problem with starting

[stevel3]

I have an 05 model 75 hp Mercury 4 stroke that has become difficult to start. It will usually fire almost straight away but wont idle and stalls, then it take ages for it to start again. The last couple of times it has killed the battery and I have had to use a substitute to start. Once it has been running for a few minutes it fires up perfectly again. I am thinking it might be the choke as once warm no problem. I have just had the battery tested and it is stuffed so a new one will be bought next week. My son inlaw is a car mechanic and he tested it for me, luckily he has connections with a battery mob that will look after me price wise. The motor was only serviced about 12 to 15 hours ago when I bought the boat from a dealer at Burleigh, cheers Steve. ps the motor only has just over 240 hours on it.

[FishHunter]

is it carby or injected? Injected motors dont have chokes the ecu controls the start and warmup based on info from the engine temp sensor.

[stevel3]

carby model

[FishHunter]

Does it pump black smoke out once it starts? If it does its flooding.
Take the airbox off and hit the choke button and look if the choke butterflys close, if they dont find the problem, if they do, once the engine starts try giving it bursts of choke and see if that keeps it running. If doing that improves the problem then its running way too lean and has a airleak or the carbs need attention.

[Angla]

If the battery is poor then that could be your problem.

Other than that, have you tried a new fuel priming bulb.

These sort of problems are those testy little ones that pop their head up now and then to test you

Cheers
Chris

[trueblue]

is it worth running some fuel cleaner through for a tankful to clean the carbies?

[robothefisho]

If your battery was stuffed that will be the issue. Motors hate trying to start when not being cranked fast enough.

[Dignity]

What sort of waranty did you get with the sale, might be worth trying the dealer out, he might even replace the battery.

[stevel3]

thanks for the replies, I use Castrol fuel doctor in the fuel which is supposed to keep everything clean. I have had the boat for more than 3 months and that was the warranty from memory. My son inlaw seems to think that it might be the battery so I will see if a new one fixes it next week. It doesnt blow any smoke on start up so probably not running to rich. If the battery doesnt fix the problem I will see how I go looking at whether the choke is working properly or not, this is still my suspicion, thanks again everyone.

[stevel3]

put the new battery in this morning and once I remebered to use the prime bulb it started, it seems to be idling a bit better as well now. This battery is a little bigger than the last, not in size but in cranking. The old one was around 570 from memory and the new one is over 700. Hopefully this was the problem, time will tell.

[Angla]

It would be a great result if that is all it was. Thanks for the update

Cheers
Chris

[Dignity]

Lets hope that is all it is, my missus has a Nissan Tiida and same thing, would sometimes not want to start, turned out that the electronics say "not enough cranking power, don't start" wish it would display this as it had us going for about 6 weeks, would work faultlessly for a week then just crank, crank crank and nothing, didn't even sound like there wasn't enough juice in the battery. The smarter the manfacturers think they get the dumber they are in displaying faults.