New to this engine. Temperature Questions..

[Landon116]

Hi all.

I got a new to me johnson 70 hp 2001 2 stroke outboard. Just before I picked it up, the p.o rebuilt the power head from bottom to top (with receipts and I know it was done).
After idling in a barrel of cold hose water, the cylinder head temps are concerning me. The top cylinder temp is around 145, Second down is around 165-170 and the bottom third will creep to 190-200. BUT, when I rev it up a little the temps drop immediately to around 165.
Tell tale is full blast
overheat circuit functions and has not alerted
runs great
water will sputter our exhaust holes once revved.
upon removing thermostat ( for diagnoses purp.) All cylinder temps will stay COOL. Like 120..

my plan of action: water pump kit, thermostat kit, and possibly remove the head to check it.

It runs great all the time and looks to stay cool when I'm running it on the boat down the river.

Yall please let me know of normal temperature readings, and what I should do.

Thank you!!

 

[oldboat1]

Based on your description, it sounds offhand like a t.stat issue. There may be other issues to explore, though. This thread may raise more issues than it resolves, but worth looking at (design issues pertaining to water circulation): https://forums.iboats.com/forum/engi...vice-bulletins I don't know if any of it applies to your engine.

At or over 160F is too hot.

[Edit. I would put in a new impeller as well, as per your plan -- river running (sand) is hard on them.]

 

[Landon116]

Based on your description, it sounds offhand like a t.stat issue. There may be other issues to explore, though. This thread may raise more issues than it resolves, but worth looking at (design issues pertaining to water circulation): https://forums.iboats.com/forum/engi...vice-bulletins I don't know if any of it applies to your engine.

At or over 160F is too hot.

[Edit. I would put in a new impeller as well, as per your plan -- river running (sand) is hard on them.]

Thanks oldboat, I reviewed that thread and some of it does apply and im going to follow some the revisions.

Do you happen to know if these engines have any more poppet style valves that open after a certain rev-range?

Again, Thank You for taking the time.

 

[racerone]

The thermostat also is the poppet valve.

 

[Landon116]

The thermostat also is the poppet valve.

Got ya. Thanks. I had problems also getting a pee stream out of the engine when on muffs, but its fine when submerged.. So maybe the pump isn't drawing enough to prime it..

 

[Landon116]

If I ever get this fixed, I will post the solution here for future reference for others. If I dont post it.. well..

 

[racerone]

Pressurized water has more air dissolved in it than lake water.-----Some motors are shy when running on a hose.

 

[F_R]

As I have said so many times, you cannot test a cooling system by running on a hose. The water pump is not pumping when you are doing that---only allowing hose water to pass through. Compare your city water pressure with normal water pump pressure. How could they be expected to have the same flow characteristics?

 

[Sea Rider]

Will need a high water pressure outing hose to muffs and muffs not lossing any water pressure sideways for best overall testing. The only way to know the correct working temp for any outboard is to measure it right out of the box as a temp refference as will have all water paths immaculate clean to perfection and OB cooling at its proper temp range.

If that OB has a temp sensor and is not kicking in when running on water at say 3/4 to full wot rpm range, no need to worry..

Happy Boating

 

[Landon116]

As I have said so many times, you cannot test a cooling system by running on a hose. The water pump is not pumping when you are doing that---only allowing hose water to pass through. Compare your city water pressure with normal water pump pressure. How could they be expected to have the same flow characteristics?

I agree 100%, I have been running it in a barrel to simulate "normal circumstances". I was just pondering if it was a clue to a fault. I had only ran it once on muffs when I got it and I knew the 40 psi water pressure hose wasnt going to give me an idea if the pisser was sprayin on its own or not. Thanks for the comment though!

 

[Landon116]

Will need a high water pressure outing hose to muffs and muffs not lossing any water pressure sideways for best overall testing. The only way to know the correct working temp for any outboard is to measure it right out of the box as a temp refference as will have all water paths immaculate clean to perfection and OB cooling at its proper temp range.

If that OB has a temp sensor and is not kicking in when running on water at say 3/4 to full wot rpm range, no need to worry..

Happy Boating

Okay, thanks Sea Rider. Temps switch has not kicked on and it stays cool at 3/4 to full throttle. Thank you for the info.

 

[Sea Rider]

Okay, thanks Sea Rider. Temps switch has not kicked on and it stays cool at 3/4 to full throttle. Thank you for the info.

You're welcome Landon,

Keeping with the tech conversation. It's a very bad idea to run any engine on a barrel for extended time periods as will inevitably be heating the water with the heated water exiting the prop. In real boating world, cant't possibly cool properly an engine with heated water recirculating constantly inside a barrel. Will need a hose to dump cold water over the barrel and a lower faucet to drain the heated water out as to have a much colder water temp to work with and check whatever you want to check.

A friend of mine seized up a new engine while undergoing its break in period using a barrel, that there are idiots, there are..LOL!!

Check if temp remains same at full throttle say running for at least 30 minutes on flat calm water cond.. Engines having impeller, thermostat, excesive salt buil ups issues will tend to overheat when full throttle is in demand for extended time periods. If all goes well you can sleep in peace..

Happy Boating

 

[F_R]

I hope you are not running a 70hp motor 3/4 to full throttle in a barrel....or muffs

 

[Faztbullet]

The "pisser" has nothing to do with cooling.....Its a water pump indicator to tell ya water pump is working.

 

[Landon116]

The "pisser" has nothing to do with cooling.....Its a water pump indicator to tell ya water pump is working.

Right.. that's why I was referencing it, to indicate pressure is being generated by the water pump, and have been using an infrared temp gun at the cyl head. Thank you for the reply