[dsteding]

I have 2000 Yamaha 115 four stroke, was out Saturday and had loss of power/missing issues. The diagnosis this morning was a blown head gasket.

A couple questions:

1) We think (this is a new to me boat) this may have been caused by the exhaust port being submerged when launching and idling at the dock (we are divers, this is on a 18 foot Avon RIB, it was loaded heavy in the stern). Could this be the cause? I think the take-away here is loading the boat differently and launching it with the motor trimmed up a bit.

2) The mechanic is mentioning cylinder head replacement as well. Uggghhhh. How often is this needed when you blow a head gasket, and (go ahead, slap me when I'm down) what is the ballpark cost?

-Doug

[Silvertip]

A blown head gasket is not typically a reason to replace a cylinder head. If water injestion is the cause you could have bent some valves and even that would not be reason to replace the head. New valves would take care of that issue. Are you saying the engine is running when you launch? If so, there is no cooling when the engine is out of the water so an overheat condition may have caused the blown gasket. Overheating can also crack a cylinder head and in that case, yes, it is necessary to replace it. Head gaskets can blow for no apparent reason so replacement of the gasket is all that's necessary. It all boils down to what actually happened. Are you telling us the whole story? As for cost -- well lets just say you aren't going to like it and since Christmas is coming, consider it a very expensive Christmas Gift to yourself.

[dsteding]

Thanks for the reply-I promise I'll give all the info I can.

No, the engine isn't running out of the water. I launch with the motor off, get it in the water, and am usually able to push it off the trailer. It is a pretty light boat.

But, in water, at the dock, it had the exhaust port submerged, basically blowing bubbles when idling. I was wondering if the submerged exhaust ports equaled water getting into the exhaust manifold-maybe the backpressure there blew the head gasket. But, pure speculation on my part.

I don't think it overheated, there weren't any alarms, and it seemed to be running fine, just rough. No real production of white smoke or anything like that either. That being said, this is a new motor for me, so I'm still getting familiar with it.

There was water in the oil, and also a bit of oil/water mixture around the air intake.

-Doug

[EDIT] Just got a message from the tech, he's saying a complete powerhead replacement, but I don't know the basis for this.

[dsteding]

Okay, one tech is saying new powerhead and new cylinder heads.

The thing is still running, however.

I got a second opinion, and am taking it to that shop-they think it could be a few things, none of which involve replacing the powerhead.

[rodbolt]

when you at the techs shop look for a minimum of 4 stroke certified,advanced 4 stroke would be better and a master tech certificate from yamaha wont hurt.
yes I have seen the odd head gasket fail just cause.
rare but it happens.
before I replaced the block I would assemble it,after having the head checked at a competent machine shop,leave the cams out and perform a leakdown test.
would be nice to do a leakdown test prior to engine dissasemply to check cylinder sealing condition.
if after head gasket replacement the leakdown test looks good finnish the assmbly and run it.
job isnt hard for the average backyard guy as long as the service manual is followed closely.
clean all the valve shims and carefully mark them with a magic marker for correct reassembly or you will find its a time consuming process to reshimm all the valve lash clearences.
always use new headbolts on final reassembly as they are an angle torque fastener.

[dsteding]

Thanks rodbolt and Silvertip.

Turns out what was happening was water intruding through the upper exhaust port-the boat was a bit loaded down in the back (and, even though this boat is rated for a four stroke 115, RIBs in general haven't adapted to the extra weight of a four stroke). We had loaded it on the trailer, and then I dropped it in with the motor down, I'm guessing that procedure led to the motor getting fairly far down in the water while it was off.

I took it to a different shop and the tech flushed the motor, he said he did 4-5 oil changes on it over the course of yesterday. No blown gaskets, no structural damage, the oil was actually still fairly viscous. The plugs were a bit fouled and the oil filter was obviously shot, so he replaced those and adjusted the ECM. It is running like a champ now.

I'll be shifting weight forward in the boat, and will be mindful of not submerging that exhaust port, the boat will go in with the motor up, and I'll keep it slightly trimmed up while idling around.

At the end of the day, it was a full day's work and a tune up on the motor. $700 in total costs, which is the easiest $700 I've ever spent.

I've also found a great shop, Jacobsen's Marine here in Seattle (actually out in Ballard). They were great to deal with.

-Doug

[rodbolt]

which goes back to what I said, a leakdown test will not only show the cylinders ability to sael but if it cant seal then it shows what is leaking.
there is no ECM adjustments on that motor, the TPS voltage is about the only adjustment possible.
glad your problem was a simple one but always have a cylinder leak down test run when testing a 4 stroke.

[dsteding]

Yeah, my bad-not ECM, just a tune up. I was relaying what I got over the phone.

Compression was fine, the mechanic was able to see what had happened in terms of water intrusion from the exhaust, so I don't think he did a leakdown.

I'll get it out soon for a test run.

[rodbolt]

a compression test on a 4 stroke outboard is a teat on a boar hog.
have a leak down test done.
its faster and vastly more accurate than a compression test.

[dsteding]

An unfortunate update:

Leak down it will be.

Took it out last week, ran it for ~2 hours at 4100-5000 rpm. It ran like a champ.

Today, I checked the oil, it came gushing up out of the dipstick.

White/grey in color, slight gasoline smell to it.

We all assumed it was water from the upper exhaust port being submerged, but now I'm not so sure. Maybe thermostat sticking?

This isn't fun, that's for sure.

[rodbolt]

when you do the leakdown test make sure you you carefully listen for air in the crankcase.
if that motor cannot turn 5700 RPM with its normal load it will make oil.
also carefully check the VST vent for a VST float needle leak and the fuel pump diphram for leaks.
the fuel pump can be tested with a standard pressure vacum tester without dissasembling the pump.
the odds of injesting water via the bottom cylinder while running due to engine weight is someplace between slim and none.
quit hunting that field.

[dsteding]

Leakdown test results:

Cylinders 1, 2, and 4 are all less than 5%

Cylinder 3 is at 30%.

The tech hears some hissing through the oil dipstick hole. He's going to get on the phone with Yamaha and talk with them a bit.

[rodbolt]

and yamaha is going to tell them,like I am, to do a thorough decarb job preferably with the YDIC injector set up.
then retsest.
if the numbers come up you may be ok,if not its possible to have gasses leaking past the headgasket,along with cooling water, into the crankcase.

[dsteding]

There was a massive amount of water, relatively speaking, in the oil.

1.5 hours of operation equaled overflowing oil from the dip tube.

Yamaha thought it was corrosion in the oil pan for some reason, or an outside chance of a blown head gasket.

We're pulling the heads off now.

[rodbolt]

sometimes being the Easter Bunny just aint no fun.
it will help if you and your tech will sit down and figgure out a hunt plan.
first,was water entering a cylinder? spark plugs will show distinctive marks and colors for water burn,especially salt water.
the reason I say the submerged idle relief cannot allow that kind of water when running is simple.
you will bend a rod due to hydrolock first.
now, where can we leak water in and not oil out?
any corroded spot in the cooling system that enters a non pressurized spot in the crankcase/oil sump area including any failed gaskets.
any spot on the head surface with oil drain backs near a cooling water passage.
30% leakage isnt good but I dont think your going to see a piston ring or valve problem.
thats why I would decarb BEFORE pulling the head and recheck #3.
easter egg hunting can cover a lot of territory,the object is to narrow the hunting grounds.
I personnally dont like easter egging a problem but occasionally its simply part of the job.
the trick is to carefully analyze all the information about the hunting ground,eliminate the areas you can first then go hunting with an educated plan.
wont be the first time I have had to make plates and such to use air pressure to pressurize blocks,heads,adapters and such.
occasionally you simply have to understand how it works and create a plan to elimintae sub assemblies one by one.

[dsteding]

Yes, this isn't fun.

The plugs were clean-so no water was getting into the cylinder. Given that the air from the leak down test was exiting into the oil pan, our theory is that we're getting water migrating from the cooling channels between the block and the head to the oil channels in the same area-and the most likely cause of that would be a leak in the head gasket.

But, I think I'm seeing your reason for decarbing first (which might be too late). If the 30% was fixed by the decarb, then that suggests the corrosion in the oil sump area.

[EDIT]

It is not the head gasket. The thought now is water intrusion in the oil pan area, funny thing is it doesn't happen when in the tank at the shop (i.e., they ran it and no water got in the oil) but it does happen when loaded down and running out on the water. Makes me think something is a bit more submerged when I take it out as compared to the shop conditions.

Originally Posted by rodbolt

sometimes being the Easter Bunny just aint no fun.
it will help if you and your tech will sit down and figgure out a hunt plan.
first,was water entering a cylinder? spark plugs will show distinctive marks and colors for water burn,especially salt water.
the reason I say the submerged idle relief cannot allow that kind of water when running is simple.
you will bend a rod due to hydrolock first.
now, where can we leak water in and not oil out?
any corroded spot in the cooling system that enters a non pressurized spot in the crankcase/oil sump area including any failed gaskets.
any spot on the head surface with oil drain backs near a cooling water passage.
30% leakage isnt good but I dont think your going to see a piston ring or valve problem.
thats why I would decarb BEFORE pulling the head and recheck #3.
easter egg hunting can cover a lot of territory,the object is to narrow the hunting grounds.
I personnally dont like easter egging a problem but occasionally its simply part of the job.
the trick is to carefully analyze all the information about the hunting ground,eliminate the areas you can first then go hunting with an educated plan.
wont be the first time I have had to make plates and such to use air pressure to pressurize blocks,heads,adapters and such.
occasionally you simply have to understand how it works and create a plan to elimintae sub assemblies one by one.

[dsteding]

Another update:

Got on the phone with Yamaha, talked with Chris. Super helpful, we walked through the parts diagrams.

It isn't the head gasket, so things are focussing on the oil pan area. The powerhead is coming off soon, I'm going to go visit (and take pictures) today.

I'm thinking this was something that was a long time coming, I bought this motor in October, and have only 10-12 hours on it. I'm hopeful the seller (a friend of a friend) will work with me if it turns out this would have happened regardless of who owned it-i.e., if I hadn't bought it in October, he'd be the one with this headache.

Edited to add some pictures:

[dsteding]

We've got the powerhead out. The upper exhaust port was fairly corroded, the tech said about half of it was gone. The oil pan was not out as of about 5 pm yesterday, so we still haven't zeroed in on the water issue.

That will happen after Christmas, I think we're getting closer, and one of the things that will come out of this is that all the gaskets will be new-as well as any parts that need replacing below the powerhead. I guess that is a silver lining.

[AGENT 37]

I fought with a F100 that was doing the same thing but the corrosion I focused on was the cylinder head. I had it welded and machined. I completely rebuilt the power head and had it apart several times, and went through a lot of gaskets because the leak just would not stop. The oil pan gasket surface did not look compromised at all to me but on a whim I bolted my rebuilt power head on to the lower section of a completely different motor (F75) that I found in the bone yard and it all stopped. I had no more water in the oil and the engine performed flawlessly. Apparently the oil sump was corroded through. From what I found out, it isn't the most common problem but it does happen. It can be difficult to pinpoint exactly where those leaks are at and get them all fixed. Water in the oil can have a snowball effect that leads to other problems such as rod bearing failure and cylinder wall damage. Engine oil just does not have the same anti-wear capability when it is watered down, especially when it is salt water. I hope that the problem gets fixed before it gets worse. Rectifying a leak is certainly less painful than completely rebuilding the motor. When it all gets put back together check the color of the oil very often when you start running it. Once it starts to turn milky you know that your oil is not good. I would not run the motor to the point that the lube system is overflowing. Hopefully you will have no trouble with it though. Good luck!

[dsteding]

Originally Posted by AGENT 37

The oil pan gasket surface did not look compromised at all to me but on a whim I bolted my rebuilt power head on to the lower section of a completely different motor (F75) that I found in the bone yard and it all stopped.

Interesting. We've yet to really eyeball the oil pan gasket, but I wonder if it is worth replacing the oil pan when it is torn down?

It is only a $300 part, and with what I've spent just to get to it, it may make sense.

How's the powerhead running now? Any long-term issues once you bolted it on to the F75?

[dsteding]

An update, we're thinking it is the surface on the exhaust guide above the oil pan, if you look at the bottom of the sealing surface of this picture, you'll see some black corrosion and it is rough to the touch:



The same surface is on the right side of this picture:



The gasket from that location has some corrosion on it too, see the bottom of this pic:



But, the oil pan itself looks fine, see it in the background here:



We're at close to $3000 in terms of repairs, we're debating whether the exhaust guide needs to be replaced. Part of me thinks it could reseal if cleaned and using sealant, part of me wants to put a new one in because I don't want to spend the labor costs involved to get at it again.

[rodbolt]

dunno, nothing really jumps out at me.
use NO sealents on any rubber parts unless specifically recommended by the service manual.
if you must use a sealent on the metal gaskets,even though its not really reccomended, then a product like BRP/OMC gel seal II or its locktite equivalent will work ok.
use a scotch lock pad or its equivalent to clean the gasket surfaces then use a straight edge and a .003" feeler guage to check surface flatness.
myself I would have removed the powerhead with the cyl head still installed and made a plate to pressure test the cooling system and would do it before reinstalling the powerhead.

[dsteding]

Originally Posted by rodbolt

use a scotch lock pad or its equivalent to clean the gasket surfaces then use a straight edge and a .003" feeler guage to check surface flatness.
myself I would have removed the powerhead with the cyl head still installed and made a plate to pressure test the cooling system and would do it before reinstalling the powerhead.

If it is flat, is there any reason to put a new exhaust guide in?

Agreed re plate and pressure testing, that would have been a bit more of a efficient way to do it, in retrospect.

[rodbolt]

a reason to replace the exhaust guide I dont see, however pictures are not as good as real life which isnt anywhere near as good as simply using a dye penatrant to check for cracks or pinholes.
the kit is about 25 dollars and is a two part spray. one is a dye/penatrant the other is a developer.
works great to find cracks and pinholes.
use the old base gasket as a template, dont worry about the holes fwd of the crankshaft, drill the mounting holes in a piece of 3/8ths or 1/2 AL plate.
drill 1 hole in the center of the exhaust outlet about 1/4.dril 1 1/4 hole in 1 oil retrurn passage
drill and tap 1 hole in the plate water inlet to the block. I would tap it 1/4 NPT.
use a leakdown tester or equivalent and apply air at about 30 PSI.
leakage above 0% indicates a leak.

if it leaks use soapy dishwashing liquid and find out where its coming from.
what the attempt is to isolate what part of the syatem is leaking.
have the combustion chambers,valveseat areas been dye cheked for cracks?
your on an expensive easter egg hunt.
try to stack the odds of finding the golden egg in your favor.

[AGENT 37]

$3000 is a very pricey easter egg hunt.....

I didn't get near that much into my project. I was actually looking into getting a different motor before I fixed mine. I ended up with a good motor and put under $1000 into it. I ran my rebuilt power head on the F80 (it was actually the cowling that was from a F75) parts for 54 hours without any problems. I sold the motor last summer along with the boat.

My oil pan looked perfect but still leaked. I'd also leak test the oil pan separate from the power head. If you have corrosion in one spot it is usually all over the inside. The pan can get corroded from the outside in as well as getting corroded from the inside out through the cooling and exhaust passages. I was amazed when I figured it out. I believe that may have been the problem to begin with and not the cyl-head that I had welded and milled. It is certainly not cheap or fun to troubleshoot water in the lube system.