Re: How to adjust idle 150hp
MaxTurbo - I think you all might have got a little sidetracked with the mention of 93 octane fuel. The idle on carb'd mercs of your era are controlled by a couple of things. Some engines have an advance control module, some have idle control modules and some just rely on the switchbox but all of them rely on some sort of manually set initial timing.
Verify that your initial timing is set to spec and if it is, try adding a small amount of advance to it, maybe just an 1/8 of a turn at a time until you find the sweet spot. Your idle in neutral should never exceed 800 rpm with 700 to 750 being where some older motors seem to like it. The book should be calling for 650 at idle in forward gear but a worn engine may need a little more. The engine should also respond for you with quicker cold starts.
The Merc recommended cold start procedure is a 5 second choke routine, (ie. Turn the key, push the choke, count to 5 using the 1001, 1002 method, release the choke and start the engine with the throttle in the start position, (out of gear and just slightly ahead of idle, your control might be equiped with a cold start lever instead).
Use short cranking bursts when starting. Long cranking will only burn up your starter. If the engine refuses to start after more than a few cranking bursts then stop, wait 30 seconds and try cranking again. If it still won't start, wait a couple of minutes and repeat the starting steps from the begining. Unless there is something far more serioulsy wrong with your engine, I doubt you'll ever repeat if you follow this procedure.
As for the high octane gas. Octane is what is used to slow down the burn rate of fuel. The longer burn rate of high octane fuel causes fuel to remain burning further and more evenly through the stroke which in turn means more power to the shaft. It also means that there will be more unburnt fuel in the exhaust and that means raw fuel polution. Hence, the push towards low octane fuels and additives.
Low octane fuels burn faster and more violently and often cause engines to rattle the wristpins of the pistons and slap piston skirts against the cyliner walls. On a four stroke it slams the valves shut also which is why we now have hardened valve seats. Additives such as Ethanol, MTBE and BioDiesel are supposed to help combat the problem but they have their evil sides also.
Aviation fuel is probably the only gas you can get that is not completely bastardized but I can't see paying that much for fuel.
MaxTurbo - I think you all might have got a little sidetracked with the mention of 93 octane fuel. The idle on carb'd mercs of your era are controlled by a couple of things. Some engines have an advance control module, some have idle control modules and some just rely on the switchbox but all of them rely on some sort of manually set initial timing.
Verify that your initial timing is set to spec and if it is, try adding a small amount of advance to it, maybe just an 1/8 of a turn at a time until you find the sweet spot. Your idle in neutral should never exceed 800 rpm with 700 to 750 being where some older motors seem to like it. The book should be calling for 650 at idle in forward gear but a worn engine may need a little more. The engine should also respond for you with quicker cold starts.
The Merc recommended cold start procedure is a 5 second choke routine, (ie. Turn the key, push the choke, count to 5 using the 1001, 1002 method, release the choke and start the engine with the throttle in the start position, (out of gear and just slightly ahead of idle, your control might be equiped with a cold start lever instead).
Use short cranking bursts when starting. Long cranking will only burn up your starter. If the engine refuses to start after more than a few cranking bursts then stop, wait 30 seconds and try cranking again. If it still won't start, wait a couple of minutes and repeat the starting steps from the begining. Unless there is something far more serioulsy wrong with your engine, I doubt you'll ever repeat if you follow this procedure.
As for the high octane gas. Octane is what is used to slow down the burn rate of fuel. The longer burn rate of high octane fuel causes fuel to remain burning further and more evenly through the stroke which in turn means more power to the shaft. It also means that there will be more unburnt fuel in the exhaust and that means raw fuel polution. Hence, the push towards low octane fuels and additives.
Low octane fuels burn faster and more violently and often cause engines to rattle the wristpins of the pistons and slap piston skirts against the cyliner walls. On a four stroke it slams the valves shut also which is why we now have hardened valve seats. Additives such as Ethanol, MTBE and BioDiesel are supposed to help combat the problem but they have their evil sides also.
Aviation fuel is probably the only gas you can get that is not completely bastardized but I can't see paying that much for fuel.