Horse Trading Lands Me An Older Honda BF100 with issues

[americanmcss]

Hey everyone. Its been a while since I've been in the forum, but this is usually the best place to learn from those who have "been there, done that". A series of buying and selling and trading in boats and motors landed me with a cheap, old, evinrude 25hp tiller, early '70s vintage. It was bought from a retired Evinrude/Johnson mechanic who rounded up old motors and freshened them up with parts he bought from defunct dealers and swap meets. I think I paid 250 for it. It ended up being too powerful and heavy for the transom rating of the fishing boat we acquired so I put it up for sale or trade for a smaller motor. I ended up with a well used, but running honda BF100 4 stroke with CDI. A local guy used it on is fishing and crabbing boat, so it had seen salt water. It was missing the proper kill switch and the throttle friction nut, but it ran very well in the barrel. It wound up in storage after that for a couple of years and I just pulled it out a couple of weeks ago. I had never actually run it on a boat so it wasn't until last weekend that I found out it has serious power issues. I went through and did what I could to clean up the electrical contacts and spark plugs and wires. Greased the moving joints, changed the gear oil and went ahead and put a new water pump impeller in there as well. In forward gear at WOT I could barely get the boat above 5.5 mph. For perspective, our Evinrude Deluxe 4hp short shaft will push the boat at 4.5mph at WOT. I could tell the engine struggled to reach maximum rpm, and I'm guessing we reached only 60-75% of maximum. It would run at WOT for about a minute before it would suddenly die. It would start again right after and run another minute and then die. We did what we could on the fly in the lake with no positive results. Got it back home to the barrel, where it appeared to be healed. I cleaned the fuel filter inside the pump and removed some debris, made some more carburetor adjustments, and adjusted the timing via the timing belt all with positive results. I replaced the kill switch with an aftermarket safety/lanyard style and found an OEM friction nut to install. All in all its a complete, running engine but I need some help.

Anyone with some insight here?

 

[Sea Rider]

You've found the hard way that testing an engine on water at load is a complete different story when tested on a barrel at idle/ neutral. When buying second hand engines best is a wot water trial, if engine is with issues, simply walk away unless you know how to troubleshoot it well or happen to be a mechanic. Could be buying a Pandora engine full of costly hidden surprises.

Happy Boating

 

[Scott Danforth]

you gotta clean the carb if its been sitting for a few years.

no adjustment or mechanic in a can, actually pull it apart and clean up the crud

 

[americanmcss]

You've found the hard way that testing an engine on water at load is a complete different story when tested on a barrel at idle/ neutral. When buying second hand engines best is a wot water trial, if engine is with issues, simply walk away unless you know how to troubleshoot it well or happen to be a mechanic. Could be buying a Pandora engine full of costly hidden surprises.

Happy Boating

Yes, I agree with you 100%. 3 years ago when I made the transaction, It never would have occurred to me to do such a thing. I was a bit more naive, and rather excited to "score" a Honda in trade especially when I was getting rid of a large, unsightly fuel hog of an evinrude. At the time, a running BF100 would sell for $1200 locally, So I kind of figured that was good insurance. I see some locally priced around $800 on Craigslist, but we are just ahead of boating and fishing season, so come June or July it might be worth more. I want to fix it though. I'm into it for next to nothing for what it is (through my horse trading I'm actually about $1300 in the black).

I probably should take the carb off and throw it in some chem dip. I don't have a honda outboard dealer locally so I'm on my own for parts. It looks to me like there's just a mounting gasket and a fuel bowl oring that would need replacing.

 

[americanmcss]

Quick Update...

After much research and fiddling with the engine, I discovered that the timing was indeed off by one tooth. I located a service manual online and began pouring through it. In the troubleshoot section under "Low Power at WOT" the number one reason for that was timing. Its possible that it skipped a tooth but more than likely the p/o screwed with it and didn't know how to re-time it. It was running very well in the barrel which I know is little indication, however it appears that now the carb float is stuck because gas was pouring out of two small ports at the top of the carburetor last night while I was testing it. I was planning on removing the carb and cleaning but after we'd done another water test. We had plans to fish Saturday morning and test the engine again then, but I don't know if I'll be getting my hands on the gaskets before then. I suppose I could try to fake it. The bowl o-ring might be re-usable and I could cut a carb to manifold gasket from stock.