OverHeat
05-25-2019, 12:50 PM
#1
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Thread Starter
OverHeat
Here we go again. 496, noticed risers 20* hotter than other engine. Both finally run fine. Next event, new sand bar, using only that engine, got in pretty good, major effort to get out. Some sand in skimmer, after cleared sand bar, engine runs hot, but first water pressure goes Max. Shut it down, limp home on other engine. Replaced an intact impeller, reinstalled. Idle out of canal 15 minutes, then accelerated. Temp creeped back to 185 and pressure maxed again. Could it be heat exchanger clogged or what BUP says circ pump failure/replacement time, or just down stream clog???
05-25-2019, 01:27 PM
#2
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Silt and sand can accumulate anywhere in the system including blockage in your pickup...seen a tow boat (Merc power/thru-hull pickup) that accumulated a blockage on one side of one manifold immediately under riser cutting down the flow - they cleaned out the manifold and temp gun indicated normal temps over the entire engine.
Turns out the owners run the boat very shallow to get to cottage dock stirring up everything from the lake bottom. Heard a year later. the owners had an issue with one side of the engine froze up pushing plugs - under inspection one side of the block had a trickle of water for flow but the cavity was full of wet silt/antifreeze/water... tech assumed it drained when nothing came out. Damage should have taken the block out - not just a plug
Turns out the owners run the boat very shallow to get to cottage dock stirring up everything from the lake bottom. Heard a year later. the owners had an issue with one side of the engine froze up pushing plugs - under inspection one side of the block had a trickle of water for flow but the cavity was full of wet silt/antifreeze/water... tech assumed it drained when nothing came out. Damage should have taken the block out - not just a plug
Last edited by speicher lane; 05-25-2019 at 01:31 PM.
05-27-2019, 10:06 AM
#3
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Thread Starter
I have strainers and the one screened out some shell and sand. Back washing all hoses, no obstructions. Thinking I need to barnacle bust the heat exchanger and replace thermostat which could be stuck mid point, 2004 motor could be original. Looks like original straps on heat exchanger.
06-17-2019, 12:42 PM
#5
Gold Member
Gold Member
I did the acid cleanse last weekend. 30% muriatic 70% water. I made t-fitting and bought a large water transfer pump. Pump in thru the T to the two 3/4 hoses on the risers down thru the manifolds thru the system and out thru the 1.5 at the seawater pump so the water is going backwards. Pump into a 5 gallon pail and recirculate for 30 minutes. Then switch to the hose for another 5 minutes. There was so much crap that settled in the bucket that it was amazing. Shells, small bits of rubber, plastic, stones, some kind of black residue crap. Took the caps off the closed cooling log and it looked phenomenal. I feel like I went to the spa and got an enema.
Seems like lots of 496 owners have been on the board complaining of the same problem lately. I think its just time to flush out the calcium and crap.
Seems like lots of 496 owners have been on the board complaining of the same problem lately. I think its just time to flush out the calcium and crap.
Last edited by Keith Atlanta; 06-17-2019 at 12:44 PM.
