Slimmdaddy
Cadet
- Joined
- Apr 2, 2011
- Messages
- 22
I have a 1974 150 that is causing me some sleepless nights. I just swapped this 150 onto my boat replacing a perfectly good and dependable 115 because I want more power (yea I have heard all the grief about taking off the 115 that was running as perfect as when it was new but I wanted more power for some reason that eludes even me at this point). When you start this 150 on the hose it starts as easy as a new engine, idles super smooth and is peppy when the throttle is worked. In the lake, it starts equally as well and idles about 600 rpm in gear very smooth.
The aggravation occurs when trying to throttle up, it will not rev past approximately 1300-1400 rpm and just 'bogs' down as if it is out of gas. If I choke it when it bogs down the engine just dies. It will start right back up faster than you can let pressure off the key.
Things to know:
Boat - 1978 Cobra Phantom 17' (looks exactly like this Bullet --> 1986 19' Bullet Bass Boat)
Prop - Quicksilver 21 pitch (had same prop on 78 115 and it launched like a missile and top out at 49.5 mph gps)
Compression - 130-135 on all cylinders (checked warm, checked by two different people using two methods, results are within 3psi each cylinder between the two methods)
Timing - 5 degrees BTDC at idle, 21 degrees total timing
NEW - fuel tank, all fuel lines, fresh rebuilt carbs (have tried 2 sets both rebuilt WMK-19 with economizer ports blocked off per Mercury's $20 classic outboard service call)
Something I noticed is that the distributor appears to have lots of grease oozing from the separation points and when I remove the cap there is grease and oily film inside the cap and under the disc that spins above the rotor button. The rotor button appears to be fine, no cracks or chunks missing. The distributor cap contacts show minimal signs of wear but are not corroded. If a screwdriver is used to jump spark from the tip of the spark plug to ground while the engine is running, all cylinders show the same drop in power.
Can the ignition be dropping out under load? Could stuck reed valves cause this problem?
My mind is going in a million directions it seems so I will proof read this a time or two and post...then add additional info as requested.
Thank you for any help, it will be greatly appreciated.
The aggravation occurs when trying to throttle up, it will not rev past approximately 1300-1400 rpm and just 'bogs' down as if it is out of gas. If I choke it when it bogs down the engine just dies. It will start right back up faster than you can let pressure off the key.
Things to know:
Boat - 1978 Cobra Phantom 17' (looks exactly like this Bullet --> 1986 19' Bullet Bass Boat)
Prop - Quicksilver 21 pitch (had same prop on 78 115 and it launched like a missile and top out at 49.5 mph gps)
Compression - 130-135 on all cylinders (checked warm, checked by two different people using two methods, results are within 3psi each cylinder between the two methods)
Timing - 5 degrees BTDC at idle, 21 degrees total timing
NEW - fuel tank, all fuel lines, fresh rebuilt carbs (have tried 2 sets both rebuilt WMK-19 with economizer ports blocked off per Mercury's $20 classic outboard service call)
Something I noticed is that the distributor appears to have lots of grease oozing from the separation points and when I remove the cap there is grease and oily film inside the cap and under the disc that spins above the rotor button. The rotor button appears to be fine, no cracks or chunks missing. The distributor cap contacts show minimal signs of wear but are not corroded. If a screwdriver is used to jump spark from the tip of the spark plug to ground while the engine is running, all cylinders show the same drop in power.
Can the ignition be dropping out under load? Could stuck reed valves cause this problem?
My mind is going in a million directions it seems so I will proof read this a time or two and post...then add additional info as requested.
Thank you for any help, it will be greatly appreciated.
