Water on #4 spark plug

[BMsuper]

I have an 88 Mercruiser 4 cyl. 2.5 (chevy I am told) with an Alpha 1 outdrive in my 88 22' Starcraft Islander. My first boat.

I have had problems with a miss in cylinder #4. I changed the plugs and initally the engine ran great, no miss, however after a few days the miss is back and it caused the engine to stall at slow idle. It also seems to run hot but not according to the temp. gauge.

Today the engine ran great on the way out but after shutting the engine down for an hour or so it was hard starting and the miss was back. To get it started I have to give it a little throttle and run it at about 1,000 rpm for 15 seconds or so until #4 cylinder stops missing, then it runs fine at higher throttle levels.

I pulled the plug in cylinder 4 and swapped it with the plug in cylinder 1 and the miss went away for a short while.

While pulling into the dock at low speed/idle the miss started again and the boat stalled while trying to dock in the wind causing a small panic, but we got her tied down.

I again pulled the plug for #4 cylinder and I believe there was a drop of water on the electrode of the spark plug. If there is water entering that cylinder where could it be coming from? The oil is clean with no indication of water. I also changed the gas/water filter and drained and cleaned the gas tank.

Where do I start looking?

 

[Bt Doctur]

Re: Water on #4 spark plug

you have a hole in your exaust riser, if you wait you could stick the valve in #4 causing a bit more damage not to mention hydrolocking and cranking thru #4 cylinder

 

[achris]

Re: Water on #4 spark plug

Remove the exhaust manifold and riser and have then pressure tested... You'll probably need to replace them...

As the doc said, keep using the boat in that condition and you'll do a lot more damage.......

Chris..........

 

[BMsuper]

Re: Water on #4 spark plug

that sounds simple enough. Will any good marina be able to pressure test the riser and maniford?

Guess I better start pricing parts.

Thanks for the quick reply. I want to get it fixed before the season ends.

I'll post the results.

Bob F.

 

[achris]

Re: Water on #4 spark plug

My preference would be a Merc dealer for the pressure test. They are probably more familiar with what's required. Also check your engine oil, it may have water in it... If it does, then when you get the new bits, you'll need to do an oil and filter change a few times to clear the water out...

Chris........

 

[BMsuper]

Re: Water on #4 spark plug

Sure enough the exhaust/intake manifold did have a hole and crack about 1/4inch wide in the exhaust portion of the manifold. I'm surprised the thing ran.

I ordered the manifold and riser, well see if that fixes her up.

I'll post the results.

Thanks, Bob

 

[BMsuper]

Re: Water on #4 spark plug

I ordered the manifold and riser from ebasic power online out of North Carolina. When the parts arrived because of poor packing most of the gaskets were crushed and bent.

Before I ordered the parts I talked to the tech guy at ebasic power as my manifold was not listed and was superseeded by a new "will fit" manifold and I wanted to make sure it was going to match up. The manifold did bolt on however there were many differences that caused a lot of extra work.

First the manifold did not come with new mounting bolts. My existing manifold bolts only threaded in about a quarter inch. I suppose it's enought to hold but they should have included new bolts the correct length to properly mount the manifold.

Then there is a threaded drain port at the bottom of the manifold. The supplied plug did not fit the threads so I had to drill and tap the hole to 3/8" pipe thread and buy a new plug.

The old manifold has the hose bib in the front plate, the new manifold has a hose bib that threads into the top front of the manifold so the hose didn't fit. I had to use the old front plate with the hose bib and plug the hole on the top of the manifold.

Then to top it off the mercarb trottle linkage hit the top of the manifold when mounted requiring a 3/8" spacer to allow the linkage to go back to idle. I couldn't find a spacer so I ended up cutting off the bottom part of the linkage (the part that advances the throttle slightly when full choke is on) so the throttle would go fully back to idle.

Now I've got her back together and fired it up with the water collar on to see if everything is going to work. It runs fine with no leaks so I removed the plug in the top of the manifold where the hose from the thermostat would have gone to If I didn't use my original front plate with the hose bib.

With the engine running water is pumping out of this hole with the plug removed which I think is a normal indication that the water is circulating properly. However when I shut the engine off the water drains down about
2" below the top of the manifold.

Where is this water going? Shouldn't the manifold stay full to the top with the engine shut down, as it has to go up the elbow and out of the riser to exit?

Tomorrow I will drop her in the water to see how she runs.

 

[achris]

Re: Water on #4 spark plug

You are going to hate what I am about to say, but here goes....

The above story is exactly why I stick to OEM... When Merc superseded that manifold to a new number it included all the hardware you need to put it on an engine that had the original. That includes the right length bolts, the spacers plates and any new hoses required to successfully complete the job.

And this is the bit that really bites... I have seen enough rusty manifolds that are 'after-market' that have died after only 2 or 3 years in service... I have cut them open and guess what I find? The castings are a lot thinner than OEM... You get what you pay for....

Chris...........

 

[BMsuper]

Re: Water on #4 spark plug

I believe you are right. The manifold was casted so cheaply, even the gaskets didn't fit right. I guess this is part of my learning curve.

I still don't know why the manifold doesn't stay full of water when the engine is shut down? The only thing I can think of is the bottom of the riser where the water exits out the exhaust is lower than the top of the manifold so maybe the water is siphoning down to that level?

Either way she goes in the water tomorrow for a shakedown cruise. It's getting cold though, was in the 40's this morning here in NY.

 

[BMsuper]

Re: Water on #4 spark plug

I dropped her in the water yesterday. It ran good right from the start, idled good. I shut it down for an hour or so and it restarted good. Did this several times then took her out for a little 3/4 throttle. About 5 minutes into 3/4 throttle it just shut down.

It seemed to be overheating, (it did this before the new manifold and riser was installed). Gas was dripping into the venturi and the engine was hot. Maybe vapor lock?

I also checked for spark and I did not have spark at the plugs? I'm wondering if there is a high temp. cut off switch? After removing the distributor cap the second time and playing with the points the spark came back. I don't know if it was as a result of the engine cooling off (if there is a high temp cut off switch) or mabe the points had a burr on them. Either way the engine started and I got back to the dock.

Further inspection shows water in the oil. It looks like a weak milkshake. I never had water in there before?

So what is my next move. I did a compression test and got the following results.
#1-142, #2-128, #3-135, #4-130 Dry. #1-170, #2-160, #3-175, #4-155 Wet.

I guess I have to remove the head and inspect the head gasket and cylinders. I should probably remove the circulation pump and check the vanes on the pump. I have a new impellor kit that has yet to be installed.

This thing is starting to get me. It seems I am always working on the boat.

 

[achris]

Re: Water on #4 spark plug

I dropped her in the water yesterday. It ran good right from the start, idled good. I shut it down for an hour or so and it restarted good. Did this several times then took her out for a little 3/4 throttle. About 5 minutes into 3/4 throttle it just shut down.

Not good!

It seemed to be overheating, (it did this before the new manifold and riser was installed). Gas was dripping into the venturi and the engine was hot. Maybe vapor lock?

Also not good... Check the needle and seat in the carb. That's one that you really need to fix.. Was there fuel in the clear green tube between the fuel pump and carb?

I also checked for spark and I did not have spark at the plugs? I'm wondering if there is a high temp. cut off switch? After removing the distributor cap the second time and playing with the points the spark came back. I don't know if it was as a result of the engine cooling off (if there is a high temp cut off switch) or mabe the points had a burr on them. Either way the engine started and I got back to the dock.

No high temperature switch...

Further inspection shows water in the oil. It looks like a weak milkshake. I never had water in there before?

Probably from the leaky manifold... Water enters a cylinder through an open exhaust valve and runs down past the piston rings and into the oil... It only turns to 'milkshake' when you run the engine... The milkshake is emulsified oil and water...

So what is my next move. I did a compression test and got the following results.
#1-142, #2-128, #3-135, #4-130 Dry. #1-170, #2-160, #3-175, #4-155 Wet.

Those results aren't too bad, and, in my opinion, don't warrant pulling the head...

I guess I have to remove the head and inspect the head gasket and cylinders. I should probably remove the circulation pump and check the vanes on the pump. I have a new impellor kit that has yet to be installed.

I would pull the leg and check/replace the water pump impeller before doing anything else. And if there wasn't any water flowing, I'd now be checking the water pocket cover in the top section of the leg...

This thing is starting to get me. It seems I am always working on the boat.

Sorry, welcome to the world of boats.... Your engine is now 20 years old.. She's looking for some attention... The other option is expensive (I know, look at my signature)

Good luck with it all... and when you feel down... come here and we'll give you a hand.

Chris...........

 

[BMsuper]

Re: Water on #4 spark plug

OK, I pulled the bottom half of the outdrive and installed a new impellor although the old one looked brand new. There was water going through the manifold because I pulled the plug on top of the manifold before I put it in the water and water came out of that plug.

I also pulled the circulation pump and that looks good also?

I am in the process of changing the motor oil and I guess I'll drop her back in the water and try it again.

I don't think I was getting spark for a short time when the motor overheated so I am going to replace the points and condensor.

It is possible the coil could go bad intermittently?

If the compression is adequate does that rule out a head gasket leak? I'm running out of ideas.

A new engine is arount $2,400 for the 2.5L.

Thanks for your help, Bob.

 

[achris]

Re: Water on #4 spark plug

Bob,

Good luck with all that.. I have had a coil go bad..

New engine for $2400, but that is the engine only, not including the leg and transom plates...

The compressions didn't look like a bad head gasket... Bad head gaskets usually show up as two adjacent cylinders low... like 1-2, 2-3, 3-4... and you would see numbers like 50...

When you have the lower unit off, have a look up into the bottom of the top unit and look at the plastic cover... If it's melted or distorted, then that needs to be replaced too...

Chris.........

 

[BMsuper]

Re: Water on #4 spark plug

Well, I took a couple of weeks off from the boat. Went away with the motorhome.

Finally got back in the water today. It ran really well. No miss, even at very low idle. The oil is still clean after running it 3 hours. It did not overheat as in the past so maybe the new impellor in the lower housing did make a difference. I did not run long at wide open throttle, ( I usually don't) but did a steady cruise at 3,200 rpm at about 25 mph. That's good enough for me.

I really enjoy the boat when I don't have to worry about getting stuck, especially out in the shipping channel where it can be 190 feet deep here on the Hudson River in (NY). These big tankers do not stop for you.

Now if I could only catch some fish. That seems to elude me. I gotta learn how to fish.

Thanks for the help, Bob F.