BMK 21 On Honda BF 15 Outboard

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I'm thinking a BMK-21 backed up by a TP; you know - to "super polish" the oil. Bypass filter the bypass filter, so to speak. That ought to keep the little 15hp boat motor running ...
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(Said the kill-joy).
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When I think of the octopus that I had under the hood of my beloved minivan (
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a "beloved" minivan - imagine a Witch Hazel pause and a laugh) ..I really would like to see this happen. I keep seeing some Chevy Chase movie where he was moving and got totally ruined every step of the way ..and then ended up with a neighbor that had a V8 powered lawn mower that could do the north 40 in 3 sweeps
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I mean, there are tons of cars out there that are built right out of the Summit catalog. No one really needs 650+hp to move from point A to point B, do they?
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"Need"? No, not need. But "want". Oh, yeah, baby!

Reminds me of the guy on "Dream Car Garage" that does some of the test drives. He always ends his review by stating "Do you need a car like the XYZPDQ? No. But do you want a car like the XYZPDQ? Oh, yeah - you want a car just like this!" I love that. Clearly seperating, and acknowledging, the disparity of wants and needs. It's fine to want things, and even do/get/buy the "wants". But at some point, the "wants" become a bit obscene. Like a bypass filter on a 15hp outboard Honda motor ...
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But I would so be watching; you just can't avert your gaze from the surreal.
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Replace the restrictor plug with a new one drilled to a smaller size to limit the flow a bit more for the smaller oil pump capacity. (.015" sized) Yeah, that's the ticket! And definitely use the cheaper mount, the BP-80A. No need to waste even more cash on the BMK deal. You can get some hose and fittings locally for much cheaper that will work perfectly fine.
 
Originally Posted By: dnewton3
Yes, I realize that there's no filter on this little engine. But the same can be said for hundreds of thousands of little air or liquid cooled engines with either splash or forced lubrication for four cycle engines. And there's obviously no practical way to filter wear metals from 2 cycle engines. And yet, they all just keep on running.

I expect Honda looked at this boat motor, and reviewed the wear patterns, wear rates, and "typical" seasonal use factor, and decided a filter just wasn't necessary for expected long life. I cannot think of any example that I'm aware of, either directly or indirectly, where a Honda engine stopped because of a perceived lack of filtration of it's lube system. Granted, there are plenty of engines that fail from too little or too much lube. But engines that are maintained according to the OEM specs? Nah - you just don't see those fail.

I looked at the Honda Marine website; the owner's manuals are available for viewing online. The older engines (with squarish motor hoods) don't use fitlers. The newer engines (with rounded motor hoods) do use filters. So presumably he has an older one. But I looked at one from each generation (of the four series listed) and observed the following:
they all have about 1.1 to 1.2 quarts oil capacity
they all have OCIs at 100 hours, regardless of filtration system being present or not
they all use 10w-30
So, it seems like the little engine from yesteryear is just about as capable as today's. Clearly Honda thought is was a good idea to add a filter; they would not have added cost and complexity for the joy of it without some ROI. But let's still look at this at face value. Adding the fitler didn't gain any appreciable OCI distance. Same sump capacity. Same oil grades. The OCI is 100 hours or every 6 months, regardless of generation of engine. I already asked the OP just what useage the motor was expected to endure? We have no indication that the 100 hours would even be usurped in a single season. Typically, those of us on BITOG have many engine-driven interests. Even if John-302 is retired and fishes daily, would he surpass the 100 hours in a season? He's probably like the rest of us, and goes fishing one week, drag racing another week, motorcycle riding another week, etc. While he's constantly in a motor driven conveyance, any one of them may not accumulate high usage for the season. Again, he could let us in on his dirty little secret, but he hasn't. So, I am left with assumptions from here on. Is this motor on a small fishing boat? Does it see frequent start/stop cycles? Is it pushing a sailboat out to sea, and only sees infrequent use? Is it used to ferry people to/from houseboats? Inquiring minds want to know!

I have three Honda pieces of equipment. A Goldwing (forced lube). Also a GX190 air cooled 4 cycle on my utility cart (cheap version of a 'Gator), and a little 4 cycle mini-rototiller. The latter two are splash lube'd. Clearly splash lube is inferior to forced lube, in general. And yet, these motor on with no signs of stopping. Just annual OCIs, with no filters.

I don't condem Mr. Beastly 302 for wanting to play and experiment. But he'll be "adding" lifecycle to the "little engine that already could".

He could gut the filter internally, and still take the life cycle out infinitely just because he's probably doubling the sump capacity. Add the bypass element media and he's heading "To infinity, and beyond" (credit Buzz Lightyear!).

And let's look at the cost involved. BMK set-up, plus annual filter costs, and extra oil costs. Compare that to no oil filter, and about 1 quart of the standard sump fill.

Just because he can do it, doesn't mean he should do it. There's just no "percievable" gain to it. My prediction is that he does it for the fun of it. And then a few seasons from now the BMK ends up on E-bay, or some other venture, because he'll realize the time/money/effort spent on this little outboard is wasted because it already will outlive his use for it.

Now, if he's trolling for clams for 8 hours a day, all summer long, and wants to extend his OCI for the sake of the OIL (rather than the motor), that's entirely different. It might actually make sense. But man, that's a lot of time in a little boat ...



I agree that there is no need for filtration on this engine. I have a model year 2000 BF9.9 and it is the exact same engine as the 15 with the exception of the carb bore size being slightly smaller for the 9.9.
So I have had my little 9.9 for nearly 10 years and I estimate that I use it 100 hours a year with annual OC's. It pushes my 14' aluminum jon boat with ease and is mostly used in salt water for area flats fishing. It has been very reliable with only a couple water impellers and a re-hub with a ss prop upgrade in that time.

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Sorry about the messy garage
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This engine still runs and looks like new and the oil does not change color at all on the dipstick.

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So I can't understand what the OP thinks he will be gaining by adding this filtration to this engine and I believe he risks doing more damage than good.
As an aside, I have never seen an outboard engine with an air filter. Why is that?
 
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As an aside, I have never seen an outboard engine with an air filter. Why is that?


There's virtually no airborne abrasives on the water. It's a dust magnet. I personally think it's unwise ..just for random "stuff". We had a screw rattle loose on the carb of a a 120hp Mercury IO in a runabout at summer camp. Sucked it right into the engine. Pulled it out through the spark plug hole with a magnet. The engine was hurting.


There are quite a few outboards with oil filters.

Even one for a 9.9hp Yamaha on ebay. It sorta looks like the inside of a Magnefine (the lower one).

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Man I guess I have sure missed out on some heavy duty filter discussion. Being that I am a college student it is hard to find time for these "projects". But after thinking about what would go into installing a filter on this engine I decided that because I put maybe 50 hours a year on the motor going through this headache is just not worth the headache. Ant how thanks for the discussion anyway.
 
Oh, John
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..you're letting us down here. We were all geared up for endless discussions about the benefits in pure bragging rights. Bass masters everywhere would be envious of your filter setup. Heck, you've just denied SteveS and additional opportunity to tell you the futility of your project.

Here's me and a couple of the guys when we read this post.

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