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2003 Honda bf8 motor/head rebuild help/suggestions

R

Ryan David

New member
Hello everybody, first post. Novice boat guy, from north jersey. I just recently punches a 2003 Honda BF8 8 hp in "as is condition" for $400. Going into it I knew it had a stuck valve and although I'm not to familiar with the inner workings of a motor, I've got a dad who can hold my hand for most steps that has been working on all sorts of motors and cars and motorcycles his entire life, but I do have a few questions while I'm waiting for my clymer manual.

So to begin I figured I'll try shooting a little pub blaster and unstick valve, of course no cigar. We took off the head, bag and tagged all boats etc etc. and once we got into we sure enough found both exhaust valves were bent 6 ways to Sunday and one of the valve guides is broken (more on that later). The intake valves seemed to be strait, but we're going to replace all 4 because we're already going this far. The cam, rockers, springs all seem fine. My first questions are, which way do the guide valves come out, from the top or bottom? Or is this advised to have a motor shop do? I figure I will need to order all 4 valves, the seals for the intake valve, should I replace anything else I'm over looking?
Luckily the Pistons look pretty good, minor scratching on the lower piston where it hit the stuck valve.

Im also wondering is Honda marine . Com the only place to buy all the parts I need? Can anybody recommend a reputable site I can order all my parts from?

- any general advice or tips to check or replace "while I'm in there"
 

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I don't know a thing about the BF8, but there are several experts on that engine who monitor this site.

One thing - when it comes to Honda's, the Clymer manual is normally full of errors and omissions. Best spend the bucks to get the official Helm shop manual. They are available through eBay and Amazon.

Many folks on this forum use boats.net for their parts purchases. The have good prices and very good parts diagrams.

http://www.boats.net/outboard_motor/Honda/parts.html
 
Thank you for reply, ordered the official Honda shop Manual from Honda. And boats.net was fantastic. Thanks. Hopefully one of those guys'll will reply with some tips and advice.
 
Excellent advise given on boats dot net, I have used them for years for both my Yamaha and Honda BF-100. You will find the Honda Factory Service Manual to be excellent.

Looks like your engine must have lost its Timing Belt while running as it's an 'interference' engine. Did it have a new belt when you bought it?

I would recommend bringiig your head into a trusted Machine Shop and have them surface the head and do your valve seats and lap the new valves for you. You can expect a bill above $100 for this work, but get estimates. Recheck your valve tappet clearances after it's run a while.

You should at least check and probably replace your water pump impeller, the housing for it is also an "On Condition" item. Not necessary for pump, but it would also be advisable to drain and fill your gear case with Hypoid 90 Gear Lube.

Others here have advised against synthetic motor oil in these engines. Use only the "NGK" brand spark plugs. WM and boats.net have them.

You would need the two gaskets to remove the Manifold and check your Thermostat, as it should be done periodically for preventative maintenance.

Make it a habit to use that easy valve to drain your carburetor after each use, leaving gas in the bowl (running dry while flushing does not fully drain it) can cause unnecessary carburetor cleaning maintenance to be needed.

You have a really great little engine, I have enjoyed my earlier (1986) version since 1997.:cool:
Art
 
Thank you for the reply and advice. Will it be an issue only replacing the 1 valve guide that broke? I only ordered the one I need, not all 4. But will definetly have a shop go over the head.

When we pulled the exhaust and inlet manifold the thermostat was 100% blocked, and totally corroded, along with majority of water jackets totally caked with calcium.
 
I would defer to the Machine Shop for that question.

Parts like that are inexpensive in relation to the extra labor involved, should you need to go back in later.
Art
 
I agree with everything Pilotart is saying.

Since the water passage was so clogged, it had to have been overheating.

If you do not have the tools, it might be worthwhile having the machine shop check the surface of the block also for any warping.

Mike
 
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