1969 85hp Johnson overheat problem

[thornbg]

I changed the impellor a month ago, first time for me, useing the manual and paying attention to how it was already put together. I'm pretty confident in the job I did with the exception of aligning the pickup tubes. I got it out on the water last weekend. I ran pretty wide open for about 45 minutes or so and then the overheat light came on. I have since tore apart the thermostate housing and that seamed to be in good working order. Anyhow how do I tell if it's pumping water correctly. All I have ever seen before and after I changed the impellor is some light spray out of the exhaust ports. Also if I did miss align the pickup tubes when I put the lower end on, does anyone have any tips on how to get them in place correctly? They only slide into the pump housing about 3/8" and with that little overlap you can't see inside anymore to know.

 

[o/b tech]

Re: 1969 85hp Johnson overheat problem

If the motor ran for 45 minutes, than you should have the pick-up aligned in the water pump. If the old w/p had pieces break off from the impeller, they can become lodged inside the pick-up tubes and or the powerhead. Aldo look down in the cavity below the water pump, where the water intake screens are on the gearcase. This may also be plugged.<br /><br />With the engine running, try touching the flat exhaust cover that is between the two heads. Be careful of moving parts.If the cooling system is working properly, the cover will not be too hot to touch.

 

[thornbg]

Re: 1969 85hp Johnson overheat problem

Screens were clear and the old impellor was intact. There's a wiring plate infront of that exhaust plate. It's mounted there with some thick rubber washers between. I beleive I can fit my fingers down in between a little ways. Anyhow if it's not to hot then is it possible the temp sensor is bad.

 

[thornbg]

Re: 1969 85hp Johnson overheat problem

Anyone have anymore comments on this?

 

[ledgefinder]

Re: 1969 85hp Johnson overheat problem

Right, the ignition's over the exhaust plate on the 1969-72 V4s, so just rest your fingers on either of the cylinder banks. When the motor's warmed up, it should be hot enough that you can rest your fingers on the cylinder banks for around 2 or 3 seconds. I think the thermostat setting is 140 F, but not sure I'm remembering right. It feels hot to me (not warm) but not enough to burn the fingers.<br /><br />There is no telltale on those motors. The 'mist' you describe is correct, and it should be a heavy rain under high throttle, when warmed up.<br /><br />There a plastic guide tubes that fit over the two pickup tubes, did you find & use those? If what I'm saying about the guide tubes, post back & let us know.<br /><br />Pull the hose from one of the cylinder banks leading to the thermostat box. With the engine in the water (not on a hose), start it up. If you get a good flow out of that hose, the pump is pumping. That will also 'short-circuit' your thermostat, so if it cools OK with the hose off, but overheats with the both hoses on, your thermostat or venostat is not opening. Sounds like it is though, if you're getting mist from the exhaust relief ports.

 

[Solittle]

Re: 1969 85hp Johnson overheat problem

I don't know the 69 but is the cover for the thermostat readily available? If so you could remove the cover and t-stat and start it up & see what kind of flow you get. Many of the V4s have rubber deflectors in the water passages (don't know about yours - check you manual). You have to pull the heads to check. Over time the rubber gives out and can block the water flow.

 

[thornbg]

Re: 1969 85hp Johnson overheat problem

Ledgefinder<br />Yes I did use the guide tubes, I placed the guide tubes into the colars of the pump housing and then re-attached the lower end to the exhaust tube. There's really not a good field of vision when attaching the lower end to see to align the guide tubes onto the picup tubes. I did have to make about three stabs at it before I got it right. I will follow your suggestion, on Saturday, about pulling one of the hoses off of a cylinder bank and see if the pump is working. I'll get back to you then.<br /><br />SoLittle, the thermostate is somewhat accessible, but not enough to get the back to screw out of the cover, not without pulling pulling off that ignition plate or pulling out the whole thermostate, which by the way I did pull out the thermostate and took it apart. There was nothing stuck or broken inside.

 

[thornbg]

Re: 1969 85hp Johnson overheat problem

Okay last weekend I did take loose the rubber tubes, there was water flow but it was a pretty light flow of water. Anyhow today I decided to drop the lower end and double check to make sure the tubes were aligned right. I found a small chunk of rubber at the very opening of the tube. This is not from the impellor I replaced or the new one, so it's probably a piece that's been in there a while. Anyhow how do clear these tubes out to make sure there are no other pieces?<br />Also how long should those guide tubes be? It seems to me that they those should work is for them to be started over the water tubes and then extend down to where I can see them to align them on to the two ports on the pump housing. The way it is now there only about 2 1/2" and atleast another 1 inch longer would help a bunch.

 

[thornbg]

Re: 1969 85hp Johnson overheat problem

I put the lower end back on, I made sure that I got the tubes aligned with the guide tubes in the collars of the pump housing. It still overheats and I still don't know if there any old impellor parts plugging the water path anywhere.

 

[thornbg]

Re: 1969 85hp Johnson overheat problem

It seems like I'm talking to myself here,<br />anyhow I dropped the lower end again and took the pump housing apart and the impellor back out. I can't find anything wrong with my installation, everything is as according to the Solec book I have. So either the thermostate is the problem or there is blockage somewhere.

 

[REELSPORT]

Re: 1969 85hp Johnson overheat problem

Gary you are right about there not being much room to get the pick up tubes in correctly it happened to me but I knew it in about 2 minutes because thats how long it took to over heat. Try running without thermostat and see if that helps. Sounds like every thing else you have done is correct.

 

[riverkid]

Re: 1969 85hp Johnson overheat problem

If you get a long screwdriver and go behind the ignition plate you should be able to pull the thermostat cover off.(Watch out for the springs!)Check the gaskets and take the little plastic dome shaped piece and file or grind a 1/8" notch in the edge of it.(The dome shaped piece should be on top of your Vernatherm,same as a thermostat.) This allows water to flow up into the cylinder banks at all times.I have a '70 V4 that overheated like yours at lower rpms.this little fix cured it.Keep us posted,C.C.(If you pulled the lower unit off again,take a garden hose and stick it up the water tubes,that should flush them out)

 

[thornbg]

Re: 1969 85hp Johnson overheat problem

Reelsport, I'm getting much better at aligning the tubes now anyway as this is third time I've done it.<br />Before I read reverkid reply I did attach the garden hose, to both tubes, to either side of the thermostate and to each head. I never saw any blockage come out but after I got it back together I ran it at the lake for about 1 1/2 hrs and "no overheat light".<br />Ran real good too for that time then stalled and I couldn't get it started again. I still need to go through the carbs and distributor I'm sure I can get it running better.<br />Thanks for all the help.