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 Well My Norman has ...............?
 Outboard (pre-1987 Honda 9.9 hp) oil change
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Tom Morgan

106 Posts

Posted - 13 Apr 2021 :  07:24:48  Show Profile Send Tom Morgan a Private Message  Reply with Quote
This will be my first DIY oil change. The manual recommends 10W-40. Will any 10W-40 oil do, or is there any special grading for outboards?

I made a note in my notebook that 20W-40 is also suitable for use in the UK. If that's right, would you recommend one grade over the other?

(I already have the gear oil).

Grateful for any advice, as always.



1307 Posts

Posted - 13 Apr 2021 :  21:03:10  Show Profile Send cliveshep a Private Message  Reply with Quote
If you don't use Honda's own 10w40 other oils will melt all the metal parts and give you covid.

Actually engines are quite tolerant of oils, no tolerance for NO oils though.

I'd use any modern multi grade 10 or 20w so Tesco or Aldi could be your friend for the boat engine much as they could be for your car. Boats get little use anyway so the engine is being spoilt with an annual oil change. Consider how many hours running a car will do for a 10000m service interval to the annual hours for an outboard.

Several hundred hours is more than likely - how many annual hours does your boat run?

Just make sure when you change or top up the lower unit gear-case oil that it is clean and golden, creamy means the seals have failed - those behind the prop and those below the water pump - always change both and give the engine a new impeller while you're at it. Keep the old one for emergencies if it is still apparently good although only a fool doesn't have a spare new one if he's going cruising plus the tools to change it. Impeller failure and over-heating are one of the major breakdown causes and can cause damage to the engine, warped head and head-gasket failures for example.

Finally living the dream!

Edited by - cliveshep on 13 Apr 2021 21:06:13
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United Kingdom
5905 Posts

Posted - 14 Apr 2021 :  02:26:34  Show Profile  Visit df's Homepage Send df a Private Message  Reply with Quote
You will normally find a code for oil specs in the manual for it, the numbers are just the viscosity grade, get one with the same code and you'll be fine (the cheap stuff will likely have the same or newer code on the tub).

NBAS--The communal colostomy bag of the boating community.
Visit leomagill.co.uk
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Tom Morgan

106 Posts

Posted - 15 Apr 2021 :  16:54:02  Show Profile Send Tom Morgan a Private Message  Reply with Quote
Thanks, both. I'll check out the code. I do have a manual for the outboard, but as it's a 35 year old engine, I thought things might have moved on a bit so decided to ask.
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Mad Harold

United Kingdom
166 Posts

Posted - 20 Apr 2021 :  02:58:27  Show Profile Send Mad Harold a Private Message  Reply with Quote
Had a trip along the cut at the weekend,and after a while found my outboard was running dog rough.A lumpy tickover and suddenly racing,and also stopping quite often.
Can only think it is because of stale petrol.Tried to remember when I last refuelles,and it must be a year ago!
Will put a new fuel filter on and refuel with fresh petrol and hope that cures it.
Any suggestions on disposing of 10ltr of stale petrol?
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United Kingdom
77 Posts

Posted - 20 Apr 2021 :  11:28:01  Show Profile Send pete-preston a Private Message  Reply with Quote
Hi Harold
As the price of petrol is high ,sugest you run your car down to half full , pour the stale petrol into the car, then fill it up. That will thin down the stale petrol and the car will hardly notice it .Unless you have a Diesel car !!!! then dont try it
Pete Summerton (KISMET)
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