90hp mercury hard to start

[tiles]

Hi

I have a 2003 90hp 2 stroke mercury 350hrs on clock when starting from cold i have to keep choking it by pushing key in for a second until revs pic up, revs will die down again after about 5 seconds then choke it again this can go on for 2-3 minutes until it will idle on its own any ideas on what could be the problem motor runs and starts fine once warmed up

[Guest Aussie007]

check your fuel hoses for air leaks, are u priming the fuel line with the bulb?

[ving]

How old is the fuel?

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Edited August 17, 2013 by ving

[Testlab]

Try again with fresh fuel and new spark plugs of the type specified, which may not be the type in it. If it doesn't improve it could be anything from a stuck thermostat to idle speed mixture adjustment.

[Geoff]

It's a fuel problem. As it starts & runs fine when hot then it's more than likely the primer bulb or chokes are not working properly.

It's not uncommon for the internal valve to fail. Hold the primer bulb in a vertical position with the outlet upwards , pump the bulb. If not going hard then replace the bulb.

If the bulb is OK , remove the air intake / air filter so you can see the choke butterflies. Activate the choke to see if they are all closing to the same position.

One , maybe more are not closing correctly.

Geoff

Edited August 17, 2013 by Geoff

[tiles]

Thanks all for your comments

The bulb pumps up hard

Plugs ill check and change i think as 2 strokes love fouling plugs up

Ill check the butterflies Geoff as that definatley makes sense

[tiles]

Just pulled airbox cover off only seems to have a gasket seal around the bottom and up about 25mm each side, gasket looks made that way doesnt seem rite unless it comes in 2 parts and the rest has disapeered??? also cover has 3 holes in it i think thay are to look inside carbies without having to remove cover, 2 have removable pluges in them the top 1 is open this should be pluged to i would think ill start with fixing that first and see how it goes

[The Incredible Hull]

Before you start the motor, have you tried edging your throttle forward a little bit?

[tiles]

Yep tried lifting idle lever a bit just revs higher then dies down until i choke it again

[tiles]

Just replaced airbox gasket turns out it is only made for bottom section,replaced plastic plug missing from front of box, also put new spark plugs in BUHW-2 the ones that were in it were champion QL16V

[tiles]

(continued from above) was a bit worried because the new plugs were probly 3mm shorter it didnt seem to mater i turned the key an she fired an ran straight away didnt have to choke it at all can any one comment on the old plugs were thay the rite ones and about the length difference between them

Thanks

[Testlab]

NGK BUZHW-2 is the correct plug but the BUHW-2 is probably OK as you may not need the inductive resistance (the inductive resistance reduces interference that can affect the ignition system or ECU).

I think the equivalent Champion is a QL78V. Are I sure it wasn't a QL76V that was in there before?

Edited August 24, 2013 by Testlab

[tiles]

Plugs were definatley QL16V thay were fitted by a boat mechanic at its last service thay must have been old stock he was trying to get rid of because we couldnt find them in the plug book, i did ask about the z plug the bloke at the boat shop said BUHW-2 would be fine for my motor, think ill look into the z plug a bit more before i take the boat out tho

[Geoff]

Tiles. Whilst the plugs may have been incorrect & new plugs have made starting easier , I go back to your origional post where it is OK when hot but not cold.

" When starting from cold i have to keep choking it by pushing key in for a second until revs pic up, revs will die down again after about 5 seconds then choke it again this can go on for 2-3 minutes until it will idle on its own. It runs and starts fine once warmed up."

I don't claim to be an expert on plugs but I have never found either in cars or outboards that plugs cause the problem you decribed.

From my experience the reverse applies , plugs brake down when hot or under high load not when cold.

I'm happy to be corrected if wrong.

Plugs appeared to have helped but I would still be a bit nervious about the fuel system.

Geoff

[tiles]

Plugs were pritty fowled up Geoff will still get a new bulb and a mate is going to check the butterfly settings out for me let you no what we find

[GaryO]

Keep us posted Tiles, my motor has similar starting problems.

[tiles]

Checked the butterflys were opening and closing evenly today all was fine

Pumped the bulb up turned the key and she fired straight away and ran perfect

Im prity sure it was bad plugs how have you gone GaryO have you got yours sorted yet

[austral]

we have the same motor and to start ours, I always lift the throttle all the way up then push the choke in as I turn the key and leave the choke in until it starts. works every time..

maybe your just not leaving the choke on for long enough..

[tiles]

I dont touch the choke at all now just turn key and she starts an will sit there an idle touch wood

[GaryO]

I have run it Tiles but havnt checked anything as yet.. Mine starts easy but will stall if I dont push the choke in every 5 seconds or so, it will run how ever if I raise the idle lever up quite high. After about 30 seconds it starts to run ok at normal idle speed and will start and run perfect for the rest of the day. I plan to at least change the plugs and see how it goes.

[GaryO]

Bugger !! Changed the plugs Tiles but I didnt have your luck It still runs the same. At least ive ruled that out.

While im here I might ask if anyone can give me some advice on gear oil replacement. ive just changed it but the amount I drained and the amount I put back doesnt seem to be anywhere near the 450mls mentioned in the specs, I put in about 300 doing it correctly via the bottom hole up .?

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[dunc333]

hi not sure what gear box you have on it ,the 83mm diameter gear case takes 340mls,the 108mm gear case takes 655mls acording to my merc book hope this helps cheers dunc 333

[GaryO]

im not sure of the size but im just going off the manual .

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[tiles]

Shit thats no good Gary mite be time to let someone have a look at it

[Testlab]

Gary, does it run at idle ok when warmed up? Or does it miss occasionally? It could be the low speed mixture adjustment if it has the odd miss or the carbys are out of balance. Unless you're familiar with carby adjustment let someone who knows what they're doing sort it out.

Edited September 7, 2013 by Testlab