Can some give me advise

stoked not

Petty Officer 2nd Class
Joined
Jul 20, 2001
Messages
143
I'm about to do a deal on a boat that has a 1991 225 HP Johnson. Befor I hand over the cash I'm going to check the compression. Can anyone tell me what the compression should be? Can anyone tell me about this OB. Godd or bad.<br />Thanks<br />Stoked
 

stoked not

Petty Officer 2nd Class
Joined
Jul 20, 2001
Messages
143
Re: Can some give me advise

Specs and Reds,<br /><br />I'm no expert on OB's and I didn't even stay in a Holiday Inn Exspress last night. But I thought low compression was an indication of bad rings. Mabey I'm way off.<br /><br />Stoked not
 

stoked not

Petty Officer 2nd Class
Joined
Jul 20, 2001
Messages
143
Re: Can some give me advise

Specs and Reds,<br /><br />I'm no expert on OB's and I didn't even stay in a Holiday Inn Exspress last night. But I thought low compression was an indication of bad rings. Mabey I'm way off.<br /><br />Stoked not
 

Cricket Too

Lieutenant Commander
Joined
May 14, 2003
Messages
1,732
Re: Can some give me advise

Stoked....Low compression is a sign of alot of things, bad rings being one, but what Specs is saying is that all 6 cylinders should be pretty close in compression to one another, if one is alot lower than all the rest or two are then you know there is some type of problem. If they are all the same, whether it be 100 or 120, then you are good. If all were too low it probably wouldn't run, and I doubt that that would happen, usually one or two are low and the rest are good, if there is a problem. It will probably be O.K.. Let us know what the test tells you. Good Luck.
 

stoked not

Petty Officer 2nd Class
Joined
Jul 20, 2001
Messages
143
Re: Can some give me advise

Hey Guys,<br /><br />Just got a call from the seller with compresion readings. (of course I'll do my personal check too)<br /><br />Here's what he said the radings are. What do you think?<br /><br />Cyl#1 90<br /> 85 <br /> 85<br /> 85<br /> 84<br /> 84
 

Hooty

Rear Admiral
Joined
Oct 2, 2001
Messages
4,496
Re: Can some give me advise

Tough call. The compression readings are low. That could be an indication of worn rings or they (the rings) could just be coked up, which a good decarboning would fix. I'd see if the owner would agree to a decarb and then see what the compression readings are. Use the search function here on iboats and do a little research on "decarb". Doesn't cost much or take long to do.<br /><br />c/6<br /><br />Hooty
 

stoked not

Petty Officer 2nd Class
Joined
Jul 20, 2001
Messages
143
Re: Can some give me advise

Hooty,<br />Thanks for the tip on decarb. Did a search on decarb but I'm not sure how this is performed. Can you advise.<br />Thanks<br />R/<br />Stoked not
 
Joined
Jun 15, 2003
Messages
65
Re: Can some give me advise

If you use a decarb product in an aresol can, the instructions like on most products are on the can. <br />Basicaly, I've heard a can per cylinder is a good measure, and you simply spray the product into the carb/ throttle body (with engine at idle to fast idle) until the can is done. Turn off the engine and let it sit overnight (reconmended sit time is posted on the can) <br /> Then start it up and run the motor for at least 30 min to get all of the product out. (it's even better if you can do this at the water, and do water-runs to clean the engine out. The product isn't harmfull to the environment...i think)<br /><br />Good luck
 

nitsuj

Chief Petty Officer
Joined
Jul 22, 2003
Messages
483
Re: Can some give me advise

The fact that they're all low and fairly consistent would make me wonder if the check was performed correctly. I'm not an outboard expert, but I am an ex motorcycle tech. On a bike, if you don't hold the throttle wide open, you'll get a low reading. I can only assume it's the same on an outboard motor. I checked the compression on my Johnson today, all 4 were 105 on the nose. If just one of the cylinders was low on your motor, I'd think maybe bad cylinder, but if all of them read low, and within a pound, it seems like a pretty good coincidence. Maybe one of the gurus will either agree with me, or shoot me down.
 
D

DJ

Guest
Re: Can some give me advise

stoked,<br /><br />The readings being low can be from coked up rings.<br /><br />However, my money is on the procedure not being done correctly.<br /><br />Use your own guage and put the throttle at wide open before taking the readings. Ignition disabled-of course. Pull the kill lanyard.
 

stoked not

Petty Officer 2nd Class
Joined
Jul 20, 2001
Messages
143
Re: Can some give me advise

Hey guys,<br />Thanks for all your post. I real piece of mind for me. Here's the boat I'm buying what do you think. web page <br /><br />Now if I can only sell me other boat.<br /><br />Stoked Not
 
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