not running right

janthonyb7

Cadet
Joined
Jun 15, 2002
Messages
10
I have a 1998 30 horse johnson outboard motor. the motor would not run but half way with the cowlin on. with the cowlin off it runs great. I cut a hole in the cowlin right in front of the carb. now if the motor sits for a day or two it runs like its not getting all the gas it needs. After about 15 minutes of running the motor, jerking and everything else, it starts running right but cut it off for an hour same problem. I have rebuilt the carb, the fuel pump, replaced all the fuel hoses, changed the plugs.i'm lost need help.
 

almost retired again

Chief Petty Officer
Joined
Feb 9, 2002
Messages
438
Re: not running right

Hi, <br />if your engine runs good with the cover off I would say that you have a engine to adapter gasket blown. That's the gasket right below the engine. If you have exaust under the cover the engine can't run too good off it's own exaust.
 

janthonyb7

Cadet
Joined
Jun 15, 2002
Messages
10
Re: not running right

THANK YOU very very much almost retired again. You are the only person to tell me about a possible blown gasket. Everybody told me and still tells me that I have carb problems. I know I do not. I have rebuilt the carb to absolute specifications, no mistake. I looked into fixing it myself but it would probably take me a month to do it. So, I will probably take to a mechanic. Thanks again for your prompt reply.
 

oldboat1

Fleet Admiral
Joined
Apr 3, 2002
Messages
9,598
Re: not running right

Almost retired has a good suggestion, and you might need to get a mechanics analysis. On smaller engines, I have pulled the engine to install the gasket (believe that is what almost retired is talking about).<br /><br />One or two things you might do first -- Check to see if there is exhaust under the cover (i.e., when you lift the cover off after the engine starts to act up). That will help with diagnosis. Additionally, you might be able to tighten down the engine yourself with a socket wrench and extension (if from the top). Consult a manual for location of the bolts, or pose the question here, but it might be sufficient to just tighten down the powerhead.
 

janthonyb7

Cadet
Joined
Jun 15, 2002
Messages
10
Re: not running right

oldboat1, I tried your options on my motor but to no avail. All the bolts were tight. Once the motor heats up for about 15 minutes it runs regular but at only half speed. When I take the cowlin off it runs normal. During its warming up period it runs kind of rough, once warm runs smooth. As long as I keep cranking the motor every 15 minutes or so it will continue to run perfect. If the motor cools off any back to the same problems. I feel that once it heats up it is causing something in the motor to expand stop whatever problem seems to be going on.Still stumped.
 

fireman 757

Petty Officer 1st Class
Joined
May 18, 2002
Messages
276
Re: not running right

Almost is right. Sounds exactly like an exhaust leak. That is where I would go first. The only other possibility is that your water pump impeller is weak and you are overheating a little at high rpms and the engine wants to shut down. Go with the exhaust leak first.
 

janthonyb7

Cadet
Joined
Jun 15, 2002
Messages
10
Re: not running right

Thanks for the replies on my problem. Can anyone give me some kind advice on if I should try to tackle this probelm myself or not? I am very mechanically inclined, I do all my own automotive work. The reason why I ask is at $40 to $60 dollars an hour I don't want to pay someone a whole bunch of money to fix it. Does anybody have a possible guess on an amount?
 

alcan

Commander
Joined
Dec 14, 2001
Messages
2,505
Re: not running right

Hi <br />If as you say, you have mechanical talents. Then yes why not go for it. The first thing to do is obtain a manual. Your model is fairly new so the library may not have the one you need. Wouldn't hurt to check. But $30. or so bucks ain't bad compared to $60- $80. perhr labor. You know the money realy isn't so bad, it's the three weeks wait in the shop that gets me. I'm not blaming anyone, it's just that time of year. Hey at your shop there is no garentee, but there is no waiting, your motor is always first. Another place to inspect for exhaust leak is the exhaust cover gasket. Also check to see that the bonnet is not grounding out a spark plug some how. Good luck and keep us posted on your progress.
 

janthonyb7

Cadet
Joined
Jun 15, 2002
Messages
10
Re: not running right

I appreciate all your replies. I am going to start trying to pull the power head off the motor friday. I priced the gasket for my motor and for $8.00 I'll give it my best shot at replacing it myself. Thanks again for the help.
 

janthonyb7

Cadet
Joined
Jun 15, 2002
Messages
10
Re: not running right

I am trying to replace the power head gasket. The book says I need a special tool to replace the water tube grommet, is this true? Or can I get away without having to purchase this special tool? Also, can anyone tell me an alternative to OMC Triple Guard Grease and OMC Moly Lube?
 
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