Seized Mariner Magnum II 150

[Floater49]

I just bought a 1988 Baja 196 Sunsport in like new condition. The problem is the motor. 1988 motor with oil injection removed. It's been run on 50:1. Apparently it ran good this year once and then on the second run, it slowed down and stopped. It had been in storage for 3 years. I can get it to turn over by turning the flywheel but it is really tight. No grinding or any strange noises when turned over. plugs look good and the pistons have no evidence of damage to them. It seems like a seal has balled up or something. Does anyone have any ideas?

 

[orbanp]

Re: Seized Mariner Magnum II 150

A bad seal will not slow down an engine! It sounds more like an overheated engine or an engine run without or with not enough oil.
When you say that the "pistons have no evidence of damage to them" how did you determine that?
You could use some boroscope to inspect the inside of the cylinders to see if they are scored.
I am not familiar with that particular engine, but you might be able to remove the exhaust covers and see how the pistons and rings look like at exhaust ports. If the pistons seized in the cylinders, it will show there!
I would squirt some lubricant into the cylinders and see if that frees them up. Measure compression after that.
Any chance that the lower end is dragging your engine?
If lubricating the cylinders does not help, remove the gearcase to check if that is causing the trouble.
In the worst case you might need to open up the engine.

Good luck, Peter

 

[Capt Ken]

Re: Seized Mariner Magnum II 150

The key to the problem is the statement that it had been in storage for three years. You didn't clean the carbs or fuel system nor did you replace the water pump. You ran the engine with gummed up carbs and leaned a cylinder. That caused severe overheating in the cylinder and gaulded the piston. Time for a rebuild or replacement.

 

[Floater49]

Re: Seized Mariner Magnum II 150

Thanks for the input. I pulled the plugs and looked inside for signs of damage to the tops of the pistons like you would see if the rings broke up. For the record, this is how I bought it on saturday. I got the info from the previous owner. I suspected a rebuild was in order but hoped for a better prognosis. I really expect that Capt Ken is right. I suspected the same thing when the guy told me about it.
Any idea what a rebuild or replacement is worth?

 

[Bamaman1]

Re: Seized Mariner Magnum II 150

It's just hard to say what a rebuild would cost in parts. If you're mechanically capable, you might want to buy a repair manual and begin disassembling the engine.

Remember that there are very few moving parts in a 2 stroke motor--just crankshaft, connecting rods and pistons. All parts are available online for very fair prices.

Worse come to worse, part the engine out on EBayMotors.com and find yourself another Mariner or Mercury 150 hp of the same vintage.

 

[Floater49]

Re: Seized Mariner Magnum II 150

Update:
Pulled the heads off and it turns out the top cylinder starboard side had a leak in the head gasket. Fortunately, it must have just happened and there was no damage yet. Good thing I looked.
So I then pulled the L/U off. Amazingly, the powerhead spins freely on the starter or by hand. Impeller was dry and 3 vanes broken off. I can not turn the input shaft by hand. My suspicion is there is bearing issues downstairs. I will tear it down and rebuild the LU. I will replace the whole water pump assembly and replace the head gaskets. Then do the carbs and it should be as good as new. There wasnt even a ring ridge on any of the cylinders and the cross hatch looked relatively new. Pistons are standard bore.
I wonder what the cost will be for the LU rbld...

 

[orbanp]

Re: Seized Mariner Magnum II 150

Update:
...
Impeller was dry and 3 vanes broken off. I can not turn the input shaft by hand. My suspicion is there is bearing issues downstairs. I will tear it down and rebuild the LU.
...
I wonder what the cost will be for the LU rbld...

It is good to hear that at least the powerhead will be ok!

When you say 3 vanes were broken off, are those missing pieces accounted for? Hopefully they are not in the powerhead clogging water passages. In other words, find the pieces if they are missing!

As for the lower unit, depending what you find, it could be cheaper to find a used LU, or a whole motor with a blown powerhead.

Good luck, Peter

 

[Faztbullet]

Re: Seized Mariner Magnum II 150

I wonder what the cost will be for the LU rbld...

Cheaper to buy a SEI unit new as they come with 3 year warranty.....

 

[1FASTLASER]

Re: Seized Mariner Magnum II 150

Cheaper to buy a SEI unit new as they come with 3 year warranty.....

+1..........way cheaper and already proved themselves as far as a GOOD product that they stand behind

 

[wired247]

Re: Seized Mariner Magnum II 150

+1..........way cheaper and already proved themselves as far as a GOOD product that they stand behind

I'm on my 3rd SEI lower on 3 different motors and am wearing an SEI T shirt right now. Great products. I remember the bad old old days of $2400 factory lowers. Never again. The SEI stuff is top notch and the warranty is great but Ive never had to use it.

 

[Floater49]

Re: Seized Mariner Magnum II 150

Starting to wonder if I shouldnt do that. I looked into it yesterday and found that the upper cone tapered bearing on the driveshaft piled up. The race was in pieces and the rollers were all flat. I'm sure filings went downstairs so a complete rebuild will likely be in order. not too worried about reinstalling everything but it's the clearances that I am unsure about. Assuming the gears are good, I think I will replace the bearings and gaskets and see how it goes. I will have to buy some specialized tools, but hopefully it will be worth it in the end.