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Oil viscosity 2003 bf 225a's

S

sea bee

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I saw the Chalk_man’s post of 6/22/2015 on oil viscosity and I’m thinking about making the switch to Mercury Marine 25W-40. I am currently using Honda Marine SAE 10W-30 in my 2003 BF 225A’s that have about 1250 hours. We do a fair amount of tuna fishing which means a run of 2.5 hours each way at 4000 RPM’s. After about 40 hours (about18 hours running 22 trolling), I needed to add a little over 1 Quart of 10W-40 oil to each outboard.

When I make the switch, is it advisable to add 25W-40 to my 10w-30 oil when needed or should I wait until the end of the season when I change the oil? (100hours). Any comments or recommendations would be appreciated. I’m in NJ and run very little in cold weather (launch in April, pull in the beginning of November).
 
Even using 10W-30 oil, you shouldn't be using that much oil. No problem with adding 25W-40 to the 10W-30, IMO. Others may disagree.

Then when you do a complete oil and filter change, go completely to 25W-40.

However, at the end of this season, I would highly recommend doing a de-carb, which should loosen up the rings and help the valves seat better. Good practice says to do a compression check before the de-carb, and another after the de-carb, to see what improvement was made.
 
Chawk Man, I also thought that was high useage and it bothered me both engines were down about the same and that I didn't have an oil problem last year. I then realized that some of it could have been from changing the filters and not rechecking the oil level after starting. In any event, I know the level is now correct and I will monitor it from this point. I agree the compression check and de-carb at the end of the season is a good idea even if there is no consumption problem. Thanks for the input.
 
Yep, I didn't think about that.

On most engines, you try to fill the filter with oil before installing. On the BF 225, that's darn near impossible and results in an oily mess. I put the filter on dry, then fill it with 8 quarts, even, start the engine and let it idle for at least five minutes, and recheck and top off the oil level.

The manual calls for 8.2 quarts when you change the filter. But I have found that no matter how well you drain the oil, there will be some residual oil left in there. That's why the 8.0 quarts. It's a lot easier to add a little oil after the filter is soaked then to try to drain some out.
 
Chawk man, Now that I'm into the Mercury SAE 25W40, i'm getting confused since Google comes back with Quicksilver and Mercury SAE 25W-40 synthetic.
What are you using?
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