Slow starts

[SurfOnH20]

I have a stock Black Max 225 o/b. When I bring it down to an idle the engine tends to load up after a minute or so. When I open it up it runs sluggish for about 2-3 seconds before rpms start to rise. The plugs look great and I am running QuickSilver oil. Since this enigine is EFI, Is there some way to adjust fuel flow, etc to prevent the engine from loading up during idle. The engine runs strong at WOT. Any thoughts or suggestions would be great.

[SurfOnH20]

anyone..?

[Towndrunk]

I'll take a stab at it. Yes, the fuel curve is too rich and it can be adjusted most of the time but I don't know how. Ask for Greg Moss or you tee's help. I'm really a carb man.

[SurfOnH20]

Thanks Towndrunk !! Ill look em up....

[XSive]

Sounds like it probably needs the TPS adjusted...

[Tom Brown]

I'd make sure all the bleed lines are clear also.

[DUCKY]

You have a "black max" 225 and it's EFI? Mercury stopped calling their motors black max in about 1990-91 and I can't think of an EFI 225 HP motor until the 1994 3liter 225 efi, I am confused... Is it a Pro-Max 225?
Either way, if it is EFI, it seems you could have a TPS problem, and or an idle timing issue. You could also have a bad head temp sensor, causing the motor to believe that it's cold. Checking the idle timing is easy, so check it first. If the motor is a 2.4 or 2.5liter, it should be 0-9degrees ATDC at idle. Then check the head sensor. On one of your cylinder heads there will be a sensor with a tan wire, and tan/blue stripe, and a black wire. If memory serves me, the tan/blue interfaces with the ECU and supplies signal to a temp gauge at the dash if the boat is so equipped. Connect a DVM between that wire and a ground so as to read resistance. The number should be fairly high with the motor cold and the resistance should drop as the motor is warmed up. If the value does not change, you have found a problem.

[Towndrunk]

You have a "black max" 225 and it's EFI? Mercury stopped calling their motors black max in about 1990-91 and I can't think of an EFI 225 HP motor until the 1994 3liter 225 efi, I am confused... Is it a Pro-Max 225?
Either way, if it is EFI, it seems you could have a TPS problem, and or an idle timing issue. You could also have a bad head temp sensor, causing the motor to believe that it's cold. Checking the idle timing is easy, so check it first. If the motor is a 2.4 or 2.5liter, it should be 0-9degrees ATDC at idle. Then check the head sensor. On one of your cylinder heads there will be a sensor with a tan wire, and tan/blue stripe, and a black wire. If memory serves me, the tan/blue interfaces with the ECU and supplies signal to a temp gauge at the dash if the boat is so equipped. Connect a DVM between that wire and a ground so as to read resistance. The number should be fairly high with the motor cold and the resistance should drop as the motor is warmed up. If the value does not change, you have found a problem.
I don't think the head sensor plays a part in this. I don't have them on mine and it runs just fine. The idle timing will do it tho.

[DUCKY]

On the laser style EFI, from the factory, the sensor on the right head will have the three wires, and the ECU will adjust injector pulse width up to 10% either way based on the info it receives from that sensor. How else do you think an EFI motor starts and idles on it's own when cold? When I am working on one for myself or a friend, I usually get rid of that sensor, and replace it with a buzzer only sensor, then re-adjust the TPS to compensate. Makes cold starts a little tougher, but it's makes the motor easier to tune later.