bores, and 2 hones. Sucks
I friend of mine has a 200 merc with a busted bottom end. The top is in good condition. Could I just bolt the top on mine with no problems?