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Honda bf8

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Dirtautoguy

New member
Hello. This is my first post here, and potentially hopefully more.

My dad has a 14ft alumicraft John boat with a bf8 Honda motor. Iv kinda taken over the maintenance of the boat and have been using it lately after it sat for about 10 years.

We just bought the motor last year from a guy that supposedly just had a bunch of work done to it. We took it to the lake and it ran like poop…. It wouldn’t idle, it would cut out randomly, and would be really hard to start. (We had to row back)

From what I can tell the “work” that was done to it appear to be gear oil and motor oil changes….

I turned up the idle a little, put new fuel lines and filter on it. I also fixed the choke linkage that was not allowing it to fully choke.

The motor now starts pretty easily usually and idles maybe slightly high. But the issue is it will not rev up into high rpm. It’s like I’m only getting about half rpm’s out of it. The last 1/4-1/2 throttle doesn’t change very much.

I’m not 100percent convinced both cylinders are firing but I know both cylinders have compression and It does run pretty smooth for there to be a dead cylinder.

Another thing that I’m not sure if it is a problem or not is how much water is supposed to pee out of it while running? There is a small stream but I feel like there should be more but again I’m fairly new to boat motors. My dad swears it stopped peeing once while we were on the lake and shut it off. But there was always water coming out when I looked.

I’m not new to mechanical things but I am new to boat motors and I have a basic understanding of carburetors and Iv cleaned a few bowls/jets etc. but I haven’t adjusted many.

I have a couple thoughts about the issue.

Dirty jet?
Throttle linkage?
Fuel pump?

I have some ideas but I thought I’d pitch it to someone who might know more than I do…..

Thanks
 
Hi,
You didn't listen a year model or frame number so I'm assuming a pre 97.

Don't really know where to start on this one but making sure it's not going to overheat is probably the best place.

If it sat for 10+ years, it's likely that it will be wanting the waterpump serviced soon and maybe a new thermostat.Time and temperature changes take their toll even while just sitting. Especially on things made of rubber.
You DO NOT want the water pump impeller vanes cracking and breaking off pieces and then getting jammed up inside the cooling passages. They can be very difficult to backflush out. So, servicing sooner than later is advisable. The standard is every 2 to 3 years depending on usage.

The external cooling hoses on these can get rock hard over time and get choked up with mineral deposits. They tend to catch debris and deposits easier when hardened like that. Plus, outboards that have been stored a long time often have critter nests in places like the water check hose and crankcase venting system. They don't sell hoses for these anymore but it's pretty easy to make your own.

The thermostat is still being sold but is $40. BUT...that will seem cheap if you need one and find they've stopped selling them. Which, could be any time now.

As an example, the fuel pumps were rebuildable but the parts are no longer available.

There is a little jam screw on the carburetor throttle arm linkage that allows for minor linkage changes. It can come loose so check that.
These carbs are super simple and easy to hose out with carb spray. There's an idle circuit jet you can clean without removing the carb.

You could be right about it running on only one cylinder. The twins are famous for starting and running on only one hole and it can be surprisingly smooth when they do.
A cylinder contribution test might be needed to verify if that's happening. You'll want to remove and inspect the spark plugs and apply dielectric (tune-up) grease to the inside of the boots. It seals them as well as makes them easy to pull off and put back on while testing.

Authorized shop manual and parts book available from Honda here:

Honda Marine | Shop Manuals Publications | Honda Power Products Support Publications

publications.powerequipment.honda.com publications.powerequipment.honda.com

You can also look up parts and buy them at www.boats.net
They stock anything still available directly from Honda and usually at a lower cost.

If you have no information about when the valves were last adjusted; I highly recommend that you check them along with the condition and tightness of the timing belt. Check that valve and ignition timing is correct too.

Happy to discuss with you and welcome to the forum.

Good luck
 
Thanks for the replies. I’ll check those out.

I’ll rephrase a little. The boat sat for 10 years my dad has owned it since the 80s. The motor had work done to it just before we bought it last year

I also forgot to add that the belt appears to be new.

The motor will rev higher in neutral than it will in gear. The gear select limits the throttle while in neutral.

I’ll check out those websites

Also another issue we’ve had is testing the motor. We got a Honda part that allows a hose to be hooked up to it so it can be ran but this doesn’t allow it to be put in gear.

I wondered about getting a barrel or something of that sort for home testing?
 
Yes! Absolutely use a test tank (plastic trashcan) for testing and flushing. You usually need to modify the trashcan a bit to use one easily. Make sure that the anti ventilation plate is 4 to 6 inches under the surface of the water so the waterpump can easily prime and move water.

You also need to keep an eye on the water temperature in the can as the hot exhaust water will heat it up pretty rapidly. Adding cool water during extended run time might be necessary to avoid overheating the engine while testing.
 
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