Buying a used motor

[Seattleflyfisher]

It's more then a compression test. We have another member here hot to trot to buy a motor. He has been burned lately and he did just do a compression test on a motor up north. I spoke with him tonight and he did another test to find out the motor was bad. In the last 3 months we have also had a member up North get burned on a used motor. I will not say the members name ( Jeff ) .......hello!

Please help out here with what you are testing and what you have seen.

For me! I have also been burned with motors. I would hope we all could help each other here on what they are seeing and doing to check motors out before buying.

SFF

[StreamFixer]

Buying motors is scary, on a boat or off.  At least for me.

I am willing to spend the couple of hundred $$  and have a pro check it out before I spend thousands $$$ on a maybe.  Same as I do with cars.

StreamFixer

[Vancouvertechie]

Like anything out there you can get burned.  Though I agree with SF on paying a couple hundred, but what if the motor is just a couple hundred dollars?  As for me on 2-strokes compression testing and spark are the key indicators.  I think I have bought a new motor once on my 14' RIB.  All the rest have been used motors on a used boat.  Since I don't own a new Arima I go with used.  Plus, I am aiming to retire in 10 years at the ripe age of 52.  Get busy living or get busy dying.  Enough about me.  Here is what I look for when motor shopping the used stuff.

Look at overall condition - Physical appearance means something.  ie, rust, lose bolts, scratches and what not.

2-Strokes
Check compression with my tester
Check spark with my tester
Check ohms with my tester (stator)
Check lower end oil
Check propshaft for any play
Check waterpump output
Run test

4-strokes
Check compression
Check waterpump output
Run test if possible boat test

It's not that I don't like working on motors, but I am very, very cost minded.  It is not how much you make, but how much you spend.  Plus cancer treatments add up.

[jcheech]

Darren! I said no names on this site, then they'll know it was me (Jeff). Yes I have been burned and it hurts.

I would like to add my  :twocents:. In addition to the recommendations above I would strongly recommend doing a Leak Down Test, even more so than a compression test. Essentially it measures the amount of air a cylinder is able to hold and can detect air leaking past a cylinder, a blown head gasket or improperly seating valve. I just recently used it to test a yamaha 115. The motor had decent compression and ran well. I did the leak down test and found that 2 of the 4 cylinders had over 30% loss. Not good. I have read that anything beyond 15% leakage is a serious concern. Had I only done a compression test I would have been stuck with quite a mess (again).

I recently (today) purchased a boat with a yamaha 115. Again, I tested each cylinder. No more than 2% loss in each cylinder. Good times.

Here is a good article that made me buy a leak down tester:

http://www.catfish1.com/forums/showthread.php?t=162691

Tools needed:

Leak Down Tester   $70  http://www.amazon.com/OTC-5609-Cylinder-Leakage-Tester/dp/B0030EVL60
Basic Air Compressor
Air Hose
Socket Wrench for removing Spark Plugs
Pair of leather gloves (for holding the flywheel at cylinders TDC)

Crude Instructions (find a good tutorial online)

Remove spark plug
Find cylinders top dead center (you will need to find a way to secure flywheel in place at or very near TDC)
Thread Tester Hose to the spark plug hole
Connect to Leak Down Tester
Connect Leak Down Tester to compressor hose
The gauge closest to the compressor will show the regulated air coming in
The gauge closest to spark plug will show the amount of pressure lost
So if you set your first gauge to 100 psi, and your second reads 90 psi you have around 10% loss

Once pressurized excessive loss could be worn or damaged piston rings (air coming out of the oil cap), improperly seating valves (air coming out the exhaust or carb manifold), blown head gasket or warped block (air coming out everywhere!!!). Well maybe not but you get the idea. I haven't set my first gauge to 100 psi due to the fact I haven't found a great way to secure the flywheel. I set the first gauge to 50 psi (which I can hold) subtract the amount of the second gauge and x by 2 to get my percentage of loss (my brain has to keep it simple). When I go to check out a motor, I load up the compressor, air hose, extension cord, etc.

Please consider this test if you plan on buying a 4 stroke. Do some research and find better instructions than I provided. Saved me big $$ for a small investment. I'm nowhere near being an expert with any of this stuff. I'm a cheapskate and usually know just enough to get me in trouble. Feel free to PM me with any questions.

Thanks,

Jeff

[Hydro-Therapy]

 

Jeff so you are the lucky dog that got that sweet setup, boat and all the fancy gauges. Did I see it right that it did have hydraulic steering also ? Congrats on the fine catch,

   H-T

[amazing grace]

I recently bought a Honda four stroke 115hp from a member who was going to a 90hp on his 17' Arima. With low hours and known history.
In general mid range four strokes scare me a bit. Especially older ones. The 90's and early 2000's. Not that they can't be good motors, but I would definitely get them checked out thoroghly and not  over pay for them. Just to much risk for me.
Now two strokes I like and because they cost a lot less. Are less technical. And seem to run a long time, I personally associate them less risky than an older four stroke. I know some will disagree.

I have a Yamaha 115hp two stroke sitting in my shop looking for a boat? :dance:

[jcheech]

H-T,

Thank you I feel very fortunate. The whole buying experience was pretty cool. After receiving notification from the arimaowners emergency purchase network I contacted the seller who was a first mate on a on a luxury motor yacht. We set up a time for 7am. I was then able to find a trailer at 10:30 that night off craigslist for $350. Met him at 5:30 AM for the pick up then off to the boat. The 150 yacht was in dry dock being repaired in a huge facility. Everybody was great. Met the captain and hung out with the crew, had a cup of coffee and some snacks. If I was 20 years younger I might have hopped aboard. The yacht cruises the pacific rim chasing the summer and hitting all the best diving spots. It's good to be a billionaire I guess. Anyway, yes you are correct, it does have baystar with the tilt steering wheel option and digital gauge package. The boat is a complete custom package they had made to fit a specific spot on the yacht. The 115 checked out pretty much perfect with only 220 hours. I can safely assume I will never have a buying experience like that again.

Jeff

[wedocq]

Jeff,
A leak down test done properly does give a very good indication of the wear and tear on a motor. It's important top dead center is precisely found for each cylinder, or you may receive false readings! Along with a compression test, it can give a pretty good picture of an older and or high hours motor's health. Here is a chart a found that generally describes what each percentage of loss means:

1. Less than 5% - You either did something wrong or have one hell of a nice tight engine.
2. 5% to 10% - Great to good. You should have no worries.
3. 10% to 20% - Your motor may still run ok, but it isn't at it's best. Parts may be starting to wear out....keep an eye on it and test it more regularly.
4. 20% to 30% - It may be (and probably is) time for a rebuild.
5. Greater than 30% - You have some major engine issues that need to be addressed.

Other things I look for when buying:
1) Engine oil condition. Fresh oil makes me a little nervous. Is he hiding something? Dark black oil makes me nervous as well. How often does he change it?
2) Lower unit gear oil condition. If it comes out milky, water is getting in. If water is getting in, internal damage may have already occurred. At the very least, seals will need to be replaced.
3) How well is the water pump working? Good pee stream? Using a infrared thermometer, are you finding any hot spots? It could indicate salt build up.

-Shawn

[GregE]

Bump
You guys just cost me more $$...   

[StreamFixer]

I'm pretty sure I feel bad about that.  Let me check and get back to you   :biggrin:

StreamFixer

[croaker stroker]

A friend of mine answered an ad for a boat with an older engine. The ad said that there was no compression in one cylinder. He bought the boat at a significantly reduced price. When he got it home, he went through it and cleaned the system out with Sea Foam. A compression test showed good compression in all cylinders. 


It's always a gamble when you buy a used motor.   

[ohmytodd]

My new to me '04 Honda 150 showed 160 (130 the first time), 190, 190, 175, so I fully expected to need some serious work done soon (and got a price to allow for it). My local mechanic treated the cylinders overnight with Ring Free and retested it. 210, 210, 210, 200.

You just never know.