30hp with temp problem?

Greetings from Sweden,<br />I have a 30hp around 5-10 years old. It runs badly on the top cylinder when warm (after about 3-5 minutes). Cooling seems to work since water comes out fine from the nozzle. If I disconnect the cable from the sensor on the block just left to the top spark plug the motor runs fine on both cylinders.<br />If I measure between the sensor and the spark plug it grounds when problem and breaks when the motor has cooled off a bit (15-20 min).<br /><br />What could be the problem? How can I verify if the motor is actually running hot or not?<br /><br />Thanks in advance<br />-tsl-

Re: 30hp with temp problem?

Hello tsl....Strange problem. First time I've heard of a temp sensor causing a motor to run bad.<br /><br />First we need to verify that the engine is overheating. Even though the water may be pouring out the tell tale, the t-stat could be stuck closed. With the engine at idle and engine warmed up, you should be able to lay your fingers on the flat area on top of the block just forward of the head for several seconds before having to remove them. If you can't, check the t-stat. If would be a real good idea to replace both the t-stat and water pump impeller if you have no idea when the last time this was done.<br /><br />The temp sensor is a bimetal gizmo. Temp extremes will cause it to close making up a circuit to the alarm horn mounted in the control box or if the key switch is in the dash, connected to the wire harness under the dash. If you get continuity across the sensor weather cold or hot, the sensor is bad and should be replaced. From your post, it would appear though that the sensor is doing what it should be doing and the engine is over heating. <br /><br />As I have already posted, replace the t-stat and impeller. Should take care of the problem.<br /><br />Keep us posted.

Re: 30hp with temp problem?

There is a process to check your temp sensor. If you have access to a service manual, it will indicate the actual process. For my engine's temp sensor, you put oil in a pot,put the sensor in with a cooking thermometer, and heat the oil slowly over your cooking range. Check at specified temps with an ohmmeter. Each specified temp should have a specified ohmmemter reading. If it is out of the specified range, replace the sensor.<br /><br />I agree with OBJ, just replace the T-stat and impeller to be sure they aren't malfunctioning. I would try the above if it still isn't working.

Re: 30hp with temp problem?

Thanks,<br /><br />but what is the t-stat? Where is it placed? Is it the termostat? I called a local Johnson outboard company to hear if I should try to replace the termostat, impeller and sensor but they didn't want to help (hung up on me!). Guess I'll never call them again...<br /><br />Regards<br />-tsl-

Re: 30hp with temp problem?

T-stat is the thermostat. You really need a manual.<br /><br />Post your model number here and someone will tell you the year of your engine. Manuals can be found at your dealership, ebay, etc.<br /><br /><br />Try this:<br /> http://www.marineengine.com/manuals/seloc/johnson_evinrude.html

Re: 30hp with temp problem?

Thanks,<br />the modelnumber is BJ30ELECS.<br />I have tried finding it on the net but no luck. The closest I've found is BJ30EEE which is a Johnson 30hp from 1990.<br /><br />rgds<br />-tsl-

Re: 30hp with temp problem?

I'd ask this as a new post...asking what's my model year?...giving your serial number.

Re: 30hp with temp problem?

OK, I've found the model year. It's from 1998.<br />I have just purchased a t-stat and an impeller. Now the question is if I can replace them myself. Do you strongly advice using a manual or can someone give me some tips on how to replace these parts?<br /><br />rgds<br />-tsl-

Re: 30hp with temp problem?

Its not hard but you should go to the bottom of this web page and order a manual regardless. Best money (~$30 US) you will ever spend on your boat.

Re: 30hp with temp problem?

Hi again,<br />I have replaced the t-stat and the impeller. Now it runs on both cylinders. But, the engine is not responding like it should on low rpms. At idle it dies but at max speed it goes ok (though it takes a while to get there).<br />There are NGK plugs in but I'm thinking of replacing them with the original Champion QL77JC4. Do you think it would help?<br /><br />Rgds<br />-tsl-