Having Carbs set up correctly??

[Ian MacAulay]

Afternoon, I have a 4.3 mercruiser carb'd engine. Im not up on carburettors to be honest and no nothing about them. But having not long had the boat is it worth having the carb checked and set up correctly, to make sure its in tip top form for right mixture and performance? Also does the timing need to be checked...if so should it be done regular?

My limited knowledge is all with more modern ECU controlled engines that tell you if something wrong with a light or a buzzer

Thanks

Ian

 

[moonraker 36]

just take out a spark plug or 2..
if light brown in colour she's running sweet..
if black and sutty..then get it check over.

https://www.youtube.com/watch?v=8_jkxq5HrZw

dosn't matter that he talking about a bike the principal is the same for your engine.

 

[lynall]

Proper term is plug chop, probably not so easy to do on a boat as you need engine pulling hard then kill the ignition.
But if it starts and idles fine, pulls well I wouldnt touch it, if you find the carb make then get googling wealth of info out there.

 

[wipe_out]

Carbs are generally setup my the manufacturer with the correct jetting etc.. Unless you modify the engine or change the carb it will always be right.. What gets changed when you "have it looked at" is the idle settings.. While the idle mixture does affect the mixture trough the rev range it's not that relevant at the levels of throttle opening that boats tend to run at.. In cars where you run a lot of the time with very small amounts of throttle it's more relevant..

Definitely make sure your timing is right, this can make a big difference if it's wrong..

As Lynall says, if it starts easily and pulls well it's probably fine..

 

[jimmcgee]

find the size of the spark plugs and get one of these :encouragement: , http://www.ebay.co.uk/itm/like/1307...3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108

 

[lynall]

find the size of the spark plugs and get one of these :encouragement: , http://www.ebay.co.uk/itm/like/1307...3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108

Really only any good for setting up idle mixture.

 

[Ripster]

IMO there are two main checks. One has been discussed - mixture and its status at different RPM, throttle levels and load. Then the balance (assuming there is more than one carb) between the carbs - this can make a hell of a difference if its out. We used to use vacuum gauges to check this in my bike days. I don't know this engine, but if there is an air filter, make sure its clean and clear. As others have said, firstly get the engine nice and warm and then run it for say 5 mins at cruising revs. Then shut down and switch off quickly as you can. When its cooled a bit, whip the plugs out and look at the colour - should be a nice mid brown - white and you are weak (too much air/not enough fuel) black the opposite. You don't say if its got any issues, a hole in the acceleration or a stutter or hesitation anywhere. If it pulls like a train, doesn't poor out black smoke and runs smoothly up the rev range, its prob fine.

 

[lynall]

The v6 are double barrelled carbs and I think the v8 4 barrelled jobbies so basically one carb.
Nothing like motorbike ones, I used to use the old mercury column gauges for balancing them.

 

[moonraker 36]

dont think anyone is saying he as motor bike carbs..
just that you can get a fair idea if the engine is happy by the colour of the spark plugs.
(and some v8's are also 2 barrelled!!).

 

[markspark7]

i had my set up by a mobile mechanic on my volvo pentas after previous owner had fitted a car distributer, and he wondered why he could get the timing set! runs spot on now , well worth £200 sovs.