Hi, just bought a trailer sailer with a Mercury 110 (9.8HP Outboard) on it. Does anyone have any idea what shear pin size is needed and can confirm the oil mix is 50:1.
I have an 8HP Merc, which is basically the same as the 10HP. That has a splined shaft and uses a 50:1 mix. How old is your engine and have you checked that it actually does use a shear pin? The oil mix is almost certainly 50:1 unless it is very, very old ..... and maybe it IS fairly ancient because modern motors of that size have a splined shaft and do not use shear pins.....
If it's age is unknown and you cannot get any definite information I would use a 25:1 mix to start with and once properly warmed up, if it smokes a lot, then cut it down to 50:1.
I haven't actually looked yet so it may not have a shear pin at all, I just assumed. As far as the age is concerned then the serial number is 9166904 - maybe someone can tell the age from this?
It is aged 1974 ish I spect. Post a photo for more precise answer. I had 9037331 and that was 1974. The mercury marine website has a page where you enter serial # and it tells you the age but it doesn't go as far back as those mid 1970s 7-digit serial numbers
Oil is 50:1. It has no shearpin, instead it has a rubber bush inside the prop. Good motor /forums/images/graemlins/grin.gif
I haven't actually looked yet so it may not have a shear pin at all, I just assumed. As far as the age is concerned then the serial number is 9166904 - maybe someone can tell the age from this?
[/ QUOTE ]This might sound a bit simple but as you have the serial number and I assume model number, have you considered contacting Mercury either in the form of one of their dealers / service centers or Mercury tech help / customer services via their website. You probably have good advice but for the sake of a phone call to the "people who know" or an email to Mercury, I would prefer to have the information "from the horses mouth" so to speak.
Many years ago in my diving club we had 3 "identical" 25hp o/bs bought over 5 years, one was 25:1, one was 50:1 and the other was 100:1 - nightmare trying to keep control of the fuel mixes.
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Look for Old Mercs .
However it appears that Mercury have different serial number ranges depending on where the motor is supplied. American and Canadian motors have different ranges so you need to ask a European or even British dealer.
Thanks for you help on this - I'll contact a dealer
Another quick question and that is how often would you recommend that the engine is flushed out with fresh water (hopefully not to often as the boat is kept on a swinging mooring and I wouldn’t want take the mercury ashore in the tender!)