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Really bad compression #'s on one of my 225's.

Agree that the port engine looks fine on a cold compression test.

IMO the starboard is crazy. It tells me that the valves are not seating properly. There can be several causes - cam wear, cam bushings, or cam out of alignment. Or valves burnt, scored, or bent. The other possibility is a cracked head, but that is extremely rare on a Honda. Any way you look at it, you are going to need to pull the heads and have them micro-flux'ed and refurbished. Also have the cam mic'ed out to be sure it is in spec. That will also give you the opportunity to inspect the cylinder sleeves and piston heads in detail.
 
Yes, that likely is the next step. My question is, however.....can it be determined (via scope or some other tool) that the coolant passages through the heads aren't corroded? For the same reason that it's risky to rebuild a saltwater block, it would be a disaster to rebuild the heads if they are 20 hours away from the first pinhole.

Can the health of the heads be determined, regarding corrosion? I've never gotten that deep into a motor.
 
Btravlin2 - I cannot definitively answer your question, but I would contact the shop where you plan to have the heads refurbished and ask them if they can do an internal inspection of the water passages in the head - let them know your concerns. Way back in the cobwebs of my memory, I seem to remember a few years ago a company came out with some product that would chemically bond with aluminum to re-enforce it and harden weak spots. You might want to try an Internet search on something like that. It may have been in Popular Mechanics.
 
I'm now understanding the dilemma that is presented by a saltwater motor. A normal response regarding my motor, if it were freshwater, would be to rebuild it......an easy enough job, and not that pricey doing it myself. But I've been told the coolant passages in a block can't be accessed sufficiently enough to verify the level of corrosion, which would reflect in the thickness of the walls separating water from the internal areas of the motor.

So I could rebuild the motor, and two weeks later develop a pinhole leak, wasting the rebuild. The same thing could happen with the heads, unless the passages in them can be inspected beforehand.

Even further, I can see where in a worst case scenario the situation with this motor could lead down a path of no salvation. Specifically, if I recondition the heads, it makes sense to re-ring the pistons. And to do that, I have to get into the crankshaft. So while I'm in there, I might as well replace all the bearings. Now it's a rebuild. But the cyclinders could be hours away from a pinhole. So all this time and money gets spent on a gamble, all because a saltwater block can't be trusted.

Am I wrong about any of this?
 
Aristikat was running in the saltiest of saltwater in Florida with early 225's. He put over 3000 hours on those engines and just recently repowered. You very well may be fretting about a non-problem. I just don't know. I've been running exclusively in saltwater with my 225 on the Chesapeake and off Hatteras since the spring of 2008, have over 1900 hours on the engine and no sign of significant corrosion that I am aware of. Of course, I keep the boat on a lift (except at Hatteras) and flush after every use.

If I were in your position, and the trade-off was rebuild the heads or re-power, I think I would take the chance and do the re-build. Just my two cents worth.
 
I've decided to get to the heart of the matter. Tomorrow I will pull the heads. I'll look for signs of overheating and water intrusion. If the cylinders aren't pitted or scored, I'll have the heads reconditioned.

It's an odd mystery because of the imbalance of the comp numbers. My understanding is water intrusion is usually limited to #3 and #6 cyls, being physically the lowest. However, compression on #3 is the highest at 205, while comp on #6 is the lowest at 105. If water degraded #6, why nothing on #3?

The 2nd lowest is #1 at 132. The 2nd highest is #4 at 182. Don't these numbers seem strange? How could water get to #1, but not #4?

So I'm somewhat hopeful that the issue isn't due to water intrusion. That leaves valves that are not seating correctly in 4 of 6 cylinders. What could cause that other than the valves getting hot? And then again, if the valves got hot, then it stands to reason that the entire motor got hot. Wouldn't that damage the pistons and rings?
 
Just to make sure we are talking about the same cylinders - the starboard side from top to bottom is 1, 2, and 3, the port side top to bottom is 4, 5, and 6.

But anyway you look at it, it seems really strange. The port side would make some sense if there was water intrusion, but the starboard side is totally screwy. Anyway, you are approaching the problem just as I would. Please keep us posted.
 
chawk_man said:
Just to make sure we are talking about the same cylinders - the starboard side from top to bottom is 1, 2, and 3, the port side top to bottom is 4, 5, and 6.

But anyway you look at it, it seems really strange. The port side would make some sense if there was water intrusion, but the starboard side is totally screwy. Anyway, you are approaching the problem just as I would. Please keep us posted.
Click to expand...

Yep, the cyl #'s are correct. I have some other things to do, so it will be a few days.
 
Take a look at this. Here is the layout of the results. There appears to be a pattern.

Port .......Stb
182 ........132
160........ 170
105 ........205

#1/6 are low.
#3/4 are high.
#2/5 are moderate.

It seems more than random. See the criss-cross? Any ideas?
 
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As a result of the leakdown test, we determined air was escaping through one or both valves and coming out of the spark plug hole of the adjacent cylinder. So, in the 4 weaker cyls the valves weren't closed completely when the piston was at TDC. It would seem only 2 possibilities for this: deformed valves or the camshafts being slightly off.

Could this be a timing issue?

Could the camshafts on both banks being slightly off cause the valves to not seat correctly? How would this happen.......stretched belt, or both cam pulleys being off 1 tooth? When I put the timing belt on after checking my idler/tensions bearings, I spun the crank 3 times, and the marks were perfect each go 'round. Besides, the motor runs the same as it did before I messed with the belt. So I don't know how the belt could be off 1 tooth on each pulley.

My shop manual talks about removing/replacing the timing belt, and it gives the timing as 10 degrees BTDC, but says nothing about how to "set" the timing, like on a car motor with a timing light. Do I need to break out my timing light? But how?

I don't know. I'm just throwing things out there before I spend a lot of time removing the heads.
 
You're deeper into that engine than I have ever been, so I can't be of much help.

That is an interesting theory about the timing and I think you should go down that path before removing the heads. If the top of the compression stroke is not properly sync'ed with the valves, that could very well explain your compression numbers even though the values are functioning properly. One question - how did you determine that each piston was at TDC when you did the leak down test? If you were doing that from the cam position and the cam was off, that could explain your leak down results. Maybe it would give you some insight if you align your compression results with the engine's firing order (which I cannot find in the Helm manual, although I think it's in there someplace.)

Once the timing belt is correctly in place, the ECM handles the timing. You don't set it like in the old auto engines. (Are you telling us your age??? LOL)

Since you are likely going to replace the timing belt anyway, why not start with a new belt? Re-set everything and repeat the leak down test. And this time if you get air escaping through the valves, you might try moving the cams left and right a bit to see if the results improve.

Just some thoughts on a screwy problem.
 
chawk_man said:
One question - how did you determine that each piston was at TDC when you did the leak down test?
Click to expand...

Chawk.....my mechanic used a long screwdriver and a remote starter switch to bring the piston up close, and then I used a breaker bar on the crankshaft pulley to move it until he said it was right. We repeated the test twice, with the same results. And the leakdown results related as one would predict to the comp numbers. So, I'm comfortable believing that the valves aren't fully seated at TDC. The question is why?

If it were just one bank, I'd immediately suspect a camshaft problem. But both banks acting screwy? Doesn't add up.
 
OK, that sounds good to me based on my distant experience with auto engines.

I guess the way I would approach this is to first replace the timing belt and check compression and leak down again. If that doesn't fix it, then remove the valve covers and do a really detailed inspection of the cam, upper valves, valve springs, etc. while mechanically turning or cranking the engine. Look for anything that's not right. Re-do the leak down test with the valve covers off and see if that helps pinpoint the issue. Then as a last resort, pull the heads.
 
You need to make sure all timing marks are aligned. ...including crankshaft pulley. One notch pff can give you wacky readings.

Mike.
 
hondadude said:
You need to make sure all timing marks are aligned. ...including crankshaft pulley. One notch pff can give you wacky readings.

Mike.
Click to expand...

I checked the marks again today and they're dead on for all three pulleys. Just out of curiosity, I jumped the belt 1 tooth on the cam pulleys. That put the marks so far off that it verified I had them dead on in the first place.

I got as far as one exhaust manifold. I'll get the heads off tomorrow. One thing very interesting is that the exhaust anodes are 98% gone. No other corrosion to be seen in the one manifold off so far.
 
Are the valves adjusted properly? There is a certain sequence for this. Improperly adjusted valves will give you similar results in your leak down test. I would replace belt with new belt like Chawk says..also check all those tensioner pulleys, If you remember I just got fu#$@^ on one of my motors cuz of this. Ive been too busy to tear into it. Then adjust the valves like the book says and do your leak down test...if results are same pull cylinder heads. Also keep in mind that a brand new, not remanufactured block from boats.net with pistons, bearings, no heads is about $3200, which I find very reasonable in comparison to spending $19K
 
Here's an update, guys: I got the heads off 2 hrs ago. Easy job, as long as you have a beast breaker bar. As you can see in the images, these valves remain heavily carboned up, even after a shock treatment of both Ringfree and Seafoam. Quite a bit of carbon remains on the top of the pistons as well. My assumption is that this motor was extraordinarily loaded with carbon when I bought it. I know the decarb treatments must have removed at least some.

I wasn't able to get a good image of inside the cylinders. There was no scoring, but there were also no cross-hatch marks to be seen. And there were noticeable wear patterns on the bottom of all cylinders, as if gravity had caused the downward side to wear a little more than the rest.

My mechanic thinks the lack of cross-hatching is something to be concerned about, but if this indicates worn rings, why do I have 2 strong cylinders, 205 and 185?

I'm not going to put a new short block on a 12 year old motor, nor do I want to rebuild the whole thing. So my options are limited to just reconditioning the heads and slapping them back on with new gaskets. I feel like if I can get my weak cylinders up to 170 and get another 1,000 hrs, I'll be happy.

So what do the pros think about this lack of cross-hatching? And all this carbon, on a motor with approx 850 hrs? Help at this point is greatly appreciated......thanks.
 

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Good to hear it was relatively easy. Did you do any special prep or use an impact driver?

I'm definitely not a pro this deep into the engine and my knowledge of that was working in my dad's garage for about 10 years in my teens (which was really a long time ago.)

Like your mechanic, I'd be concerned about not seeing any cross-hash marks. It's my understanding that they are essential for proper lubrication of the rings. However, given the tight tolerances in all Honda engines, I suspect they are not nearly as pronounced as you would see on the older auto engines. Just speculation. Hopefully one of the folks on this forum who have a lot of experience tearing down these bigger Honda's will jump into the discussion about the cross-hashing. One thing I would definitely do is to measure the bore to see if it is anywhere near specs and check the roundness. If that checks out, then your strategy of just rebuilding the heads seems appropriate.

The BIG question is why all of the carbon buildup? Speculation again - all low speed operation, like trolling; a failed HO2 sensor for an really long time; a lot of really bad fuel; few oil changes (i.e. very dirty oil - which could also explain the worn-off cross hashes); an ECM not properly making fuel and timing adjustments. I suspect that given your compression numbers, the carbon buildup fed on itself over time.

For folks following this thread, these pictures make the case for running the engine out a near WOT for extended periods and for regularly using a de-carb agent in your fuel.
 
chawk_man said:
Did you do any special prep or use an impact driver?
Click to expand...

If you mean for the head bolts, I just used a 24" x 1/2" breaker bar. I tried the smaller stuff and forget it.

I didn't run into any problems dismantling, such as corroded bolts, thank God. I left the intake manifolds on the heads. The whole unit slipped right out with a little help from a screwdriver to separate the gasket seals.

If I had the motor in a home shop, with workbenches and such, I'd rebuild it. But my boat is in a dry stack, so parts just accumulate in plastic bags under the boat. Not my favorite setup.
 
It sure looks like you had a water intrusion problem on cyl 1 and 2. Did you have corroded head gaskets? I'm wondering if the introduction of water into the cylinder could cause valves to slightly bend and cause the loss of pressure,thus the carbon increase..just a thought.
 
Skooter said:
It sure looks like you had a water intrusion problem on cyl 1 and 2. Did you have corroded head gaskets? I'm wondering if the introduction of water into the cylinder could cause valves to slightly bend and cause the loss of pressure,thus the carbon increase..just a thought.
Click to expand...

The gaskets looked good and no corrosion and/or rust to be found, other than some salt, scale in the water jacket. No corrosion in the cylinders.

I just did some studying up on the Web about cross-hatching. It seems Honda goes with a very fine CH from the factory. I will look closely at the tops of the cylinders, where the rings don't get to, and try to see CH. First glance shows no lip. But make no mistake, the walls look pretty smooth, as in not much if any CH left.

This didn't stop the 2 strongest cylinders from making 185 and 205psi cold, before the Seafoam treatment. Seeing as how there is so much carbon on the valves and on the piston tops, I can imagine the possibility of significant carbon still down in the rings.
 
I agree that given the way the valves look, you likely have a pretty good carbon build-up in the ring slots. Since that is an age-old problem, there's likely some solutions out there in cyberspace for loosening up those rings without removing the pistons. If push comes to shove - a direct application of Sea Foam may do some good. Let it sit in there for several days and flush it out. That would have the added advantage of cleaning up the tops of the pistons.
 
One thing I was wrong about: the anodes were not gone. They were covered in scale. Once cleaned, they were about 90% good. So I'm not changing them.

Since corrosion seems virtually non-existent in the water jacket (anywhere internally for that matter), I'm going to get the heads re-conditioned and slap them back on. If I can get another 1,000 hrs, I'll be happy.

I have 4 cyls that are 165psi or above, right now, before the heads. If I can get all of them above 170psi I'll take it.

While I'm waiting for new parts, I started the Seafoam treatment directly in the cyls to loosen the rings. The motor is tilted all the way up. I filled the cyls yesterday, and I'll check them today. I don't see any reason not to do this repeatedly for several days. Gradually the SF will seep past the rings, so I'll have to refill.

One automotive mechanic who specializes in rebuilding motors and has done hundreds, looked at the cyl walls. He suggested that what looks like wear pattern might instead be "flow" pattern, due to the injectors and/or exhaust gases. Another mechanic friend checked roundness yesterday while I wasn't there. It will be interesting to see the results.

The heads will cost $425 for the pair, not including any valves or guides that have to be replaced. I supply the seals. This includes pressure-testing, grinding, milling, checking the camshaft, and adjusting the valves. Seems like a fair price.
 
Yes, I agree that seems to be a very fair price for reconditioning the heads.

With the sea foam in there on the top of the pistons, it would probably be a good idea to rotate the crank shaft a half turn or so about twice a day to help the Sea Foam get around the rings.

All of us following this thread will be interested in how the roundness test comes out. If that comes out well and within specs and you get those rings loosened up, You should get really good compression once it's all back together.
 
Have you checked that the crankshaft end-float is within spec ?
Just wondering if a failed crankshaft thrust bearing is the cause of your cylinder wall bottom wear e.g. crankshaft dropped down and putting downward pressure on con-rods and pistons.

Bob
 
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