water temp issue on 1989 70 HP

[bob johnson]

so I finally fixed my temp sender-gauge issue and I notice the temps are not rising at idle on muffs... I touch the head and it is air temp...no heat at all.....I rev the motor to 1500 for 5 minutes....temps don't go up...head is still cold. I pulled the muffs off and after about 30-40 seconds the guage slowly started to move off 120 degree.. and the head is now warming to the touch......so I pulled the thermostat cover to see if they was a t-stat!...there is with a spring....is it possible these things can get stuck OPEN? im guess they can get stuck closed.....but cant imagine they would get stuck open......

bob

 

[jbuote]

Not an expert, but I've seen some on cars get stuck open..

​I'd probably take out the thermostat, make sure it's closed, then put it in a pot of water..
​With a thermometer in the water with the thermostat, start to bring water to boil..
​Watch what temp the thermostat opens.. Then turn heat off and let water cool.. Note temp thermostat closes (or if it does..)
​That should tell you if it's good or not I think...

​And I'm sure you're aware, but you were planning on replacing your impellor now right?
​Running without water will destroy an impellor almost instantly I believe...

​For what it's worth...

 

[racerone]

Does the hose for the telltale come off the top of the block, yes or no ?---Have you looked into the waterpump kit with the thermostat spring / cover change, yes or no ?---Running on a hose is NOT a good way to test cooling system !

 

[Fed]

The sky won't fall with a 30-40 second dry run and you a wet one.
I Posted my thoughts in your other thread Bob, I didn't know you started a new one.

 

[oldboat1]

have to believe the cold water temp at the flusher has something to do with it too -- maybe 40 degrees or so coming out of the hose?

 

[bob johnson]

Does the hose for the telltale come off the top of the block, yes or no ?---Have you looked into the waterpump kit with the thermostat spring / cover change, yes or no ?---Running on a hose is NOT a good way to test cooling system !

the water feed from the motor for the tell tale come off the bottom of the side of the block...(off a large cover)...it is "T" eed to the water pressure hose feed as well...

the "testing" of the cooling system wasn't the main plan and in an afterthought it is preliminary....but after all these years and all my motors , ive never felt a head soo cool idling on muffs...the cool head was just a DISCOVERY of finally getting a temp guage-sender combo working.....

 

[racerone]

There was a service bulletin that came out 23 years ago that recommended moving the tell tale fitting to the top of the block !!-----Today there is a water punp kit with different poppit spring and a replacement cover to address cooling issues with these motors.

 

[bob johnson]

im looking to get a new t-stat, im going to go down to my main parts guy who I have bought motors off before... he has lots of older stuff still on the shelves. but id like to be informed before I go..... this drawing is of the 1989 70 HP..... its looks like the "t-stat assembly is comprised of many parts... 23, 37, 38 and 39....14 and 15 I think are pressed into the head and usually don't get replaced...

but those parts add up to $75..... for a T-stat!!!!!!!!!!!!....I have the large spring and a "body" that I thought was the t-stat...but apparently it comes apart..... maybe I only need the internals..ie 38 and 39? is that right?....

 

[racerone]

Have you looked into moving the telltale hose fitting , yes or no ?----Have you looked into the waterpump kit with the cover / spring replacement , yes or no ?

 

[bob johnson]

actually I have thought about moving the tell tale because disassembled a 1987 70 hp about 5 years ago and cleaned and painted every part and have the block honed slightly and got a new piston and all new rings and a full gasket kit, and was going to move the tell tale on that, but I never assembled the motor!.....but at this point my mind isn't thinking over heat issues.... im having trouble getting the motor to warm up!........ plus I have only ran it on the water for 30 minutes and the temp guage-sender wasn't working then.... so I am doing one thing at a time..... water pressure is about 8 psi at idle and goes to about 20 psi at full throttle.... but to my thinking, I need to address the t stat staying open FIRST...... the motor will be used often in the winter...so I need the t stat to stay closed until the motor warms up!

 

[racerone]

The thermostat lifts off the seat when water pressure increases.-----Running on a hose is NOT a good test of cooling system function.

 

[bob johnson]

so is there a kit for the relocation that has the exact place to drill and tap? the guy I bought the new t stat from says you need to drill in a specific place and he cant remember the dimensions...... he thinks almost all these 70 hp 's go bad from this issue.... so im thinking Ill make all the upgrades I can...... I have the temp guage so Ill be able to monitor the temps . worst comes to worst, I shut the motor off, if they go too high

 

[racerone]

I am working on a 96 model now.----Scored pistons.----I can't believe it had the 3 vane impeller in it still.

 

[bob johnson]

do you know the hole location dimensions for the new water outlet for the tell tale..... to me...it seems like how much of an effect can moving the port where the small amount of water leaves the engine!!! unless its an airpocket creation scenario

 

[racerone]

Well, I believe you can find that information right on this site if you do a search for it.----Or perhaps someone else will refer that to you !

 

[bob johnson]

I found it on another site..... the newer water pump kits have the tell tale reroute kit IN IT!......I guess there were several service bulletins....for various things on those motors.

 

[flyingscott]

Water pump kit you need is #0432955. Make sure you remove the pee-hole end and run just the hose. The relocation is because the #1 cylinder would air lock and only fill half way. When they went to the 6 vane pump from the 3 vane it created enough pressure at idle to push the thermostat off of the seat and the motor had a hard time warming up. To relieve that pressure they put a heavier spring on the thermostat and removed the pee-hole end.

 

[racerone]

Why did it take about 10 days to accept good advice / direction on this easy project !

 

[bob johnson]

for one, I didn't have an OVERHEAT problem, so I wasn't looking to fix an OVERHEAT issue... I had temp gauge and sender issues, I had tach issues , and THEN I had an issue with the motor running too cold.......and sometimes the good advice is very cryptic..... your previous post alluded to the fact you KNEW the issue and said for me to go search for the answers...then when someone answered or I said I found it... you aknowledge you knew the advice..... are you trying to teach me a lesson? it MAY turn out I don't have an overheat issue at all right now......it may turn out that there already is a 6 vane impeller in the LU and it overcomes the locked air pocket.....one step at a time......im learning this motor.......

 

[flyingscott]

for one, I didn't have an OVERHEAT problem, so I wasn't looking to fix an OVERHEAT issue... I had temp gauge and sender issues, I had tach issues , and THEN I had an issue with the motor running too cold.......and sometimes the good advice is very cryptic..... your previous post alluded to the fact you KNEW the issue and said for me to go search for the answers...then when someone answered or I said I found it... you aknowledge you knew the advice..... are you trying to teach me a lesson? it MAY turn out I don't have an overheat issue at all right now......it may turn out that there already is a 6 vane impeller in the LU and it overcomes the locked air pocket.....one step at a time......im learning this motor.......

The 6 vane pump does not overcome the air lock problem. That is why the pee-hole outlet needs to move.