I have a 1989 OMC Cobra 4.3 that is overheating at idle. At planing speed, temperature regulates fine (cycles around 160 degrees). I replaced the impeller (twice, using the rebuild kit the second time - has the housing, plates, etc). In the lake at idle, there is no water coming into the engine compartment (disconnected and checked at the thermostat housing, and checked again before the power steering cooler). If I increase the rpms to about 2000, I get a moderate flow. If I hook up to the muffs with the engine off, and remove the impeller housing, I get a flow about the same as pouring a glass of water out of a pitcher (at the intake to the impeller). That seems low to me, but I have no frame of reference.
The out drive is off now, and I made some 'plugs' and pressure tested both sides of the water path. The path from the impeller to the engine holds pressure pretty well (small leak under the OMC Cobra sticker at a casting access plug). On the path from the lake to the impeller, the air goes into the exhaust path. In other words, the exhaust path and the water intake path are not separated. Does anyone know if this is normal or bad? (Seems bad to me, but I want to ask before I have the lower unit torn apart). Here are a few other things I changed as I was working on this problem: thermostat and both belts.
I have the service manual, but does anyone have a water path or exhaust path diagram? Anyone have a cutaway drawing of the lower gearcase?
I'm really stumped. Anyone have any ideas, suggestions, recommendations on what to try next?
The out drive is off now, and I made some 'plugs' and pressure tested both sides of the water path. The path from the impeller to the engine holds pressure pretty well (small leak under the OMC Cobra sticker at a casting access plug). On the path from the lake to the impeller, the air goes into the exhaust path. In other words, the exhaust path and the water intake path are not separated. Does anyone know if this is normal or bad? (Seems bad to me, but I want to ask before I have the lower unit torn apart). Here are a few other things I changed as I was working on this problem: thermostat and both belts.
I have the service manual, but does anyone have a water path or exhaust path diagram? Anyone have a cutaway drawing of the lower gearcase?
I'm really stumped. Anyone have any ideas, suggestions, recommendations on what to try next?
