REV6String
Cadet
- Joined
- Jul 17, 2018
- Messages
- 17
Looking for some help on my 1989 Cobia with a mercruiser 5.0L, Alpha 1 outdrive, rochester 4bbl carb.
I overheated my boat about 5-6 weeks ago when I lost my raw seawater pump. The engine temp didn't go over 185 when I limped it back into the marina, but my first clue to the overheating was the exhaust boots off the exhaust risers both popping and smoking. I've replaced all the rubber on both sides of the exhaust, cleaned the risers, verified the manifolds were clear, replaced the water pump in the lower unit, and tested pump output and water flow thru the engine both independently and also assembled.I inspected the exhaust system for damage or obstructions and found none, shutters were intact.
Since this boat sat for about 5 years before I got it, I've gone thru the ignition system and replaced all components: plugs, rotor, pickup in dist. I checked the fuel strainer at the carb, adjusted the choke and it ran really well before the overheating with no performance issues, it would get up to 35 mph at 4000 rpm with 5 people onboard.
Tonight I put it in the water and the cooling system is working great, but now there is very little acceleration above 1600 rpm. The engine rpm changes but the boat doesn't go any faster and runs worse as the throttle and RPM's increase. Can an ignition module fail partially like this? It got hot enough in the engine compartment to warp the air filter cover, so it would seem likely an electronic component might fail under those circumstances but I looked at the graph for advance and it seems that I would have issues well before 1600 rpm.
While working on the exhaust I changed the oil and filer, and a very worn sticky shift cable (installed per Merc service manual).
Blown head gasket? No water in exhaust or oil, no oil in discharge. Any help?
I overheated my boat about 5-6 weeks ago when I lost my raw seawater pump. The engine temp didn't go over 185 when I limped it back into the marina, but my first clue to the overheating was the exhaust boots off the exhaust risers both popping and smoking. I've replaced all the rubber on both sides of the exhaust, cleaned the risers, verified the manifolds were clear, replaced the water pump in the lower unit, and tested pump output and water flow thru the engine both independently and also assembled.I inspected the exhaust system for damage or obstructions and found none, shutters were intact.
Since this boat sat for about 5 years before I got it, I've gone thru the ignition system and replaced all components: plugs, rotor, pickup in dist. I checked the fuel strainer at the carb, adjusted the choke and it ran really well before the overheating with no performance issues, it would get up to 35 mph at 4000 rpm with 5 people onboard.
Tonight I put it in the water and the cooling system is working great, but now there is very little acceleration above 1600 rpm. The engine rpm changes but the boat doesn't go any faster and runs worse as the throttle and RPM's increase. Can an ignition module fail partially like this? It got hot enough in the engine compartment to warp the air filter cover, so it would seem likely an electronic component might fail under those circumstances but I looked at the graph for advance and it seems that I would have issues well before 1600 rpm.
While working on the exhaust I changed the oil and filer, and a very worn sticky shift cable (installed per Merc service manual).
Blown head gasket? No water in exhaust or oil, no oil in discharge. Any help?
