Buying a used 50HP 4 stroke outboard - what to check?

speo

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Jun 2, 2015
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Hello, I am planning to buy a used 2008 50HP Honda 4 stroke outboard from a private seller (not dealer).

I have a compression tester, but based on my research, the compression test is not relevant for 4 stroke motors, so I am planning to order a OTC 5609 Cylinder Leakage Tester Kit and do a leakage test. IS that overkill, or is it the right think to do?

Beside leakage, I was planning to check the prop shaft to be straight.

I saw the motor today, but the plan is to go next week to test it. Today it started instantly and I was told the motor was not started since November 2019, when the outside temperature went below freezing (today we got few degrees above freezing).

What else should i check in order to avoid buying a motor that needs expensive repairs that are detectable.

Thanks,
Speo
 

GA_Boater

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Hello, I am planning to buy a used 2008 50HP Honda 4 stroke outboard from a private seller (not dealer).

I have a compression tester, but based on my research, the compression test is not relevant for 4 stroke motors, so I am planning to order a OTC 5609 Cylinder Leakage Tester Kit and do a leakage test. IS that overkill, or is it the right think to do?

Thanks,
Speo

I guess I'll throw my compression tester away. Now I'll have to test for even compression, blown head gaskets, burned valves and worn bores and rings some other way. Maybe I can read how on the Internet so I know it's true.

Seriously, 4 stroke compression testing is still valid for the things listed. Leak down testing is good, but a compression test can be done faster and will find a bad cylinder.

Other than the prop shaft and leaks - Pull the dipstick to look at the oil for not being too dark like it hasn't been changed in years, feel it between your fingers for grit and sniff it for a gas smell. Also pull the plugs to see if they are sooty from running rich and not real light tan like it's running lean. All the plug colors should be about the same and no water on the plugs. While the motor is running, listen for odd noises.
 

Mohawkmtrs

Chief Petty Officer
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Jan 13, 2010
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561
No need for a leak-down tester (overkill unless you're a mechanic and will be using it more than once).

The compression gauge will find a bad cylinder (that's when you walk away from that motor) while a leak-down tester will tell you WHY the cylinder is bad.
 

speo

Seaman Apprentice
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Jun 2, 2015
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Thank you guys, if that is the case, I will do a compression test and check for the things you mentioned.

One thing I noticed yesterday was that the motor started instantly, even if it was not started since last November. It ran smooth, but for some reason, I could see some vibration, especially in the lower end, even at idle. So, it wasn't a bent shaft, but what else could cause this? The seller said it could be the old fuel. We ran it only for a couple of minutes.

Again, thank you, your help is really appreciated.
 

GA_Boater

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OK. On a stand vibration is more apparent without the mass of a boat to dampen.

I don't know if this Honda 50 has the shakes. Some motors do and some don't but some vibration may be normal for this model.
 

speo

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Jun 2, 2015
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Thank you for the quick reply.

I did some research on the compression testing. Some people are happy with all cylinders around 120PSI, some at 170PSI. Also some people are mentioning an acceptable maximum 10% difference between cylinders, some are saying 15%.

Any advice on what should I consider unacceptable?

thank you!
 

GA_Boater

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I don't have a Honda or a manual for the compression numbers. I like to use 10% variance.
 

racerone

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A value of 120 PSI would not be good on a 4 stroke.----Make sure throttle is at least 1/2 open when doing the compression test.
 

boobie

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On a 4 stroke motor the only way to check the true condition of it is with a cylinder leak down test. We used these 50 years ago to check motors in a tune up shop I worked in. Yes, a compression gauge is best for a 2 stroke. JMO
 

speo

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Jun 2, 2015
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Thanks again for the replies.

Yes, the outboard was hooked to a water hose using the ear muffs.

I received the leak down kit already, so, maybe I'll do both, a compression test and leak down test. I have to pull my little Honda gokart 4 stroke engine that I winterized 10 years ago and start practicing.
 

speo

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Jun 2, 2015
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The deal fall through.

Last week, when I went to see the motor, the seller told me he does not know the number of hours on the motor, because he is not tracking that. Fair enough, but I had a feeling the motor has a high number of hours.

I took some pictures of the boat and yesterday, when looking at the pictures, I realized a discrepancy between the pictures I took and the pictures the seller took 3 day before and sent me.

The difference was...in my pictures there was a round hole in the dashboard, but in his pictures there was a gauge in that hole. Zooming in, the gauge was "Hour Meter". I could not distinguish precisely all the digits, but the thousands digit was not 0 or 1.

For me, this was enough to walk away.
 

GA_Boater

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Sounds like the hour meter broke some time after you asked about hours last week and viewing the boat yesterday. A very conscientious seller as he didn't want to sell you a boat with a bad hour meter. He deserves applause. :eek:
 

The Force power

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Sounds like the hour meter broke some time after you asked about hours last week and viewing the boat yesterday. A very conscientious seller as he didn't want to sell you a boat with a bad hour meter. He deserves applause. :eek:

He could of at least put a working one in, with the "similar" hours lol
 
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