Compression on 1997 Johson Oceanrunner 150 HP

[fishmstr]

A boat broker interested in my boat checked the compression and all cylinders were about 93. He said it was good that they were all the same but that it was way too low. Would it be worth getting a 2nd opinion on the compression? I watched him do it and read about doing it and I think I can borrow a tester and do it myself, if I can get someone to turn it over for me. I've heard that gauges don't all read the same and some can be off quite a bit. This guy did a warm engine test but is coming back to do a cold test.

I asked the guy if he would trust the engine enough to go fishing and he said, "I wouldn't go offshore." It runs like a scalded dog. I would have never thought it was on it's last leg. The biggest reason this guy could come up with is that the boat sat for 8 months while only getting run every 2-3 months.
What do you think?
Thanks

 

[iwombat]

Re: Compression on 1997 Johson Oceanrunner 150 HP

I think anything over 70 represents a motor in very serviceable condition. If it's got compression in the 90s and it runs poorly, it needs a decarb, tuneup, and probably carburetor work. Then, i'd run it without worry.

I'll let the others weigh in on compression number though.

 

[iwombat]

Re: Compression on 1997 Johson Oceanrunner 150 HP

Maybe you could describe how he did the compression test.

Did he remove _all_ the plugs and spin the motor up to at least 400rpm or so?

If not, it's gonna read low.

 

[fishmstr]

Re: Compression on 1997 Johson Oceanrunner 150 HP

He took all the plugs out and used a screw in gauge. He had his helper turn it over for about 3-5 seconds. I watched the gauge and saw the numbers. It got up to the low 90s pretty quick but once there, he didn't let it keep going much. Seemed like it was topping out at that point. Don't know about the rpms for sure.

Thanks

 

[iwombat]

Re: Compression on 1997 Johson Oceanrunner 150 HP

Sounds like he did it right.

The lower the compression, the higher you'll have to set the idle to keep it from cutting out. You'll lose a bit of power as well. Other than that, no reason this thing shouldn't purr right along.

 

[OBJ]

Re: Compression on 1997 Johson Oceanrunner 150 HP

Find another broker, fish.

 

[iwombat]

Re: Compression on 1997 Johson Oceanrunner 150 HP

Just for reference, I've got an 85hp that reads numbers a couple of PSI lower than yours. Runs like a top and idles smooth.

 

[Dhadley]

Re: Compression on 1997 Johson Oceanrunner 150 HP

Again I find myself agreeing with OBJ. I'd bet the motor's fine. If he doesn't trust it let him discount it to you. If it idles OK, that would back up my suspicion everything's OK.

If he talks you out of it, let me know. I got family in G-ville. Be a good excuse to go see them.........

 

[fishmstr]

Re: Compression on 1997 Johson Oceanrunner 150 HP

Sorry I wasn't clear, this boat is mine and I'm trying to sell it. Sounds like the broker's going for broke and trying to get me to discount it more to him than I planned on. It idles great and starts wtihout fail. Thanks for the input everyone.

 

[BF]

Re: Compression on 1997 Johson Oceanrunner 150 HP

as you said, compression testers can vary one to the other... being a cynic, it wouldn't surprise me if he's got a "shopping for a boat" compression tester, and a "selling a boat" tester. It could save him some cash if the vendor is always seeing compression numbers that are 10% low... but like I said, I'm a bit cynical.

So yes, I'd go buy one yourself and see what your numbers end up as.

 

[Walker]

Re: Compression on 1997 Johson Oceanrunner 150 HP

Get a guage and do your own test like suggested. Then fire the motor up and let it warm up and do another test.
#93 sounds fine to me.

 

[iwombat]

Re: Compression on 1997 Johson Oceanrunner 150 HP

Either way 93 is hardly a motor on its last legs.

 

[fishmstr]

Re: Compression on 1997 Johson Oceanrunner 150 HP

Thanks for all the help folks. One more stupid question, I want to get my own compression tester. What size thread to I need? Most come with at least 14mm and 18mm adapters. I'm guessing 14.

 

[Walker]

Re: Compression on 1997 Johson Oceanrunner 150 HP

Whatever size the sparkplugs are. I think they are standard thread not mm, could be wrong, I never measured one.

 

[Dhadley]

Re: Compression on 1997 Johson Oceanrunner 150 HP

They are 14mm threads.

 

[reeldutch]

Re: Compression on 1997 Johson Oceanrunner 150 HP

ask your broker what compression nrs he accpected to see?

i bet you he knows its in good shape as long as the nrs are even.

and when you do a cold test it will tell you a different story and i think it will go up above 100.

on the other hand a lot of people like to see high compresion nrs.
so it might sell easyer for him if it was higher.

 

[DHPMARINE]

Re: Compression on 1997 Johson Oceanrunner 150 HP

As OBJ said,get another broker. hopefully one who knows more.Johnson/Evinrude V6 engines don't usually show more than 95 PSI in a compression test.You may be getting reeled in (in this case).Be real careful.

Also,when I do a compression test,I have a spark tester on the plug wires,and use a remote starter button.Don't really need someone to turn the key.

What is going on in your case doesn't sound professional.

DHP

 

[fishmstr]

Re: Compression on 1997 Johson Oceanrunner 150 HP

Thanks to all. Hopefully, I will check it with my own tester tomorrow.

 

[fishmstr]

Re: Compression on 1997 Johson Oceanrunner 150 HP

Tested it with my own tester todaty and got about the same readings, on a cold test, which he wants to do tomorrow. Very consistent among cylinders, in the 92-95 range. Didn't have time to do it warm today. I would assume it would test lower psi cold and he tested it warm. I'll see if he'll use my tester tomorrow when he comes back. At least know, I have some ammunition to counter his concerns with, like great idle and consistent pressure among cylinders. Thanks again folks.

 

[DHPMARINE]

Re: Compression on 1997 Johson Oceanrunner 150 HP

To quote OBJ and myself,get another broker,fish.

DHP

95 psi is not a bad reading on an OMC V6