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BF25A is very hard to pull start now.

Atempt

New member
BF25A with a serial number BAJS-10015XX

I got this motor used 7-8 years ago. It ran fine when I got it and I could pull start it easily with one hand while sitting in the back of the 16' tin boat.

It then sat in a barn enduring temperature extremes for 7 years with the occasional use from family. Different people have "worked" on it so I don't know exactly what was done. I took it out a few weeks ago and found the pull start is now a two handed job with a foot on the transom. We got it running but noticed the water stream out the back wasn't working, and the oil light stopped flickering. I took the lower unit off with help from posts here and found the water pump had eaten itself. I have the rebuild kit for that.

I have now tried to pull start it with the lower unit off and it is still incredibly hard to pull. I took the recoil rope assembly piece off. Manually turning the flywheel underneath is difficult. I put the pull start piece back on and took the spark plugs out. It was then super easy to pull. I also tried it with a spark plug in only one cylinder. It feels like each cylinder has equal compression. It makes me think there is too much compression now? Or there is a decompression valve that is stuck close? I ordered the Honda parts manual, but I'm hoping someone smarter has some ideas?

Also, I'm not in great shape, but I'm 6'1, 200+ lbs and under 40yrs old. I should be able to pull start this thing.
 
Yes, you should be able to pull that engine over easily and no, there is no "decompression" device to stick closed.

My fear is, from what you've described, is that the engine may have overheated at some point and has been damaged as a result. The oil light flickering could be from a very low idle not turning the pump fast enough. But if is idling slowly due to drag from friction caused by the metal deformation that takes place with overheating then that is not good.

While engine compression does go up due to carbon build up from poor combustion, I don't know that it would effect the way the engine turns all that much. But, doing a compression test is never a bad idea if done correctly. It can yield good info that you can use for evaluation.

You should probably check the oil pressure before trying run the engine any more. It's pretty simple to rig a gauge and screw it into the oil pressure switch hole. You can then pull the engine over with the plugs removed to spin the pump fast enough for a reliable check.

I'm hoping that you ordered a service manual and not the parts manual because I'm thinking that you're probably going to need that to get this outboard back "up to snuff".
 
So it turns out I did order the service manual. I followed the cylinder compression instructions on pg. 2-15. Cylinder compression on the specs page is 128+-14 psi. My engine compression is below. It is the highest I could get while using the pull start.
Top cylinder: 117psi
Mid cylinder: 102psi
Bot cylinder: 105psi

I also tested the oil pressure following instructions on pg.2-26 after replacing the water pump. The specs page say it should be above 15.6psi. My engine started at 59 psi, then fell to 50psi as it warmed up.

It is still entirely too hard to pull start, and the service manual doesn't really address this problem. I'm planning on changing the oil and opening up the cylinder head cover.
 
Well, a couple of things that are of interest to me. First is the compression test results are what could be considered "marginal". The reason is that it's generally considered a failed test if any one cylinder isn't within 10% of another. Your engine falls outside of that in that cylinder one and cylinder two are 12% apart.

But, that's not something to get discouraged about until you do pull the valve cover and check valve lash.

The oil pressure specification of 15.6 psi is the minimum at hot idle I would think. I am surprised that you measured almost 60 psi. I'm guessing that is at a much higher rpm than idle, correct?

You are pulling the engine over while in neutral aren't you? I mean it's strange that you're having so much difficulty with that.

Just trying to come up with ideas...no insult intended.
 
I took the cylinder head cover off and checked the play in the rocker arms at the top of each stroke for each cylinder and they were identical as far as I could tell.

The oil pressure didn't move alot due to rpm. The lowest oil pressure I could get was 50psi right before the engine died due to idling too slow. I have a hard time keeping the engine running. I think it's not getting gas due to a problem with the gas line. Someone rigged in a shutoff valve and the clip into the engine doesn't look like the Honda one in the picture. I will be replacing that next I think.

I think the engine is in neutral. I notice that when I very slowly pull the recoil rope the prop spins slightly, once I pull it a little harder it will stop. Also when it's running in neutral the prop spins at 5-10 rpm, it's not fast. I think the next step is to take it to an actual mechanic. The only other idea I have is to convert it to an electric start if that is possible/feasible?
 
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Atempt,

I imagine, with enough money, parts and time, you could convert this to electric start but I wouldn't try if it were me and I was having the sort of issues with the engine that you are now.

I'm a bit lost as to what is causing the engine to be so difficult to turn. I am also suspicious about 50psi oil pressure at idle. I consider that as being unusual, especially for a worn outboard. Not knowing what you've got for testing, it makes me wonder about the gauge you're using. I would be interested to know what the pressure is after the oil and filter has been changed. Is the oil light still not coming on? You do know that the green oil light is supposed to be on when the engine is running don't you? I only ask because many people aren't aware of this "uniquely Honda" operating condition.

Simply comparing the valve lash of cylinders to one another is no substitute for doing a proper check and/or adjustment of each valve.

I do sympathize with you about other people "tinkering" and possibly installing incompatible parts. It makes me wonder what else may have been done besides the fuel connection.

It does sound as if the transmission is in neutral when you're pulling it over and, after going back and re-reading what's been written, it was difficult to turn with the gear case removed.

I still suspect that the engine may have been overheated at some point but that is just a guess from a very, very, long way from "the scene".

I would agree with taking it to a reputable mechanic and having it evaluated before doing anything "expensive" in order to make it useable for you.

Good luck.
 
Just an update:
I took it into the recommended boat mechanic in my neck of the woods. He is not a Honda dealer though, he just works on all types of boat motors if that matters. I talked to him twice. First time he told me 25hp 4strokes shouldn't be pull started, too big of an engine. I told him to look on youtube to find people easily starting this very engine. He said he would look at the engine again. A few days later I went in to pick the boat up due to not wanting snow in it while sitting in his yard. He came out and said the lower cylinder had low compression 40psi, and he showed me rust inside one of cylinders on a picture in his phone. He also said it was too hard to pull start with the plugs out. Doing a rebuild on the motor was the only suggestion he gave me, but wouldn't give me a price, or any suggestions on what to try next. I had the feeling he was glad to get rid of it. I don't have much confidence in any of this besides he didn't know what was wrong. He also suggested putting an electric start on it though, but the parts lady at the shop said she couldn't find one for that motor.

I don't believe the low compression, and I have a scope to verify the rust. I don't know what to do after that. I have the shop manual, I might just start taking it apart this winter. I would feel bad selling it as a working engine, and don't see much of a market for a parts engine.
 
Rust in that cylinder indicates water intrusion. Such as may happen from a blown head gasketl.
From the beginning of your post I've felt that this engine was likely overheated and damage has been done.

Since it sounds like you really don't have a GOOD place to take it to and you have the shop manual, you may end up being the best help you've got.

If you have some ability and some skill at close tolerance measuring, it does make sense that you tear it down and do a proper assessment.

But doing your own compression test and leakdown test should be your first steps before disassembly.

Good luck.
 
i just saw this and i own a 25hp honda tiller 2004, i brought to a mechanic to do a tune up after year two, he in formed me that my outboard was an "anchor" i might as well junk it, no compression in one cylinder. i told him not to touch it anymore and picked it up and brought it to a hond outfit. the mechanic told me that on starting one cylider would not have compression to facilitate an easier pull start. if all were on it would be very hard to pull. i don't know if this is true or it helps, but my motor runs like a top to this day.
 
Update 2: Thought I would continue documenting this here for the next poor guy that has this problem.

After ordering a 46mm wrench and flywheel puller... I took the recoil starting assembly off. There is a flywheel on top of the crankshaft that controls the pistons. There is a timing belt that connects to a cam pulley that connects to the camshaft that controls the valves. With the timing belt in place, the two shafts are connected and it is hard to turn by hand. Once I had the timing belt off, each shaft was significantly easier to turn. This doesn't make sense to me, unless the circumferential force of the timing belt is causing binding due to a bad bearing? Without the timing belt the sideways force isn't there and shaft can more easily ride in the center and not bind? No idea on this one.

Anyways, I kept going and have the cylinder head assembly off. The suggestion from JGMO about blown head gasket was likely right I think. 4 head bolts were "easy" to remove. 2 bolts next to the center cylinder were way more difficult to remove and covered in rust when I got them out. I marked their location in the pictures below with a red circle. Any comments about cylinder condition?
https://imgur.com/a/Qq2GeHh

Next I think I will pull/take apart the cylinder block. I'm starting to worry there won't be something obviously wrong and JGMO is right again with the necessity for close tolerance measurements.
 
Well, I'm not seeing any obvious sign of water intrusion of the cylinders. Hard to say from here. Typically water would cause a sort of "steam cleaning" effect with a whitish appearance of affected cylinders, especially the combustion chamber.

I think you could have a point about the timing belt causing shaft deflection. Another possibility for the engine being "stiff" might be binding or bent valve stems or even crankshaft thrust bearing wear. You may want to check the oil pump while you're in this far. They usually just get looser as they wear but you never know. Also, I seem to remember you listed very high oil pressure so that might be a stuck regulator.

The bolts you had trouble with are on the exhaust side and are middle and upper so they would be subject to more heat than most of the others.

I don't know if it's a trick of the photo but the middle piston looks to have some damage at the bottom and right side of the edge of the crown.(?)

The bottom cylinder seems to possibly have lost a bit of oil control as it looks to have more carbon buildup than the other two.

These are just quick observations from the pictures and things may not be as I see them. Lots of ifs and maybes
 
Looking at camshaft runout: If I measure runout on the cam journal as the tech manual instructs I'm within the .001 in tolerance. If I move the runout gauge over to a the area in the picture the gauge varies from 0 to .03 inches.
https://imgur.com/a/ZLyCyE0

I can physically see the high side when turning the shaft. Is this a problem? or common for a camshaft off of the cam journals?

Next question is do I just replace the camshaft from Honda for $277. Or should I replace additional parts since I'm this far in already and this failure likely caused other problems? Or would I be better off buying a whole new cylinder head assembly used off of ebay?

I don't see any bent valve stems, they all look straight when I spin them in a drill. I have replacement thrust washers and all new bearings for the crankshaft and bearings for the connecting rods. I'll likely get new piston rings also just because I'm already this far into it.
 
The area you've mounted the indicator stem on is an unmachined part of the shaft and won't provide any useful measurements. A lot of the 0.028" reading seen on the gauge is probably due to the roughness of the surface.

Mount your indicator to the cam bearing journal as is depicted in the illustration from the service manual. If runout is within limits and the journals aren't worn there's no need to replace the camshaft.

You can roll the valve stems on a flat piece of glass to get an idea if any are bent.

You should probably spend some time measuring the cylinder bores and pistons.
You will want to know if either pistons or cylinder bores are out of round and if either of the bores is tapered.

If replacing the rings you should run a glaze buster in each cylinder so that the new rings will seat properly. That is, of course, if the block isn't too worn.

I would also do the inspection of the oil pump as described in the manual. Remember, you're looking for the reason this engine became so difficult to pull over and get running.

There are several replacement bearing shells listed so accurate measurement of the main, rod and cam journals should be done to match the replacements. I also recommend the use of Plasti-Gage to verify proper oil clearance is achieved before engine reassembly.

Check piston pins for galling as that could account for excessive friction.

I mean, there's a fairly long list of checks and measurements if you want to get reliable results after she's all back together. It looks a bit overwhelming at first but as you work through and check off each item, the finish comes into view fairly quickly as it is a relatively small engine. Let your service manual be your guide and you should be rewarded with an easy to start, reliable outboard.

Good luck.
 
Final update hopefully; just updating if some other poor soul has the same problem.

I replaced every bearing (bushing), thrust washers, oil seals, piston rings, thermostat assy, used a glaze buster, lapped the valves, cleaned out the valve guides with the special tool, replaced all the cylinder springs, and changed out every gasket. I bought all the gear to measure tolerances but couldn't find anything obviously wrong. I put the engine back together and it had the exact same problem. I'm probably in at least 500$ at this point.

So I then bought a powerhead on ebay for a BF30 for 850$ that was involved in a car wreck. Once this showed up I could tell the crankshaft on my original powerhead was the problem. I was surprised how easy the crankshaft on the new powerhead is to turn. I put my carbs, oil pump, fuel pump, electronics on the car wrecked powerhead and installed everything. It now works and I can start my motor much easier.

When I was taking apart the engine originally I found small pieces of rubber in the oil pan and rubber packed into the thermostat assembly spring. I think those pieces of rubber kept the thermostat from opening and caused my engine to overheat if that is possible. My biggest problem was a complete lack of reference on what is normal so it was difficult to tell what the problem was. Going forward I'm going to replace the thermostat assy spring and water pump every year. If I had to do it again I would tear apart the powerhead looking for obviously broken parts but not finding that I would buy a used powerhead instead of doing all the tolerance checking. Jgmo, I'll send you some booze for all your help and celebrating I can go fishing again. Thanks
 
Wow! I can't believe you're tenaciousness! You do NOT quit! It's GREAT news you got this baby goin' again!
You can give classes on the 25A now!
Goodonya Atempt and thanks for the success story.

JimmyD.
 
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