Trying to bring a 1992 Mariner 150 out of hibernation

BTL

Petty Officer 2nd Class
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Feb 22, 2017
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Recently purchased a 1989 Wellcraft 18 Sport with a 1992 Mariner to work on as a project. When I bought it, the boat had been sitting unused for about 5 years and the motor wouldn't start. The starter would rise but couldn't turn the flywheel. I've made some progress and now have no trouble getting the flywheel to spin, and it tries to start...but dies immediately.

Here are the stats and what I've done so far:

1992 Mariner 150 V6 Serial # OD177534
Cylinder compression: 90, 110, 110, 110, 110, 110
New lower unit had just been installed before I bought the boat.
New battery
Replaced starter
Cleaned out cylinders and replaced head gaskets
Replaced blown voltage regulator (was blown before purchase)
Pumped out old gas and replaced with fresh
Replaced fuel hose
Replaced fuel/water separator
Primer bulb stays hard

I haven't replaced the plugs yet but I've checked them with a spark tester.

Here's a video of what happens when I turn the key. I removed the air box because I wanted to see if the carbs were getting fuel, and it appears that they are, but I don't know if it's enough.

https://youtu.be/p4Q4lhE5FVo

I can't tell if this is a fuel, mechanical, or electrical problem. Anyone have an idea of what's going on, or what I should try next?
 

Chris1956

Supreme Mariner
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Mar 25, 2004
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She puffs smoke, so she is firing. The carbs are likely clogged, or the choke (enrichener) may not be working.
 

BTL

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She puffs smoke, so she is firing. The carbs are likely clogged, or the choke (enrichener) may not be working.

The choke seems to be working, so I guess the carbs are probably clogged up. I was hoping I would be able to start it to run some cleaner through, but it doesn't look like that is going to happen so I guess should probably just bite the bullet and rebuild them all.
 

racerone

Supreme Mariner
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Why was compression low on 1 cylinder.?-----Clean carburetors are VERY important on a 2 stroke motor , so clean them.----Does spark jump a gap of 3/8" or more, yes or no ?
 

BTL

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Why was compression low on 1 cylinder.?-----Clean carburetors are VERY important on a 2 stroke motor , so clean them.----Does spark jump a gap of 3/8" or more, yes or no ?

I don't know why the compression was low, there's nothing visibly wrong with that cylinder. Hope it's not a piston ring or something. Not sure about how far the spark jumps, I used an inline spark tester to check them. I will check them again tonight.
 

Glastron_V210

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Jan 28, 2009
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To me that sounds like your ignition is cutting off....perhaps your ignition switch is screwed up...

You could check the M contacts to make sure they are not making contact at any other position except off.

Or you could pull one wire off the M contacts....just remember that there is pretty high voltage there and you will have to hook it up again to stop the engine!


Chay
 

BTL

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Well I went to check the plugs again tonight and now all 3 plugs on the port side aren't firing at all. Other side is fine. So I'm guessing that's most likely due to a bad switchbox.
 

BTL

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I cleaned the carbs and installed new gaskets. New switchboxes should be here soon. I'll update after I install them.
 

BTL

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So the carbs are back on, I installed the new switchboxes, and now I think things might be worse haha. I'm now getting no spark, and when I crank the motor I get an alarm that doesn't stop until I turn the key to off. Both oil reservoirs are totally full so I'm not sure what that's about.

I did a resistance check on the stator and trigger and both were good so the loss of spark really confuses me too.

*edit:

Ok, the lack of spark was just my spark tester messing up. I got the engine started for the first time! But...I'm still getting that alarm. It's a constant BEEPBEEPBEEPBEEP that doesn't stop until I turn everything off. Guessing it's related to the oil injection system.
 
Last edited:

BTL

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I figured out the problem with the oil injection system: the pump drive is not working.

I hooked up a tank of premix, disconnected the oil pump output line and started up the motor. No oil coming out. Then I disassembled the pump and found no apparent problems so I moved on. Next I tried running with the oil pump removed completely and I found the problem: the drive is not turning.

So my question is, is there any way to remove the oil pump drive coupling from the powerhead to fix or replace it? I figure it's either seized or broken. Worse case scenario I'll just run premix forever, but I'd like to fix it if I can.
 

Chris1956

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Mar 25, 2004
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There should be lots of postings on how to convert a Merc to premix. I think you simply pull out the pump drive shaft, although I have never done it myself. Merc sells a block off plate to replace the pump, but my motor simply has the oil lines connected to themselves and the pump body reinstalled after the driveshaft was removed.
 

Chris1956

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Oil pump drive gear is on crankshaft. I have heard they strip easily. Most convert to premix when that happens.
 

BTL

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Thanks. Sounds like losing the pump and using premix is the way to go.
 

racerone

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Oil pump drive gear on the crankshaft is " plastic "---Sounds like another one is history.
 

QBhoy

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Don?t use the oil injection on this engine. I learned the hard way with a same age Merc 200. Disconnect the oil injection. And premix 50/1. Known for failure by numerous means and your mind will never be at rest.
Wouldn?t worry too much about the low compression on one cylinder just now. I had the same issue bringing a 90hp Merc out of long term storage. One of the three cylinders was down by 30 psi on the others. I left 2 stroke oil down the bores for 24hrs...gave her a run rich mixture with oil and the low cylinder cane back up.
 

BTL

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Thanks guys! Premix it is. I'm gonna order the block off kit today.

Got a bunch of work to do on the trailer then it will be time for a test drive to find out what else needs fixing lol.
 
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