HELP!!!!! 1988 Johnson 70hp

[seebass322]

Ok, I'm stumped here. Last spring I replaced the water pump, fuel pump, and tons of other items on my 1988 Johnson 70hp 3 cyl. Compression is all set. Just thought I would check the thermostat at the same time, and whamo, the previous owner had removed it!!! Ok, so I put a new factory thermostat and seal back in. Now, the motor runs for sometimes 20 minutes to 2 hours and then the overtemp alarm sounds off. I don't get this alarm with the thermostat out and the water is pumping great preasure. Is there a way of hooking a temp gauge up to the motor, as it does not have one?<br />Any ideas as to what might be the culprit?<br />Help!!!!!!!!<br /><br />Mike~

 

[Walker]

Re: HELP!!!!! 1988 Johnson 70hp

Any history on the motor? Saltwater motor? <br />When does the alarm go off, at cruising speed or trolling speed?

 

[Ranger01]

Re: HELP!!!!! 1988 Johnson 70hp

Another member that may have some knowledge in hooking up an temp gauge is Droll. I belive he did it to ha johnson of his. You can find a link to his rebuild under any post of his, it may say how he did it in there. But i would want to know why the alarm is going of before i did anything to get around it. Sounds like Walker may be on to somthing so answer is questions and see where he can take you.

 

[DHPMARINE]

Re: HELP!!!!! 1988 Johnson 70hp

Maybe someone can find the Service Bulletin about temp sending units being too sensitive on the 3 cylinder motors back then.Not sure if 1988 was included.I believe 1987 was.<br /><br />DHP

 

[OBJ]

Re: HELP!!!!! 1988 Johnson 70hp

Welcome to iboats Mike!<br /><br />Mike...I would ask if the engine is really overheating when the alarm comes in. Would be real apparent if you take the hood off during the alarm. You might also take the t-stat cover back off and see if there is any trash laying about the cavity.

 

[seebass322]

Re: HELP!!!!! 1988 Johnson 70hp

Ah Yes, forgot a few things...Yes, it is a saltwater motor and always has been, though flushed after every weeks worth of use...It doesn't appear to be overheating. The water coming out of the exhaust feels just warm, not torch hot like past motors of mine. Motor speed doesn't matter. I could be at idle or top speed. DHP marine, are you sure about the too sensative thing? That sounds like my problem!!!

 

[OBJ]

Re: HELP!!!!! 1988 Johnson 70hp

The Bulletin says the problem is: (OSB 2221)<br /><br />Warning horn signals overheat condition, motor operates in SLOW warning system during operation of motor where the water temp exceeds 70*F.<br /><br />Old Temp Sw. has a 5 1/2" Tan lead.<br />New Sw. has a 7 1/2" Tan w/blue stripe lead.<br /><br />Just remembered another bulletin about changing the location of the tell tale connection on the exhaust housing. The old position is at the bottom of the cover. The new position is on top. Is yours still at the bottom seebass?

 

[seebass322]

Re: HELP!!!!! 1988 Johnson 70hp

The tell tale drain is on the aft, upper, stbd. side angled about 45deg. from horizontal and 45deg. from centerline on the highest section of cowl, just below where the cover sits. Do you happen to know where the temp switch is located OBJ? If I remember correctly, I think there is a solid brown wire coming out of the upper aft end of the block, near the thermostat housing. I don't have a temp gauge, as you know, but I think that 70deg. sounds right. It just doesn't happen every time the motor is over 70deg., but every trip out with it anyways!! Thank you all for being so helpful!!!!

 

[OBJ]

Re: HELP!!!!! 1988 Johnson 70hp

Follow the telltale hose back to the exhaust cover. Does it come off near the bottom of the exhaust cover or the top?<br /><br />The 70*F water the Bulletin is refering to is the water the boat is setting in not the water coming out of the engine. Sounds like you found the sensor lead.<br /><br />Seebass....there is a flat area on top of the block just forward of the head. When the alarm comes in, put your fingers here. If it's not overheating, you will know.<br /><br />I think the problem is either the alarm horn module is going bad or the temp sensor is going bad or you need to relocate the tell tale supply hose at the exhaust cover to the top of the exhaust cover....reason being is that the block may be getting air bound and not filling with water. Relocating the tell tale supply to the top of the exhaust cover, let's the block vent off and fill up with water. It's a good idea to do no matter if it's the current problem or not.

 

[seebass322]

Re: HELP!!!!! 1988 Johnson 70hp

In reference to the water temp. I usually am running the outboard in 55-73deg water, though with the alarm, it doesn't matter. Moving the tell tale is a great idea, but does that mean that I need to drill and tap that cover, or are there provisions for it already>? The flat area that you are referring to is the area that the manual says to rub a wax temp stick on to verify engine temp. Thanks Again!!!<br />Mike

 

[OBJ]

Re: HELP!!!!! 1988 Johnson 70hp

Mike....drop me an email and I'll send you the bulliten which will show you where to drill and tap.<br /><br />outboardjim@comcast.net