Merc 7.5hp starting issues.

I have a late 70's vintage Mercury 7.5 2 stroke that never wants to start on the first, second, or fifteenth try. I pull and I pull, I prime, I play with the choke. All to no avail. It's almost like it finally gives up on me, has sympathy and then starts. What am I doing wrong? Also, when I watch the fuel travel through the clear line to the carb, while it's running, I notice a lot of bubbles. Is this normal, or is air getting in somewhere where it shouldn't?<br /><br />Any advice will be agreartly appreciated.

Re: Merc 7.5hp starting issues.

There should be no air bubbles in your fuel line. You have a bad connection somewhere or bad tank. Check all the connections and be sure the fuel line is soft and pliable. If it isn't, replace it. I assume the clear line is just for testing purposes?

Re: Merc 7.5hp starting issues.

I forgot to ask if you have ran a compression check?

Re: Merc 7.5hp starting issues.

Bill,<br />Thanks for the reply. The clear line actually runs from where the fuel line connects over to the carb. If feels rather pliable. The compression was run by an outboard shop last Summer and all was well. I forget the actual numbers, however. It had a full tune-up a few seasons back, and was deamed a good little engine. When it runs, it seems ok. Just hard to start!!!

Re: Merc 7.5hp starting issues.

This motor is very similar to my 9.8 I'd wager. Start at the fuel tank and check everything to the carb:<br /><br />take out fuel pick up hose in tank and clean screen and check hose. Replace screeen and hose if they're not perfect. <br /><br />Check connectins at tank. No air leaks.<br /><br />Make sure tank is clean and fill with fresh fuel and oil.<br /><br />Check entire fuel line from tank to engine, including bulb. Replace if you have any questions at all. Again, solid rubber, no air leaks, etc.<br /><br />Same with connection at engine and fuel line from connection to carb. <br /><br />It's cheap and easy to replace the rubber hoses and bulb if necessary - don't hesitate to do it if you question this at all.<br /><br />Check and clean fuel filter (probably right at carb).<br /><br />Check operation of choke butterfly.<br /><br />If this doesn't help, the next thing I'd do is check the spark plugs and spark (do a search on spark tester, it's easy). If that checks out and it still doesn't help, then the next step I'd take is to completely soak and clean carb and do a carb kit (gaskets at least, entire rebuild kit if it isn't too expensive).<br /><br />Good luck.

Re: Merc 7.5hp starting issues.

D,<br />Good sound advice! I will try all above mentioned. I'll let you know what I find. Starting to pull my shoulder out starting this thing.<br /><br />Cheers.

Re: Merc 7.5hp starting issues.

D,<br />It appears that if I hold the choke fully out (butterfly closed fully) that I get a much easier start. It seems that the spring is worn, or out of limits just enough to not allow the butterfly to close totally. That helped with the starting issue. Still need to attack the air bubbles in the fuel line.<br />Thanks again!

Re: Merc 7.5hp starting issues.

The choke on my 9.8 stayed open a crack when I first got it too. On my engine (maybe yours too), there is a cable running from the choke pull-knob to the carb-choke bracket. The cable is attached at a fitting on top of the carb. I was able to loosen that fitting, turn it slightly, re-tighten. This resulted in the choke buttefly closing tight when I pull choke knob fully out. Made a diff. in starting. Easy adjustment.

Re: Merc 7.5hp starting issues.

I'll definitely try that! I saw the fitting, and agree that it doesn't look too hard to fix.