7.4GL engine

[Rushan]

Re: 7.4GL engine

No it's not 900 to 1000, it sounds like 400 to 500 rpm.

So should I tune it into gear or just idle it?

For those engines what's the normal idle and what's the idle rpm into gear?

 

[Don S]

Re: 7.4GL engine

You want around 650 to 700 in neutral, using the idle speed adjustment. You may have to use the idle mixture screws to get best mixture, but you still have to use the idle speed adjustment to set the speed.

What's the full model number of your engine, 7.4GL is only the first part, need all the letters after that.

 

[Rushan]

Re: 7.4GL engine

You want around 650 to 700 in neutral, using the idle speed adjustment. You may have to use the idle mixture screws to get best mixture, but you still have to use the idle speed adjustment to set the speed.

What's the full model number of your engine, 7.4GL is only the first part, need all the letters after that.

Thank you for the info. I will try it over the weekend and update you,

The model is 7.4 GL PMDM with GM intank and 4bbl holley carb but the engine lower cylinder block itself I replaced it once with same shape same size mercruiser lower cylinder block

 

[Don S]

Re: 7.4GL engine

Idle rpm is 550 to 650 rpm on that engine. 94 MD model.

 

[Rushan]

Re: 7.4GL engine

Idle rpm is 550 to 650 rpm on that engine. 94 MD model.

Seems my old RPM guage seems not accurate, I got new guage, and now it seems to read better,

I have 1 more question on the guage, it has a setting on the back showing 4poles 8 cylinder, 6 poles , 5 poles, if I use the 4 pole 8 cylinder it reads around 900 on the 5 poles and 6 poles it reads 550 - 600,

So which setting I should use for my engine from the above?

 

[skydiveD30571]

Re: 7.4GL engine

Its an 8 cylinder engine so you set the tach gauge to 8 cylinder.

 

[Rushan]

Re: 7.4GL engine

Its an 8 cylinder engine so you set the tach gauge to 8 cylinder.

Yes sure the 8 cylinder that why I didn't mention the 4 and 6 cylinder in my post,

my question that the 8 cylinder with poles seems to read about 200 more than the setting which mention 5poles or 6 poles without cylinder and I feel that reading more accurate than the 8c with poles, so I wanted to make sure that the poles without the cylinder number is right to be used or should use the 8c with poles and adjust my engine idle based on it and lower it the 200 ?

 

[Don S]

Re: 7.4GL engine

Are you sure you have an IO tach? Sounds like an outboard tach. They count poles on the stator.
Without knowing what tach you have, no one can say how to set it. Whatever you set it to, you need to verify the engine rpm with a known accurate shop tach to make sure your new tach is adjusted right.

 

[Rushan]

Re: 7.4GL engine

Are you sure you have an IO tach? Sounds like an outboard tach. They count poles on the stator.
Without knowing what tach you have, no one can say how to set it. Whatever you set it to, you need to verify the engine rpm with a known accurate shop tach to make sure your new tach is adjusted right.

It's mercury tach and it mention it's for stern drive and inboard also,

the box It mention mercury 6000 rpm tach, for most electric start outboards,stern drives and inboards. Designed for 4-, 6-, 8-cylinder standard ignition or outboards equipped with a 12-pole alternator. Part number 79-895283A03 product of mercury marine.


I hope this can help on the tach I got.

 

[Don S]

Re: 7.4GL engine

The instructions that come with the tach should tell you which setting it should be on.