Another how to timing question

[nateo]

So took the boot to pro shop this week and still didn't get it fixed. When I set the timing should I be able to set the base timing regardless of where the idle screw is at or do I need to start with it at the lowest setting? Assuming it needs to be at lowest setting but i'm getting tired of taking this thing to the lake. Also if I remember right I thought I remember reading that the rpms should be 100 higher when on muffs, can someone confirm please, thanks.

 

[Bt Doctur]

TB IV is point and shoot, no base timing setup

 

[Watermann]

If your setting the timing on the boat in your sig line then it's a TB IV with no base mode.

 

[nateo]

Roger. My bad. Same question minus the word base

 

[Bt Doctur]

600-750- or anywhere inbetween works. set the idle speed first, then set the timing

 

[nateo]

600-750- or anywhere inbetween works. set the idle speed first, then set the timing

hum...why would it only stay running at 750? I adjusted the timing last year at 650 and the merc sticker on the engine says 650 idle rpm.

 

[Bt Doctur]

Basically ,the steps are:
remove the throttle cable
adjust idle to between 65750 at normal operating temp
adjust idle mixture screws for the best smooth idle disregarding the rpm .
Check and adjust timing, correct idle rpm if necessary, recheck timing
Adjust rpm in gear to spec or the lowest rpm the motor will tolerate and still run after shifting out of gear IN THE WATER

 

[nateo]

Yes but it should be 650 right? I can get it running on 750-800 but idle rpm is iratic once I put it in water. I don't get any ominous noises coming from this motor when running at the 800 rpm. Just wondering if motor needs rebuilt or might there be something else here at play (other then fuel). Ok I haven't changed fuel water seperator this year I guess it could be fuel but I've burned half a tank this summer just troubleshooting. My gut tells me not fuel related

 

[Rick Stephens]

Are you setting idle speed on a decent shop tach? My own boat tach is what's erratic and impossible to set idle speed by.

Lots of things will make a motor not idle as slow as is should. Everything from valve guides, plugged up carb, fouled plugs. Asking the question: 'does the motor need rebuilding' means you need to run tests to answer it - compression test, vacuum test come to mind as a start.

Rick

 

[nateo]

Are you setting idle speed on a decent shop tach? My own boat tach is what's erratic and impossible to set idle speed by.

Lots of things will make a motor not idle as slow as is should. Everything from valve guides, plugged up carb, fouled plugs. Asking the question: 'does the motor need rebuilding' means you need to run tests to answer it - compression test, vacuum test come to mind as a start.

Rick

Been using my boat's tach. What is a shop tach? Do I just go to auto store and buy new gauge to rule it out or do I get something more unique such as the digital one harbor freight sells? I have done a compression test which turned out within spec. Perhaps I'll do vacuum test next.

 

[Rick Stephens]

I use the tach built into a digital Innova timing light. Also have the same thing built in a Napa timing light. Nothing special, but a good way to double check that your boat tach is even in the neighborhood - mine isn't.

http://www.amazon.com/gp/product/B000EVYGV4?psc=1

 

[nateo]

I use the tach built into a digital Innova timing light. Also have the same thing built in a Napa timing light. Nothing special, but a good way to double check that your boat tach is even in the neighborhood - mine isn't.

http://www.amazon.com/gp/product/B000EVYGV4?psc=1

man that is really cool. I didn't even know those exist. Just bought a new timing light this summer, wish I would have got one of those. I think I might have to upgrade

 

[Rick Stephens]

I've used mine out on the lake trying to get the idle fuel mixture just right and trying to figure out why my idle RPM was too high. All of Mercruisers final adjustments are done on the water, nice to have a very portable tool.

 

[Eric 3.7LX Alpha 1]

You can also use an old school analog meter... I have an old Sears Craftsman diagnostic analyzer that can do many tests like this one

Mine was given from friend never used still in the box.

http://www.ebay.com/itm/Sears-Engin...4e23614&pid=100005&rk=2&rkt=4&sd=281767389748

 

[havoc_squad]

Definitely recommend the timing gun with built-in digital tach, with an adjustable timing degree adjustment option as a bonus.

It takes the guesswork out and you have the RPM's right in front of you. All that is required is toggle the mode (tach mode/timing light mode).

Super easy to dial in your idle stop screw and work with carb mixture screws if you have a vacuum gauge hooked up while in the water, at idle, and IN gear.

 

[flipbro]

?Just do the vacuum test. Then adjust carb and timming to we're you get the best vacuum. If you can't pull good vacuum you've got issues. Then you just diagnosed of the readings you get.

 

[achris]

?Just do the vacuum test. Then adjust carb and timming to we're you get the best vacuum. If you can't pull good vacuum you've got issues. Then you just diagnosed of the readings you get.

DON'T time using a vacuum gauge. That may work fine on a car engine, but do it on a boat and you destroy the engine with timing too advanced. USE A PROPER TIMING LIGHT! Set to Merc spec....

Chris......

 

[flipbro]

That was meant to just get him in ball park to see if his engine is heathy or not.. And if he can pull vacuum then set his timming properly with a gun.I believe he's got bigger issues.

 

[achris]

... Then adjust carb and timing to we're you get the best vacuum.....

That was meant to just get him in ball park to see if his engine is healthy or not.. And if he can pull vacuum then set his timing properly with a gun.I believe he's got bigger issues.

Then best not write it the way you did.... ^^^^

 

[nola mike]

Or even a dwell meter