BF8D 2001 Cylinder Head hole

[BrookerV12]

Have a 8hp Honda that I bought a little while ago and want to try and get it back to good working condition. Has a bit of a problem with cold starts but that is something else to work on. While checking and adjusting the valve clearances I noticed there is some sort of hole down in the bottom left of the head. It just doesn't look right - is it by design or is it the result of some sort of damage? The hole in the bottom right looks factory and assume is something to do with oil flow. If it is damage would it affect performance? Haven't taken the motor on the water yet as just finishing up the servicing. This is the first time doing maintenance on an outboard like this so any info about this would be appreciated!!

 

[jgmo]

Hi,
Sorry no one has answered you yet but I was waiting for someone that actually knew what they were talking about to give you some advice. I just wanted to let you know that you're not being ignored.
Maybe everyone else is in the same boat as me.

I can't believe I don't know this....I should! But while I have had many valve covers off of many 8 hp Honda outboards, I don't recall giving the oil return passageways any thought. You know....open 'er up, adjust the valves, move on. That's my excuse anyway.

I agree with you! That spot looks gnarly! Just like something banged through there.

But looking closely I don't see any signs of anything touching or banging into anything else nearby.

And judging from where the hole is located it seems the logical spot for an oil return to sump. There even appears to be a channel in the casting pointing downward right next to it.

If you've been running the outboard with no I'll effects and you can't detect any air flow going into or coming from the hole when you pull the engine over I'm thinking it's the drain.

I do recall seeing funky aluminum casting flaws that remind me of damage so, maybe, that's what you've got there.

Try draining the oil, leave the plug out and then pour some oil in that hole to see if it comes out the oil pan. If so, I would carefully clean up the edges of that spot that look like they might break off from vibration and put it down to a foundry mistake.

Or...maybe me bumping your post will get someone that knows for sure to answer up.


Good luck.

 

[jgmo]

As far as the hard cold starts....is this a pull start or electric start?

The reason I ask is that the pull start has a "choke cable" while the electric start model has a "bystarter" that is automatically controlled with voltage from the stator coil.

As you may already know, there is no conventional choke "butterfly" at the entrance to the carb throat. This outboard has a "start enrichment" circuit in the carb instead.

It basically consists of a circuit that allows additional fuel to flow during cold start and is then closed as the engine warms.

The auto system on the electric start model is defaulted to "enrich" and then closes electrically a couple of minutes after the engine begins running.

The choke cable on the pull start models can be problematic when they age. The interface between the "SE valve assembly" and the cable gets sloppy and can cause less enrichment when the cable is pulled fully out. If you look closely at where the cable enters the valve boot you may see cracks. Watch that spot as you manipulate the cable in and out and see if it looks like something is moving under the boot. If, so, you may not be getting full enrichment during cold start. In that case I recommend replacing the entire assembly WITH the cable. See items 15 and 20 in the link below.

https://www.boats.net/catalog/honda/outboard-by-hp-serial-range/8hp/bf8d1-lha-2001/carburetor

Good luck.

 

[BrookerV12]

Thanks for responding - the hole does look strange with the jagged edges but looks like it is all painted nicely - can't see any bare/damaged metal or any fragments so maybe as you said a casting issue. Couldn't find any pictures to compare against so maybe if someone has the same head lying around they could have a quick look - the 9.9hp appears to have the same head as well.


It's all back assembled now - did a test in a water bucket and it actually started up quite quickly - this time I kept the throttle a little bit higher than idle when starting and it seems to like that better. I may have also been flooding it previously thinking it wasn't getting enough fuel. It's an electric start with auto choke - I had taken apart the carb and cleaned it out, replacing gaskets and o-rings, also tested the bystarter using the 12v method and checked resistance was in spec.


Hoping to take it out this weekend for it's first real test run as have finished doing as much home servicing as I can do. Will put a response down if there are any further issues! Thanks again for your response and information..

 

[jgmo]

Well, the auto bystarter usually works very well without any need for cracking the throttle. At least it has in my experience with them. But, then again, I live in Southern California, where the sun always shines, there's gold beneath your feet and the the Governor is always being recalled;>)

If it works for you then it works.

But if you do continue to struggle with cold start ups, then you may want to check the compression and ensure that it hasn't decreased too much. If the outboard was used to troll extensively before you got it, it may have built up some carbon. Often you can do a chemical decarb process or even use water spritzing to break that up and get an improvement.

Until then just run her WOT a good bit and keep her throat clear.

These Honda "D" twins are some GREAT outboards and I hope that you have a wonderful experience with your... new to you.... purchase.

 

[BrookerV12]

Took the motor out on the water last weekend, no problems at all. Started straight up, idling fine and throttle pickup and at WOT runs great! Did a bit more looking around and found pictures of a BF20 head which has the same type hole in question, and the picture on the other side of the head shows some sort of gallery so looks like the hole is actually by design! thanks for all your responses.. Cheers!

 

[jgmo]

Sounds good and that you're happy with your Honda.
Around here, that's all that counts!
Thanks for the update!