BF75 No Circulation

I just bought a sailboat with a Honda CDI BF75 4 stroke motor. The boat had been sitting for several months with the motor stored in the cabin. I test ran it before going to the lake and there was no coolant circulation so I took it to the local marina. They service Yamaha, but there wasn't a Honda dealer near me. They called me today and said that the tube and the thermostat was all full of corrosion and basically closed up. Apparently the previous owner had it in salt water and put it away without properly flushing it. The marina mechanic said that they don't have Honda parts so they didn't want to get too crazy about dismantling it, but they cleaned out the parts they could get at without disassembling the engine, and now they have water circulation. He said he is concerned that there may be blockage in the motor where he can't get to it, so it might overheat in part of the engine despite the fact that water is coming out of the indicator. My question is, is there a chemical that could be used to safely flush the cooling system and eat up the rest of the corrosion (if there is any) or do I have to take it to a Honda dealer to have them dismantle the engine?

IF you have one of these hi temp t'stats, a once a year flush won't do. If you find a way to flush this engine after every use on the boat... let me know !

re: "and said that the tube and the thermostat was all full of corrosion and basically closed up....they don't have Honda parts so they didn't want to get too crazy about dismantling it, but they cleaned out the parts they could get at without disassembling the engine"...

Curious... How can they tell the t'stat is "full of corrosion" without taking the engine apart? FYI... I just finished a T'stat replacement job on this exact same engine this past Sunday. It's either an easy job or a real b##ch... depending.... If all 7, 6mm intake manifold bolts come out without breaking, its an easy afternoons job. If one or more break.... its a real pain as you are looking at cheap magnetic S/S bolts in an aluminum head. Total parts cost is under $50 BTW and readily available... My guess as to the real reason they don't want do this job is that if a bolt breaks the labor cost will be thru the roof and they are afraid you will walk away from the engine. I had one bolt seize so badly that a broken bold extractor would not move it and I had to drill/grind it out with a dremel and then drill ( 1/4" drill bit in a hand chuck, turned by hand!) and tap it for a "Heli-Coil" insert. BTW...The only part they could get at without dismantlement of the engine involves snaking a wire back up the intake manifold at the point ( only about an inch) that the indicator hose connects to intake manifold!

If they got water to circulate, then your best bet is to put the engine in a tank/tub ( remove prop for safety!) and run it with a product like "Salt-Away" (See label instructions) Don't bother with their kit which includes a mixer widget that fits on a garden hose, as there is no way to run this engine from a hose.

The way the engine is internally plumbed, water coming out of the indicator hole is a fair indication that all is ok internally. That, and water out the exhaust pretty much covers all the path. I've been thru this drill twice on my engine and 99% of the blockage occurs near the t'stat and in the passages in the intake manifold.

Re:.. "Apparently the previous owner had it in salt water and put it away without properly flushing it."
Maybe so, HOWEVER the stock t'stat on some of these early engines had an operating point that was not suitable for salt water operation and was a 100% guarantee of salt and mineral deposits. Also... the engine does not lend itself to daily flushing

At this point in time, so long as it is being worked on... replace the water pump impeller. Best to buy the HONDA OEM manual for this engine. If you aren't mechanically inclined, find a HONDA dealer for this.

The other weak point on this engine is clogging of the carb jets (especially the idle one) due to ethanol related problems.

Short term minimum tool fix is the run the engine with a product like the one I mentioned ( or a better one if anyone has any suggestions!). Run the engine for awhile and then take the cover off and check if any part of the engine (block, head, or intake manifold) is getting too hot. I like the "spit test"... i.e., spit on part of the engine and if it sizzles or dries immediately... too hot. Conversely, dip your finger in cold water and put a drop on various places. Or spring for a surface temp gauge.

Thanks for the helpful information sandkicker. Sorry I wasn't more clear in my explanation of what they did. When I said "without disassembling the engine" I meant taking the head off. I picked up the motor today. I went over everything in detail with the mechanic. I figured for the $140 bill he owed me a detailed explanation of why he couldn't fix it. He said the impeller and the tube coming from the pump looked like new, but that there was no circulation so they took off the cover over the thermostat. He said under that cover it was completely corroded closed and nothing could get through. He said you couldn't even tell it was a thermostat until they scraped away the crud. He removed the thermostat and cleaned it up, heated it to make sure it was opening and closing properly, and then scraped out the channels as much as he could reach around the cylinders with a screwdriver. They didn't have gaskets for a Honda so they didn't want to remove the head. They cleaned it up as best they could and reassembled the cover over the thermostat. After that they had water coming out of the telltale, but after running for a while they said that measuring it with an infrared detector they were seeing too much heat. They think possibly the channels are restricted or closed and preventing proper circulation in the head and block.

I'm fairly mechanically inclined, so I think I will give things a go here. I live in the middle of nowhere so I usually have to be pretty self-reliant. I'll order a shop manual for the motor. I have a digital infrared thermometer and a personal machine shop of sorts - CNC lathe, manual lathe, CNC milling machine, welders, bandsaws, presses, grinders, etc. I was going to let the "experts" at the marina handle it, but there isn't a Honda one within an hour of me and the one Honda place I called wasn't interested in fixing mine if it had salt corrosion in it - just wanted to sell me a new one.

I think I like your chemical solution as a starting point. I think I'll try that before anything and see what it gets me. According to the mechanic at the marina the temperature on the infrared shouldn't go over about 140 degrees once I have the issues resolved. Does that sound about right?

Re: the stock t'stat on some of these early engines had an operating point that was not suitable for salt water operation and was a 100% guarantee of salt and mineral deposits.
If that is the case, once I solve this problem (assuming I solve it and don't wreck it) what temperature thermostat should I get to make sure this doesn't happen in the future? I will definitely be using this in salt water once I get the bugs out of this boat...

Thanks again for your advice.

Per the HONDA Shop manuals... there are T'stats that open at:
176 F (STANDARD on engines below S/N1004085)
158 F ( standard on engines from 1004086 to 1009156)
158 F higher lift than earlier one at same temp ( standard on engines from 1009157 to 1600000) I think there is a misprint in the manual as the manual says 170000 but then goes on to say that there is a low temp that is
140 F....standard on 1600001 (?) with a lower lift.

I made sure I got the 140 degree one for my engine. The one I took out of mine had a an intake manifold/tstat housing that looked much like yours (a mess) was the 176 degree one. This was sold to me by a HONDA dealer several years ago who was located between a salt water bay and the Atlantic Ocean...mmmmmm.

You need to replace the two gaskets that are between the intake manifold/tstat housing and the head. These gaskets also sandwich a stainless plate that keeps water and engine gases ( in and out) apart.

Handy tool to have is a flat nose 6mm tap to "chase" (clean) out the threads in the block before putting it back together.

Thanks for the additional information. I'll keep you posted. This weekend I am tied up doing my ASA104 sailing certification, but I am anxious to get to the motor and see if it will be salvaged.

..
Norm

Thank you once again for the help. Here is where I am at. I opened up the thermostat housing and the plate behind it and found that the shop had damaged the gaskets when they took it apart, so before I did anything I ordered replacement gaskets (plus an extra set). I blocked the intake manifold openings and the exhaust manifold openings so I could scrape the old gasket material off, and so I could pour water in the water jacket without getting it in the cylinders. I found that the lower opening for the bypass was a little clogged, but other than that water flows freely between the top of the water jacket and the bottom, and air that is blown into one opening comes out the others, so there must be some circulation.

After reassembling everything I stuck the motor in a 50 gallon barrel full of water and started it up. Right after I started it water came out the telltales in a pretty good stream... but it only lasted for about 20 seconds and then started to get less and less until it stopped completely, after which it started to overheat so I shut it off. Half an hour later I started it up again. Once again I had a nice stream for about 20 seconds and then it petered out to nothing and overheated...

Is there a drive pin or something that could be sheared off on the impeller? Or is there something else I haven't thought of? The previous owner said he put a new impeller in it, and the shop that took the motor apart for me said that the impeller looked like new. I'm wondering if it was overheating on the previous owner and he tried replacing the impeller and then gave up and decided to stick me with it. The screen at the bottom is clear and the shop said that the tube coming up from the water pump was also clear. Maybe the shaft that drives the water pump has a shear pin that is sheared....

I still didn't get a shop manual. It's on my list for tonight.

Thanks so far.

..
Norm

Hi njwtech,
These don't use a drive key for the impeller. The impeller has a flat spot molded in that fits to the flat cut in the pinion (main) shaft.
A couple of things came to mind when I read your post about what could be happening. I'm not sure how this could happen but it sounds as if something is in the supply passage acting as a sort of valve. What I would want to do is to verify, absolutely, that the engine is actually overheating when the pee stream goes away. In other words, is the engine getting hot or do you THINK it's overheating because the pee stopped? If it's just the pee stream plugging then it is a simple case of trying to flush out whatever debris is in the water check pipe. But, if it is actually losing all flow, then it would be much more complicated.

Also, if the engine is indeed getting hot, there are a couple of places on the bottom of the oil case where there could be a bad seal and what might seem like a blockage or no flow from the pump could instead be a massive water leak into the extension case.

One of these seals is the one that holds the top of the water tube from the pump into the oil case. I've found these to be in VERY bad condition. I've also found the end of the internal passage that the water tube seal sits in can be badly corroded and deformed. Those I have cleaned and reshaped with epoxy metal filler so that the replacement seal has a reliable receptacle. In addition to the water tube seal, there is an Oring to seal the passage on the engine block side of the case. It is located inside the cross section of the oil sump gasket. It could leak but I think the upper water tube connection is the likely suspect.

To check these and repair them requires that the power head be removed. You sound as if you're comfortable working on the engine so I thought I'd tell you about that. If you get the Helm Inc. shop manual, you will see what I'm talking about.

Good luck.

Thanks, jgmo. Yes, it's definitely getting hot. The pee stream gets replaced by a steam stream. I don't keep running it after that so I don't damage the motor. Also, I removed the three individual tubes that connect to the pee outlet and none of the three has any flow.

I guess I have a project for tomorrow. This is so frustrating. I bought the boat a month ago thinking it looked almost ready to sail, and after a month of fixing stuff and working on it and spending money, I'm no closer to sailing. Oh, well...

Sometimes it's a good day boating if I can make it from my slip to the travel lift under my own power

So I found the answer. I don't know why I listened to those people that said the impeller was "like new". I didn't order an impeller when I was ordering all that other stuff. In spite of that huge bold warning in every manual stating to assemble it turning the right way to avoid damage, the previous owner assembled it with the vanes backwards. And then inexplicably the "outboard shop" I took it to assembled it with some facing backwards and some facing forwards. So as soon as it got any back pressure on it, the vanes facing the wrong way decided they didn't want to slide any more, so they stopped... but the shaft kept going. So the flat side of the shaft is now just a suggestion for the impeller. The impeller looks just fine, but the inside of the impeller where the shaft goes through is sloppy and can slip easily on the shaft now. I am going to see if I can machine something so I can use it while I wait for a new impeller, but it looks like another week is now lost. Thanks all for your helpful suggestions.

I had the exact same problem with a BF100 (same motor). The previous owner ran it in the great salt lake without flushing it. This is a dead sea so super saturated with salt. The only way I could get all the deposits out was to take all the covers off both sides of the motor and run wires through them until they were clean. The salt actually had eaten away some of the metal. I finally got it to pee water without plugging up again. I have a manual for the motor for sale on ebay right now for $14.99. Good luck!

I GOT IT!! I put a shim in the impeller between the flat side of the shaft and the impeller and it tightened up nicely. Then I reassembled everything, put it in a barrel of water about half way up the neck, and started it up and ran it for 3-4 minutes. Nothing. Not even a little. I figured I was screwed, but I tried one last thing before tearing it all down yet again. I put a garden hose on the intake with the flush adapter and forced water up into the pump. Then I started it up again and it started peeing more than I had ever seen before. I shut it down, removed the hose adapter, put it back in the barrel and away it went. Looks like I'm in business... I guess I had to prime the pump, even though it was in water about 8 inches above the pump... Oh, well. I'm off sailing this weekend. Thanks everyone for your help.

A couple of comments: First, you've got yourself a pretty sweet old outboard there. They are some of the best ever built.
Second, make sure you ground tackle is all it should be because even the best outboard won't get a sailor home EVERY time but your boat and sails will.

"Warping" into the slip is sometimes your only alternative.

Have fun out there!