Mercury 7.5hp blue band

[bigminiandy]

Could I have your thoughts gents.

Have been trying to start the motor with no joy. The engine will cough a little smoke when the choke is across and the throttle is WIDE open but nothing more.

I've changed the plugs and they spark. I've had the carb off to inspect it and make sure all is as it should be and It appears to be correct. The fuel is getting through as once it's been pulled over a few times the plugs are wet.

I haven't touch the timing as the last owner got the motor going a few years ago so presume its in the right place to at least start.

HELP!!!

[haventaclue]

Does the spark snap and jump at least a 3/8th"? Unless the timing was tampered with in the past,it's unlikely to be a timing issue.What is the compression? If all of that is good it's,my guess,a blown crank gasket or seal.
It's true about outboards,a little light use is harder on them than a lot of hard use

[bigminiandy]

Sparks as it should, as you say the timing shouldn't have been changed and it has previously run so why alter it.

I haven't checked the compression, will do that on Wednesday hopefully.

[Rapier]

When was the last time it was run properly? It should run for a sec on choke and 'start' position on tiller, then with choke off should start. If a long while and the compression is really up to scratch, I'd then strip the carb of all needles, floats and other gubbins - clean it and the filter and the hoses (esp if they stink of old fuel). I'd probably order in a new carb kit if it were me and I'd definitely replace the fuel pump diaphram and gaskets, again with a kit. Don't remove the check valves unless you replace them too. I'd probably do all this anyway, as the last thing you need is a day's boating with your Mrs spoilt because a service item has failed through old age.

[bigminiandy]

The motor hasn't run on a boat since 1983 but has been run every 3 - 4 years in a wheelie bin to keep it going. Last ran in 2009.

Having taken the carb off to have a good look at it and make sure nothing was stuck or blocked I'd suggest they ways ran the motor dry of fuel to stop it gumming anything up with storage the float and chamber were like new. None of the fuel lines smelt of old fuel and like you say its worth changing the pump diaphram but at the moment the plugs are certainly getting wet.

Where would you suggest for parts please. Everywhere in the Midlands seems to presume you have a 1.8 BMC diesel in the back of a narrowboat.

Maybe its just me and I'm not turning the choke off quick enough. Next day off is Wednesday so will have a poke around then I guess

[Rapier]

Pity you're not down the road....

Try Duncan Walker Outboards in Reading is the best - may mail out to you. Outboard Spares Unlimited (Maidstone, Kent) and American Marine (ask for Hank 01789-491673) will def mail. Also check ebay..

[haventaclue]

Not really recommended,but you could try a squirt of easy start into the carburetor.If there's fuel on the plugs ,good spark,good compression,there's no reason that she shouldn't start.
Just had a idea,Put it in a box,send it over to me and I'll get it going................Test it for a few years,20 or so, until you forget where you sent it

[bigminiandy]

Will be visiting your shores for next years rally hopefully. Will bring it then for you to get going

If there's fuel on the plugs ,good spark,good compression,there's no reason that she shouldn't start.

thats the frustrating thing. It's all there but no go. Will make certain on the compression with a tester but the motor 'feels' like it has compression

[Alacrity]

A lot of the yanks are in favour of a squirt of premix down the throat of the carb on engines that have either stood a while or just been rebuilt, just for the 1st startup that is. As Rapier says Mercs need choke to get them going from cold, they will fire but stop in a matter of seconds if you don't get the choke off quickly as it chokes itself to death. They will then usually start without the need for choke or just a brief flick if it starts to die until it gets a bit of warmth into it. It is quite possible its just 'finger trouble' & once a) it has run & b) you are familiar with starting it you will I am sure not have a problem in the future. The later 'square cowl' 7.5's did prove difficult to start & there was a definite knack to it but these were always OK.

Geoff

[haventaclue]

Will be visiting your shores for next years rally hopefully

Hope to meet you and a few more of the club members for bit of ,if I get to bring "NO-KIT" a couple and a few and hopefully no