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1985 Mariner 200hp project.

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rixter66

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I just purchased a 200hp Mariner that runs, but the previous owner thought one of the cylinders might be scored. The alarm went off after the rev's got high, and then he shut it off. Just curious if this is an engine worth spending time and money on, or should I just part it out? I have not had a chance to do a compression test or even fire it up yet. Will post when I do.
 
Hi rixter66,What made him think the pistons were scored? Can you do the work yourself? How much are you prepared to spend? I don't know how much a rebuild kit would be but at a guess $700 - $800,plus a boring if the cyls are scored and outsize pistons.I have seen guys here saying $2000.The up side is that you have a practically a new motor and a whole new pool of know how.But first the compression numbers,then spark, and after that cost the parts that you'll need,then you can figure if you want to go ahead.
 
Ok, here goes. After a few minutes of watching it sputter, the engine fired up. Of course I forgot to open the cowl up and look at all the plugs before this.:eek: The motor was sputtering and cutting out, so I checked out the rest of the motor and noticed all the plug wires were off the cylinders on the right side as you face the rear of the motor. Put them on and the sputtering stopped. It didn't quite run right, so I checked the plugs again and they were all only finger tight.
I was happy the thing ran and then went to test compression. Al the cylinders were between 130-135psi. So far so good.
Now my first question is how are the cylinders numbered? I did notice a discoloration in the paint around the left top cylinder casing as you face the motor from the rear. Is this normal? The color looks like a bronze sheen to the grey paint.
Second, all I have is the water hose attachment for the cooling system. Is this going to be enough circulation for this motor in order for me to check if the overheat sensor kicks on?
 
Re: 1984 Mariner 200hp project.

More information. Spoke with the person I bought the boat from and was told the alarm only went off when boat was in water and engine was under load at full throttle. I started it up this morning on the hose and ran it for about 20 minutes. Seemed to have a bit of a miss-fire at first, but cleaned up after a bit. I checked the block temp with an infra-red thermom and the bottom was at about 125F and increased to 145F at the top. Both sides were consistent in the temp range. The motor was run in both reverse and forward for a bit, and only for a few seconds at WOT.
Does this sound like a normal running motor?
 
Never run a motor at WOT on a hose,--------------Just not good for a motor !!--------Install a new impeller and check head bolt torque.
 
isnt the alarm for the oil pressure? That would isolate a lot of what you are looking for. Compression is good. You need to get a manual, that will help. You can run sea foam through the engine, that will help clean the insides, I would change the plugs anyway, and at least check the impeller like Raceone said, since thats one of those things you want to do anyway, but look over your oil sending unit, (assuming you have one anyway).
 
Thank you all for the info. I am going to get an impeller kit this week and try to get the boat on the water this weekend. I also noticed on of the plugs was a Champion while the rest were NGK. Would this make a difference in the running of the motor? I plan to get all new NGK plugs also.
 
They have an oil level alarm in the tank.-----------------some ( not all ) have an alarm for when the oil injection pump stops rotating and stops putting oil into the gas.This is due to the plastic gear on the crank having disintegrated.
 
This motor does not have oil injection, it's the old fashioned pre-mix. When I get the impeller instaled and new plugs, I'll take it for a run on the lake and let you know what happens.
 
I'd mix it a little heavy on oil if it's been sitting a while for the first tank. The Merc V6's are all pretty sweet engines and reasonably hard to kill.
 
I was wondering what I need to do as far as storing the motor after I finish the few things on it. Does anything special need to be done. I plan to remove it from the boat and place it on a dolly in the shop.
 
Drain ALL the fuel from the carbs and fuel lines.

Fog the cylinders and make sure it is stored upright so there is no hater trapped inside the cooling system.

Weekly you should go out to the garage, pet your motor, say nice things to it!! :D
 
All marinas sell the " fogging " compound in spray cans.-----------Spray into carburetors on a running engine .------this coats all internal components.-------Then drain carburetors.
 
Do not use WD40 since it will wash the cylinder walls. If you have a can of sea foam deep creep it will be better. Yes, many places sell fogging oil which also works fine. I am partial to sea foam since it has multiple uses. Do not forget if you have any pre-mix fuel left to use stabil or liquid sea foam in it.
 
You can " play " with this ------------start motor and disconnect fuel and time how long it runs.-------Then fill carburetors and start motor again.-------Inject lots of fodgging oil so that you are done when carburetors run empty.---------On the other hand you can drain carburetors easily on that motor.-Just remove plug / jet on the bottom of the bowls.
 
I am not a fan of running them dry. It does not insure that ALL the fuel is out and the lubrication on your bearings goes away. I have seen fuel left in one or more of the carbs when the engine stalls out. I personally prefer the drain method.
 
How does the oil " go away " when you run carburetors dry??????????------I think this topic has been discussed before with great confusion.
 
Last edited:
racerone said:
How does the oil " go away " when you run carburetors dry??????????------I think this topic has been discussed before with great confusion.
Click to expand...

Lubrication only occurs while running with fuel oil running through the cylinders.

If any carb should run out first then you are intentionally moving a piston in a dry cylinder and the amount of oil to hit the bearing is dissipated and they are being moved without constant lubrication.
 
How does the oil " instantly disappear " between a piston skirt and cylinder when a carburetor runs out and only dry air is pumped through those 2 cylinders ?????
 
Got the gear box off and replaced the impeller. I noticed there was one side of the upper gasket that looked like it had been blown out. Could this have been the cause of the overheat? The replacement kit seemed to improve the water discharge out of the prop. I did notice there was a black soot type film over the drive shaft. Is this normal, or is there an exhaust leak I need to be worried about? Other than that it fired up after a few coughs, so now it's time for a trial at the lake.
 
Finally had some time to get the boat into the water. Ran it 3/4-Full throttle for about 20 minutes and no alarms. It seemed to hesitate a bit but I think that's just the carbs needing adjustment-tuning. I did notice there wasn't a strong stream of water coming out the pee hole, mostly intermitent. Is this normal, or should it be a steady strong stream? Overall I am happy with the purchase, $500 for boat-motor-trailer. I really appreciate all the input from everyone and will get back on line when the motor eventually makes it on the 26' RIB I will be building this spring. Thanks again.
 
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