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1987 Baja with 7.4 L Engine cuts out

T

Tom J.

New member
Hello, I am new to the Forum and looking for some wisdom on my problem. I have a 1987 Baja Force 320 with twin 7.4L 454 Mercruiser engines. Recently the starboard engine cut out at about 45 mph. I did get back to the Marina limping on just the port engine. However I was able to re-start the starboard engine for a while and get the boat docked. This past weekend I changed both water separator filters and replaced the ignition coil on the starboard engine. But, I'm having the same issue with the engine cutting out after 2 or three minutes. Additionally, when the ignition key is turned on the engine does not always turn over - this is intermittent. Previously, I replaced the slave solenoid on both engines when the ignition key was turned but no engine start at all. Again the engine will eventually turn over and start but still cuts out. My next guess is that it could be the TB-IV ignition amplifier module? But would a TB-IV ignition amplifier module fail intermittently and cause the engine to stall out? Or perhaps this is carburetor problem or bad ground or some other wiring issue? [h=1][/h]
 
First of all, you need to properly define "engine turns over". To motorheads that means, when hit hit the key, the starter engages and the crankshaft rotates. To non-motorheads that can mean it didn't start up and run--big difference! So which is it in your case?

I suspect a fuel starvation issue, possibly caused by a plugged anti-siphon valve at the fuel tank. I'd get that changed out first.

Jeff
 
Hi Jeff, yes "engine turns over" means, when the key is hit (twisted), the starter engages and the crankshaft rotates. Now if this is a a fuel starvation issue, wouldn't BOTH engines stall? OR... are their separate anti-siphon valves at the fuel tank for each port & starboard engines?
 
Each independent supply line should have the anti-syphon valve (if the design requires it - majority do)...

It could also be an intermittent connection....the harnesses and connectors are only three + decades old....this is suggested by the lack of starter engagement when the key is turned to START....I'd suggest a bit more troubleshooting vs random parts changes...
 
I am leaning towards the problem being a an intermittent connection or bad ground. As I originally stated "engine turns over" when the key is hit (twisted), the starter engages and the crankshaft rotates.... But this happens intermittently. At other times, I get nothing when the key is turned - the starter motor doesn't engage and turn over the engine. Anyone have more thoughts?
 
the key switch is intermittent....you won't know until it happens again and you can get some multimeter measurements...the coil gets +12VDC from the key....no if there is ZERO VDC on the coil (key in RUN) then its between the switch and the coil...
 
makomark said:
the key switch is intermittent....you won't know until it happens again and you can get some multimeter measurements...the coil gets +12VDC from the key....no if there is ZERO VDC on the coil (key in RUN) then its between the switch and the coil...
Click to expand...
I'll check it out.... Thanks!
 
Update: Went through all of the electrical connections starting at the ignition key down to the battery and engine. Used a wire brush, steel wool, and sand paper to get all connecting surfaces clean & shiny. Then tightened all connections and sealed it with marine electrical varnish. She started up and ran fine! Kept the engine running with muffs for about 10 minutes, no problems. Then turned the engine off and on several times to verify no intermittent starting issues with the ignition switch. I’ll take the boat out on a test cruise soon, but it seems my electrical continuity problems were solved with some elbow grease…. Appreciate everyone’s input. Thanks!
 
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