new engine overheats

[svb165]

This is a 2006 Chris Craft Speedster. I did the engine swap myself.. I went from a 5.0 mpi to a 350 Mag mpi after the 5.0 froze and cracked the block badly..
the swap went well the engine runs well, it seems to be pumping water as i have pulled manifold hoses while its running and it iS circulating. yet it still slowly but steadily goes up and will hit 200.
I put a new water pump kit in the out drive and a thermostat, but thats about it.
Oh and this is new but old,,,,, I did the engine swap in 2016 and am just now getting to breaking it in.
does anyone have any tests or hits as where to look? it has the one knob drain system as well... I wouldn't mind bypassing that thing also..

 

[ESGWheel]

I am not familiar with your set up so a couple of questions and a suggestion

• When gets to 200, are you on muffs or in the water putting around?
• 
  
• Does just breaking it in mean that since 2016 this engine has not been run?
• 
  
• Was the engine ever run and the temps stayed where they should have?

Suggestion: pull the thermostat and see if it still creeps up to 200.

 

[Scott Danforth]

assuming since the outdrive has the pump in it, this is an alpha unit.

did you replace the impeller back in 2016, or yesterday? because rubber parts go off of calendar hours, not use hours. your 9 year old rubber could be deteriorating and you could be loosing vanes.

are you getting 15 psi and about 7 gpm thru your raw water pump to the thermostat housing?

did you back-flush the PS cooler and line back down to the drive?

it has the one knob drain system as well... I wouldn't mind bypassing that thing also..

that is the block-buster system as it only works well when new, prior to all the crud being pumped into the water jacket later on.

 

[ROY WILLIAMS]

engine coolant no water! YES! distilled water 50%-antifreeze coolant 50%.
svb165 DAMAGED OF THE ENGINE! WATER ICE.

 

[ESGWheel]

engine coolant no water! YES! distilled water 50%-antifreeze coolant 50%.
svb165 DAMAGED OF THE ENGINE! WATER ICE.

I am almost afraid to ask, but how is this helpful to the OP’s issue?

 

[nola mike]

I am almost afraid to ask, but how is this helpful to the OP’s issue?

Best to just let it ride and keep moving.

 

[svb165]

I am not familiar with your set up so a couple of questions and a suggestion

• When gets to 200, are you on muffs or in the water putting around?
• 
  
• Does just breaking it in mean that since 2016 this engine has not been run?
• 
  
• Was the engine ever run and the temps stayed where they should have?

Suggestion: pull the thermostat and see if it still creeps up to 200.

it goes up even on a strong hose with double feed muffs. yes it sat for about 8 years not broken in.. never even run so internally it was still covered in break in oil,,,,, least thats what I'm telling myself LoL it runs great, it fired right up after sitting all winter without even a tick. no its only got mayyybe t
2 hours on it so far.

I will pull the thermostat and see what it does.

 

[svb165]

engine coolant no water! YES! distilled water 50%-antifreeze coolant 50%.
svb165 DAMAGED OF THE ENGINE! WATER ICE.

Lake water ,, cold weather,, not drained.. not good

 

[svb165]

assuming since the outdrive has the pump in it, this is an alpha unit.

did you replace the impeller back in 2016, or yesterday? because rubber parts go off of calendar hours, not use hours. your 9 year old rubber could be deteriorating and you could be loosing vanes.

are you getting 15 psi and about 7 gpm thru your raw water pump to the thermostat housing?

did you back-flush the PS cooler and line back down to the drive?


that is the block-buster system as it only works well when new, prior to all the crud being pumped into the water jacket later on.

Yes alpha 1 gen 2 1:62 ratio no I did the impeller last fall so that's fresh but no,,,, I havent back flushed,, the PS cooler?? it did sit in a barn full of mud wasps in Texas with the prop exposed.. it seems to be circulating water ok though. the one knob drain system ads a **** ton of hoses and I'm wondering if that doesn't hinder cooling,,,,, I'm not familiar with it myself. I replaced the manifolds during the repower and the boat only had 80 hrs on so nothings clogged up there.

 

[Scott Danforth]

I will pull the thermostat and see what it does.

Don't do that.

 

[ESGWheel]

Don't do that.

@Scott Danforth
So I do not offer that advice again please help me understand why bad… thanks

 

[Scott Danforth]

@Scott Danforth
So I do not offer that advice again please help me understand why bad… thanks

A thermostat in a marine engine does two things. It is regulating flow and being used as a mix valve to modulate temperature.

It is used to keep full flow to the exhaust and regulate flow to the motor.

Without it, the exhaust doesn't get enough flow and runs too hot, the block and heads get too much flow and will run too cool, causing additional wear.

 

[svb165]

oK yes I understand the thermostat does control flow. I'm trying what I can to determine why its over heating.. Do you have any OTHer suggestions as to why it may be overheating? as I said water SEEMS to be circulating through the system yet it slowly gets hot. it takes about ten minutes and then the temp rises. I'm changing the stat today, as I just found out it was messed with After I had done the engine swap.. smh

 

[Scott Danforth]

Measure raw water flow. Should fill a 5 gallon bucket at 1000 RPM in 16 seconds or less

 

[ESGWheel]

A thermostat in a marine engine does two things. It is regulating flow and being used as a mix valve to modulate temperature.

It is used to keep full flow to the exhaust and regulate flow to the motor.

Without it, the exhaust doesn't get enough flow and runs too hot, the block and heads get too much flow and will run too cool, causing additional wear.

Thanks for the explanation. I now understand that even with the t-stat fully open there is enough ‘blockage’ to cause the needed flow of water to the manifolds.

 

[Scott Danforth]

generally not running a thermostat requires the use of a restrictor disc. basically a washer with about a 1/2" hole in it.

 

[svb165]

Thanks, I put a new one in at rebuild but have now learned it was changed or pulled two years ago when a cousin tried to run it.. smh I will dig into the t stat and do a good back flushing to make sure everythings clear then if need be test the water pump/circulator flow this weekend, its 45 and raining today.

 

[cyclops222]

Cousin had fun with a new engine. YEEEHAWWW

 

[ESGWheel]

I am putting my money on you finding remnants of Texas mud wasps in the t-stat and elsewhere

 

[svb165]

I went ahead and opened up the T-stat housing and found the stat was the one I put in when I re powered in 16. it never was taken out or changed by anyone else after all.. I put a NEW stat in anyway it and I took it to a pond to test rather than wondering if the hose was feeding it enough. it stayed cool for 15 min easy,, it took some time for the t stat to open and it stayed in parameters for a while idling around near the ramp so I motored out in the pond,, still fine I brought it up on plane ,, it stayed right about 165-170 for a bit,, 3/4 - a mile I'd say,,, then started creeping up again. at about 190 I put it in neutral at a high idle and it stopped rising but didn't drop much so I shut it off and went and opened up the motor drain ftfoi and emptied the motor. fired it up and it cooled instantly, another loop around the pond and sure nuf it started getting hot again.
so off comes the outdrive,, maybe the o ring at the gimbal is pinched,, maybe the ring between the two half's is punched/leaking,,,