Mercury XR6 Engine Trouble

[Saiyajin]

Hello Everyone!

I recently purchased a boat with a 150hp XR6 Mercury engine. The engine ran fine until just a few days ago. I noticed when I first bought the boat, that the tach didn't work. I read online that this was due to the voltage regulator failing or being on its way out. I decided to swap the tach send from one regulator to the other and the tach worked fine... but it only worked for a few minutes and then quit!

The next day, I took the boat out to the lake and after I got on plane I went wide open trottle and got it up to 50-55 mph. The boat suddenly started losing power and I quickly put it in neutral fearing the worst. After a few seconds the engine died on its own. I tried to turn the boat over and I only heard a clicking noise.

After waiting for a few minutes... I tried to start the boat and it ran great at idle so I tried to get back on plane and stay at around 30 mph, but the boat did the same thing! It lost power and died! After this happened, the boat wouldn't start and I had to use the trolling motor to get back to land (2-3 miles away).

I checked the voltage gauge and the batteries were around 10-20% and when I checked them before heading out it had said 50-60%


While I was still at the lake I took the engine cover off and I noticed that the bendix on the starter was stuck up! I hit the starter a few times and got the starter to kick back down.

Once I got to the boat ramp I swapped out the battery with the trucks and tried to see if it was the batteries that were the problem. This did not help and the starter kicked up and started to turn the flywheel a little bit, but the boat would not turn over completely.

I wiggled the flywheel back and forth and got the Bendix to kick back down and I then tried to manually turn the flywheel. The engine however, wouldn't turn completely over. It would turn fine and then "hit" something and I would turn it around the other way and it would "hit" something again.


So my main questions are this.

1. Could the problem be electrical? If so, what should I check first? Is there a sensor that prevents the engine from turning over completely, even by hand?

2. Is it possible that the engine isn't turning over because the boat is still "stuck" in gear? By this I mean the boat may have "died" while in gear (I don't remember). If I put it in neutral with the boat "off" would the transmission still be engaged?


2. If the safety switch is in the "off" position, will the engine turn over as long as you turn the key?


3. When I first got the boat, you couldn't leave the engine in the "crank" position indefinitely. If the engine didn't start after a few seconds you would have to wait to try again. If I tried to turn the key to the "crank" position instantly after it didn't start, it wouldn't even click. Is this some sort of safety feature that might be preventing the engine from turning over completely?

4. Could my engine be done? I thought an engine wouldn't move even slightly in either direction if it was "seized" or had thrown a rod.



I appreciate any help I can get! Thank You!

 

[Chris1956]

It sounds like you have multiple issues. The most important is to see if you bent a connecting rod or have a bad gearcase. Remove the spark plugs and turn the flywheel by hand. If she will not turn over 360* plus, remove the gearcase and retest. If it is the gearcase, new ones and used ones are available. If it is the powerhead, that is a worse issue.

Post back.

BTW - The VRs are likely shot, and the bendix needs to be cleaned and lubed with oil. The wiring is suspect and the starter may (may) have issues. These are secondary, IMHO.

 

[Dukedog]

What Chris said except tha starter thing. Tha things tend ta stay ingauged till it starts or a certain rpm is reached whether it starts or not. If you just barely "wiggle" tha flywheel tha bendix should drop, if not then ya got a problem with it................Right now tha starter thing is minor! Hope its a gear case problem for ya...

 

[Saiyajin]

I ended up taking off one of the cylinder heads and the worst case scenario was indeed confirmed.


The engine appears to have completely melted the very top starboard side piston.

While I was under the cowling I went ahead and did a compression test and the rest of the engine appears to test at 120.

I have attached some pictures!

1. Does anybody know what may have caused this failure? How can I diagnose the possible cause?

2. It appears that there are crosshatch markings on the other cylinders. Does this mean that this engine has been rebuilt previously?

3. Will I be able to hone or bore the "bad" cylinder, or will I need to replace the entire sleeve?

4. Will I be fine with just replacing the "bad" cylinder and rod without having to touch the rest of the engine? (The rest of the engine cylinders all tested at 120 PSI)

Thanks in advance for any advice or feedback you can provide!

 

[Chris1956]

The crosshatching on the good cylinders may be from the factory. There is no good way to tell, unless the pistons are obviously aftermarket. The damage to the one piston/cylinder was likely a result of a clogged carb barrel, as that motor should have 3 two barrel carbs. The bad cylinder would need to be bored, and a new oversize piston and ring set installed. The carbs need to be cleaned and the timing checked before operating, or it will just break again. I am presuming that motor has cast iron cylinder liners.

 

[Faztbullet]

Answer to your questions:
(1) idle stablizer/advance box (2) Nope ..you will need to mike each cylinder for wear (3) you can bore up to .040 oversize doubt it will be honeable (4) You wont know till its torn down as a lot of trash will swap in the cylinder thru exhaust, usuall #3 and #6 will show some signs.

 

[snowbrd84]

From what I have heard, these motors are pretty famous for building up carbon on the rings, the ring finally catches on the exhaust port and breaks. This happened to me last year with my 150 XR2. Ring broke, went into the lower bearing, destroyed it, destroyed piston, but did not destroy the cylinder. I was able to tear it down, hone the cylinder, new piston, new lower bearing, rebuild with all new gaskets, and have perfect compression in that cylinder.

Is that aluminum from the piston on the cylinder wall? Or did the cylinder wall itself get damaged? You can resleeve for a couple hundred bucks if the cylinder wall is that badly damaged. If you plan on rebuilding yourself and then taking the block to a machine shop, it is doable and will cost you maybe around $500. Your looking at $100-150 for a complete gasket kit for the motor. Piston and rings for that cylinder should be less than $75ish. You may want to re-ring all, I didn't and had no issues. I did remove all rings and thoroughly clean out all carbon buildup though. Probably 200-400 at the machine shop depending on what it needs. If its more than that, its probably not worth "fixing". You can find a good condition block for around that same cost... All told, your looking at around 500-600 if you can do the rebuild yourself.

At the end of the day, I wish I had just bought a different motor and saved myself alot of headaches, but if it has sentimental value, thats a different story obviously.

 

[CVX20SPRINT]

From what I have heard, these motors are pretty famous for building up carbon on the rings, the ring finally catches on the exhaust port and breaks. This happened to me last year with my 150 XR2. Ring broke, went into the lower bearing, destroyed it, destroyed piston, but did not destroy the cylinder. I was able to tear it down, hone the cylinder, new piston, new lower bearing, rebuild with all new gaskets, and have perfect compression in that cylinder.

Is that aluminum from the piston on the cylinder wall? Or did the cylinder wall itself get damaged? You can resleeve for a couple hundred bucks if the cylinder wall is that badly damaged. If you plan on rebuilding yourself and then taking the block to a machine shop, it is doable and will cost you maybe around $500. Your looking at $100-150 for a complete gasket kit for the motor. Piston and rings for that cylinder should be less than $75ish. You may want to re-ring all, I didn't and had no issues. I did remove all rings and thoroughly clean out all carbon buildup though. Probably 200-400 at the machine shop depending on what it needs. If its more than that, its probably not worth "fixing". You can find a good condition block for around that same cost... All told, your looking at around 500-600 if you can do the rebuild yourself.

At the end of the day, I wish I had just bought a different motor and saved myself alot of headaches, but if it has sentimental value, thats a different story obviously.

Reusing old rings is something that I would never do personally.If they're coming out for whatever reason there's new ones going in.Can't see a used ring ever seating properly in a newly honed cylinder.JMHO

 

[snowbrd84]

I only honed the cylinder that was getting a new piston, and that cylinder did get brand new rings. The other 5 had perfect compression, and I was on a budget. So I cleaned and reused the rings and pistons for those cylinders. Definitely would NOT recommend reusing, but I did reuse on the 5 good cylinders and it worked great.

 

[Saiyajin]

Thanks for the feedback guys! I really appreciate it!

There isn't any "sentimental value" in the engine YET!!!

I'm trying to get it fixed as cheap as possible right now, since I haven't even had this boat for more than few months ! (bummer)

I think I'm just going to end up ordering a 0.030 over piston+ring and leave the other cylinders "as is". I won't know if I need to order a new rod and bearings until I REALLY tear into the engine. The metal on the sleeve is from the melted piston! It doesn't appear like the iron cylinder sleeve got cracked or damaged, so I should be able to save some cash by not having to resleeve (hopefully).

When I bought the boat I noticed that the paperwork said that the fuel line and primer bulb had recently been replaced. This leads me to believe that the old one was shot and the old line probably ended up clogging a jet or fuel line going to the carburetor!

I have the Mercury manual so I need to read up on how to "rebuild" and "inspect" the fuel system to save me a little bit of cash!

I don't really have the 80$ an hour going rate right now to have a shop do the work for me.
Then again, I'd hate to do a shotty job and have the engine go out on me....




Does anybody know a good website to order the gasket kit from? Thanks!