Compression test readings-work order

[Msp381]

I’m looking at a 2008 Freedom and the Yamaha 250 was just serviced. This is what had to be done and as you can see the compression seems low to me. Of course the range is exactly within 10% acceptable. Based on what you read here would you simply pass on this or have a leak down test and continue with negotiations? It has 445 hours on it. I did see a pic of the exhaust looking for dry exhaust corrosion and it appears very clean.

 

[Hookup1]

Maybe a few members will venture an opinion. Helpful but I would try for an expert opinion. Find a mechanic that works on a lot of engines. Easier said than done though.

 

[SeanC]

That does seem low. I recently did a cold compression test on my 2006 F250 with 1450 hrs. 5 cylinders were 175 psi and one was 170 psi. Have always run Yamaha Ringfree in the fuel. You might want to try a Ringfree shock treatment to see if the low values are due to carbon buildup.

 

[igblack87]

My 2006 250 has 190 psi in all cylinders...if your looking for comparison. 775hrs on the motor.

 

[seasick]

How did the boat itself look?
I ask because my first impression of the service report leads me to suspect that the motor was not well maintained. Usually when a hull is not maintained, neither is the engine..
I am also at a loss to explain why the compression was lower in all three even cylinders. That could potentially indicate a serious issue or It could just be a testing fluke.I would have really liked to know the he condition of the old spark plugs. The exhaust issue is not common on 2008 model and later motors.
The report didn't mention if the LU oil looked bad.
The gunk in the water jackets could mean that the motor was not flushed often enough or at all after use.
The frozen broken off bolt is common but it can mean that the thermostat had not been replaced in a while, maybe never before this service.
My guess is that the motor was run hard and not well maintained. The ECM dump rev report may help determine how hard the motor was run

 

[basspirate]

Those numbers being low all around dont indicate bad head gaskets or a valve problem. Bad Head gasket would give you 1 or 2 low cylinders. 1 if the leak was on the outside of the gasket. 2 if the leak was where the cylinders met. A bad valve would usually be isolated to 1 cylinder unless there was a timing problem. I.e. the belt jumped a tooth but that is rare and the engine would run crappy.

I believe you have a few different things possibly going on. Either the mechanic used an un calbrated gauge, which does happen pretty often or you have stuck rings. Its also possible that the engine was poorly maintained/ and or had a lubrication problem. I would skip the leak down and get a second compression test done by a different mechanic. Also try to find a mechanic with a boroscope. Have him look in the cylinders to see if there is still cross hatching and if there are any gouges in the cylinder walls.
If the owner does not let you do these things, i would run away.

 

[Hookup1]

I assume that work order was paid for by the current owner. Must not have thought the differences in compression numbers would not be a problem. Now you have various opinions and have to figure out who is paying for this additional investigative work. Compression re-test, bore scope and leak-down. Might as well know what you're in for if you go ahead.

 

[Msp381]

I assume that work order was paid for by the current owner. Must not have thought the differences in compression numbers would not be a problem. Now you have various opinions and have to figure out who is paying for this additional investigative work. Compression re-test, bore scope and leak-down. Might as well know what you're in for if you go ahead.

Thanks everyone! The boat hull and inside is spotless! I too am curious and asked for the print out of rpms it was run at. I will have a second mechanic check it out.

 

[Hookup1]

I thought it would be fun to see what all this AI noise is about....

Hookup1: What should the pressure be for a compression check on a yamaha 250 hp outboard

OpenAI: The specific pressure reading for a compression check on a Yamaha 250 hp outboard can vary depending on the exact model and year of the engine, as well as other factors such as the altitude at which the test is being performed.

As a general guideline, the compression pressure on each cylinder of a Yamaha 250 hp outboard should ideally be between 100-150 psi (pounds per square inch) with no more than a 10% variation between cylinders. If the compression pressure is lower than this range, it may indicate a problem with the engine's piston rings, valves, or other components.

Hookup1: Compression results 150, 135, 150, 135, 150, 135 for each cylinder

OpenAI: Based on the compression results you provided, it appears that the compression pressures on each cylinder of your Yamaha 250 hp outboard are within an acceptable range. While there is a slight variation between the highest and lowest readings, this is still within the range of 10% difference that is considered acceptable.

Hookup1: Should a leak down test be performed

OpenAI: A leak down test can be a useful diagnostic tool to help identify potential issues with an outboard motor, especially if there are concerns about low compression or other performance problems.

In a leak down test, compressed air is introduced into each cylinder while the engine is at top dead center (TDC), and the amount of air that leaks out is measured. This can help identify problems such as worn piston rings, damaged valves, or leaking head gaskets.

While a compression test can provide an initial indication of the overall condition of an outboard motor's internal components, a leak down test can provide a more detailed evaluation of the specific areas that may be causing low compression or other performance issues.

 

[basspirate]

Its almost as if the ai regurgitated generic talking points off this thread.

All the low cylinders are on 1 side of the engine (port side?). Any overheating in the logs on one side? Also any water in the oil?

 

[Hookup1]

Its almost as if the ai regurgitated generic talking points off this thread.

I fed OpenAI the questions from this thread. I'm sure that's why it looks like its repeating it back.

This is a generic AI chat. It was not trained to answer specific questions about Yamaha outboard motors. It didn't find anything you couldn't find searching the internet yourself. It just did it much quicker. It does organize your questions into a conversation and knows the context of the next question. Clearly didn't have any "experience" with the subject - just what it read.

 

[Ky Grady]

Here's compression numbers on the cylinders.

1 = 190
2 = 191
3 = 191
4 = 190
5 = 190
6 = 190

Actual hours are a little less than the gauge.

Gauge was 1384
Actual hours 1317

This was from my 2004 F225 when I sold it back in January for my repower. Certified Yamaha service dealer in Charleston SC. Those compression numbers do seem low given the low hours on the motor. As others have said, a heavy dose of Ring Free run through it could bring those numbers up.

 

[family affair]

Have you done a seatrial? If the boat prop is original and not reworked or damaged, the boat should be able to hit the wot numbers in the performance report. Grady will email this to you. If it doesn't, then your compression test isn't lieing.

 

[seasick]

I always state that if a boat looks like it wasn't taken care of, the motor probably wasn't either. There is another side to my argument and that is if a boat that is as in this case 14 years old, looks pristine and it is a brokered boat, it probably was detailed. That is not necessarily a bad thing but detailers can be really good at hiding issues, especially with the hull and the upholstery.
Back to the compression numbers: The fact that all three cylinders on one bank have low compression may mean that there may be a jumped timing belt.
I am very suspicious by nature and that contributes to my paranoia. There is just something with this boat that makes me feel uneasy

 

[Msp381]

I always state that if a boat looks like it wasn't taken care of, the motor probably wasn't either. There is another side to my argument and that is if a boat that is as in this case 14 years old, looks pristine and it is a brokered boat, it probably was detailed. That is not necessarily a bad thing but detailers can be really good at hiding issues, especially with the hull and the upholstery.
Back to the compression numbers: The fact that all three cylinders on one bank have low compression may mean that there may be a jumped timing belt.
I am very suspicious by nature and that contributes to my paranoia. There is just something with this boat that makes me feel uneasy

I have not sea trialed it yet. Mechanic also said he did not and it was simply brought in for the service. Sounds like a sea trial is what’s needed. Thanks to everyone for the responses.
I talked to a Yamaha technician and I was told anything above 80-90 psi…don’t like that idea.

 

[Msp381]

I have not sea trialed it yet. Mechanic also said he did not and it was simply brought in for the service. Sounds like a sea trial is what’s needed. Thanks to everyone for the responses.
I talked to a Yamaha technician and I was told anything above 80-90 psi…don’t like that idea.

A response I received from a mechanic was the the heads may have been milled different thus the reasons for the low compression. Any truth to this?

 

[basspirate]

That is a definite possibility however i highly doubt that would be from the factory. It is possible that the heads were removed and milled. The machine shop may have had to take a few thousandths more off one side. Any signs of the bolts being removed? Scratches on the paint, or wear marks on the bolt heads? Does the head gasket have paint on it or does it look like its been replaced?

 

[Msp381]

That is a definite possibility however i highly doubt that would be from the factory. It is possible that the heads were removed and milled. The machine shop may have had to take a few thousandths more off one side. Any signs of the bolts being removed? Scratches on the paint, or wear marks on the bolt heads? Does the head gasket have paint on it or does it look like its been replaced?

I have no idea. I currently am not near the boat and am trying to determine if this is worth the drive. By the sounds of it, it’s not worth it.

thanks everyone, I’m going to pass.

 

[Ky Grady]

I have no idea. I currently am not near the boat and am trying to determine if this is worth the drive. By the sounds of it, it’s not worth it.

thanks everyone, I’m going to pass.

Probably a good choice. Seems to be to many variables in what would cause low compression.

 

[Hookup1]

I have no idea. I currently am not near the boat and am trying to determine if this is worth the drive. By the sounds of it, it’s not worth it.

thanks everyone, I’m going to pass.

I think that is the right answer. Especially if the boat is far away. Too hard to properly evaluate what you are buying. There are more fish in the sea!