Re: 5.0 Mercruiser sick
Me............... again
Apologies for the long post but there is a fair bit of data that someone may recognise.
progress to date, enging still running great
But likely wont be for long because we still have that differential temperature problem that appears to NOT be related to the manifolds or risers or seawater pump
Replacing the 160 stat with a 140 has helped a little in bringing the overall temperarure down a little ( salt boat, raw cooled), but Im still chicken to run the boat on cruise for more than a couple of minutes.
Tried a new thermo housing as well , seawater pump pressure is PLENTY........., no vacuum bubles wth clear hose either.
The temperature difference occurs at idle, at 2000 rpm and obviously at cruise and WOT, and the difference increases with the more power the engine makes.
The Temps at the Manifolds outlet coming off the stat housing are 20 degrees different to start with..............
Dumb question but with nothing elses really left to isolate............at hot idle with the thermo wide open the seawater pump hose is quite firm, obviously from the water pressue.
The Large Recirc pump hose isnt though...............yes its a larger hose and so flows more volume with less pressure, but still the water pressure on this seems MUCH less.
Looking at the service manuals, once the stat opens, water from the block flows to the manifold hoses coming from the stat housing, AND to to the circ pump.
Knowing that its not the risers,manifolds, stat, stat housing, seawater pump, could the recirc pump be dodgy.
The boat mechanic says unlikley, and Id agree, it either works or it dont, its not like the steel vane impellor ? But I have learnt with things mechanical, logic sometimes does not apply.
I have seen boat mechanical reports when we were looking to buy in the past and some stated ............inoperative ? recirc pump
What else could cause the exit temps from the stat housing to be 20 degrees different or is this normal ?
Test temps with the state hoses as normal
Temperatures at 1500 hot fast idle
Just below thermostat, 140 as youd expect
Top of stat housing 95
Left bank
Left bank exit from stat 97
Bottom of manifold 100
top 105 ( front and rear)
middle of riser 105
top of riser 121
Right bank
right bank exit from stat 82
Bottom of manifold 78
top of manifold 82 ( front and rear)
middle of riser 82
top of riser 85
SIZE="5"]Test temps with the state hoses reversed [/SIZE]
Temperatures at 1500 hot fast idle
Just below thermostat, 140
Top of stat housing 95
Left bank
Left bank exit from stat 80
Bottom of manifold 80
middle of riser 93
top of manifold 107
Right bank
right bank exit from stat 95
Bottom of manifold 102
top of manifold 105 ( front and rear)
middle of riser 193
top of riser 105
On plane temps at aroun d 3800 rpm 70 % throttle
left bank 160, right 110, this reverses when the stat hoses are changed over, thats why I tend to exlude the mani/risers being at fault
Over to the specialists please.............im stumped
ta
rolf
PS as a separate issue the left manifold riser seems to have a lot of temp gradation from top to bottom......................both man and riser have been pulled and checked, might try the other gasket type, the non restrictor one
.................on there when I got the tub, shiny and new, even off the motor, inside and out .............but maybe ............