2007 Honda 75 ignition problem - I thoink

Today my engine began running very rough with hesitation, lost rmps etc. I started checking ignition areas.
1. checked all plugs and they all looked the same & ok (and are only a few hours old.)
2. With engine running I disconnected 1 plug at a time expecting to see/ hear performance loss etc. - which I did for all cylinders except the very top cylinder. After 2 tests there was no decernable change in engine performance.
3. Attempting to eliminate 1 problem area I swapped plugs 1 & 2 and retested. No change in performance again in cylinder # 1 with # 2 plug in place. That eliminated a problem with the plugs I feel. That's where I'm at now and hope to get advice as to what I should check next. Oh yes I did try 1 other test. With the engine running +- 900 rpms I pulled out the engines manual choke which seems to smooth the engine out some but not a lot. Acceleration performance and lost rpms didn't change.

Thanks, any help will be appreciated. Calabashman

When you pull the spark plug wire off, and put it back on slowly, listening for the tick tick of the spark. If you hold it very close to the plug, you should hear the tick. If you do, you have spark.

Then go back to your choke test...only this time, remove the black plastic linkage that vertically runs between and connects all of the chokes. Then, with the motor running, reach up and manually rotate the #1 cylinder choke very slowly. You may not have to rotate it all the way. If the engine smooths out, it appears that at least your idle circuit in the #1 carburetor has a blockage. If you rotate the choke in an operating cylinder, it normally should cause the engine to bogg down.

That being said, it could be an incorrect setting of the idle mixture screw or even the carburetor could be way out of balance.

Sounds like a lot of maybe this, maybe that...but it could be any of those. If someone was tinkering with carburetor adjustments, it could be more adjustment problems vs dirty carburetor.

Trouble shooting is just eliminating the potential problems, so that you are left with the real problem....

In general, troubleshooting this type of problem you can just guess or ....do something like the following...

1. Check compression....make sure the cylinders and valves are doing what they should. A bad cylinder will not fire. If valves are out of adjustment, cylinders may not idle or function at all.
2. If compression is good....then check spark. You can use spark checker or at least a timing light or the spark ticking (explained above).
3. If spark is good...then do a cylinder drop test....like you did....isolating which cylinder is not firing.
4. Check the timing marks. One notch out of time can cause a situation that mimics a bad carburetor or cylinder.
5. If timing is ok, the cylinder that is not firing is out of adjustment or assoicated carburetor is clogged (as discussed above).
6. Check the adjustments....vacuum balancing requires gauges. Idle mixture screw, if it does not have a limit cap, may be turned in or out too far. The BF75 idle mixture screw should be set at 1 7/8 turns out (from lightly seated).
7. On the BF75 there is also a dashpot, check valve, that can cause some real problems if reversed (especially if someone else had their hands on the motor).
8. If you can choke the individual cylinder (as discussed above), that will give you more evidence. On many engines, you could shoot a quick shot of starting fluid into the carburator. If the engine picks up..then probably dirty carburetor. It is not possible to do on the BF75 without taking off the intake muffler. You choke method is probably going to be all you need there.
9. Once you determine that the carburetor needs cleaning, you can also run the engine at about 1500 to 2000 rpm and do another cylinder drop test. If all the cylinders are firing, then you know that you have to look closely at the idle circuit (which is usually the first to get clogged).

Many times, some of these steps can be bypassed and you can jump to a carb cleaning if they are your own carburetors. If a customer is going to pay, I like to eliminate all other possibilities before getting to an expensive carb job.

There.....I am done!

Mike

Calabashman said:

Today my engine began running very rough with hesitation, lost rmps etc. I started checking ignition areas.
1. checked all plugs and they all looked the same & ok (and are only a few hours old.)
2. With engine running I disconnected 1 plug at a time expecting to see/ hear performance loss etc. - which I did for all cylinders except the very top cylinder. After 2 tests there was no decernable change in engine performance.
3. Attempting to eliminate 1 problem area I swapped plugs 1 & 2 and retested. No change in performance again in cylinder # 1 with # 2 plug in place. That eliminated a problem with the plugs I feel. That's where I'm at now and hope to get advice as to what I should check next. Oh yes I did try 1 other test. With the engine running +- 900 rpms I pulled out the engines manual choke which seems to smooth the engine out some but not a lot. Acceleration performance and lost rpms didn't change.

Thanks, any help will be appreciated. Calabashman

Click to expand...

Hondadude, Calabashman here. 1st, Thanks for your reply. (Backgrouind) You probably don't remember but I'm the guy that you helped almost a year ago with my throttle cable adjustments AND my carb idle screw adjustments and carb cleaning. Since that time I've been ill a lot (74) and only had my boat out a few times. When we left my idle screw adjustments I installed new screws and was never able to get the engine to run properly @ 1-7/8 turns. I've have to run it @ close to 3 turns, where it runs the best - and it's been running good with just a little hesitation on acceleration. Since that time I'm only using Ethylene free gas to be safe etc. Yesterday before this happened I had been running the boat for almost 3 hrs, giving my guest a tour of the icw in NC - and it ran well until I was loading the boat onto the trailer. First sign of trouble.

Today I will start with the easiest areas to check. Yesterday when I removed the #1 wire I "thought" I could hear the tic-tic from the wire without it being close to the engine. I'll check again today. I have you reply and will begin @ day break. Thanks again, I'll keep you posted. Calabashman

Saturday am 9-7-2013
#1 test disconnected #1 spark plug wire and definitely heard & felt tic tic so it’s firing.
#2 (choke tests) – All chokes connected – 900rpm - no choke to full choke - no change
#3 All connected then disconnected -900rpm - no choke to full choke - no change
#4 All connected – 2,000rpms - open to fully closed – no change
#5 All disconnected – 2,000rpm individually opened to fully closed:
#1 – surged briefly then kinda returned to original rms +- when closed
#s 2 – 4 all decreased in rpms when closed
#6 #1 disconnected, 2-4 connected – 900rpm – open to full closed – no change
#7 #1 disconnected, 2-4 connected – 2,000rpm – open to fully closed – brief surge

That’s where I am currently. I’ll wait to hear back from you. Sounds to me like test #5 could be meaningful. Calabashman

Sounds like the idle circuit of #1 is clogged.

Before taking the carb off to clean....try this first....sometimes it works...sometimes it does not.

Take out your idle mixture screw and spring. Drain the #1 carburetor and take out the drain screw. Now take some brake clean or some carb cleaner with the straw on the nozzle and stick the straw into the idle mixture screw opening as far as you can. Give it several blasts. If you have compressed air available or even the can of compressed air (that you use to clean your computer)....gently blast (I know that is somewhat contradictory) air into the idle mixture screw hole. Repeat that process a couple of times.

I said to take out the drain screw so that the air pressure would pass out there and not blow something else apart inside the carburetor.

Put all the screws back as they should be, squeeze the fuel bulb to fill up all of the carbs and start the engine. Hopefully, that will clear the passage....but maybe not.

If not, you will have to remove the carb and clean, clean, clean.

Mike

First I want to thank you for the time your giving me. I really appreciate your help. I'll tackle the #1 carb screws/cleaning and hope it works. I've never removed a carb and I'm a little fearful of screwing something up, but let's see how this first step goes. Thanks again. Calabashman

Just purchased the brake cleaner as suggested. 1 question before I start. I'll take out the idle mix screw and the carb drain screw to drain the carb. Should I put the carb screw back in to retain the cleaner I squirt into the idle mix port or leave it out so it will drain? If I leave it in is there any danger of doing damage inside the carb if it's there for a few minutes? Thanks

BINGO - Just finished spraying the carb with brake parts cleaner/spray as you suggested followed by compressed air and a couple of squeezes of gas to be sure everything was clear and once the screws were back in place #1 carb ran perfectly, including loss of when I disconnected the plug. That did the trick. Not to wast an opportunity I also applied the same process to the other 3 carbs for good measure. I also tried to turn down the # of revs on the idel screws with no luck. Still need to run a 3 turns open. I was able to adjust the idle speed which went up to 1100+- down to 950 rpms. Can't wait to get it back in the water for a test run. Thank you again for your input, knowledge and time. You've been a great resource and we're pleased to have you out there. Calabashman

Glad things worked out.

The 3 turns out is odd....maybe someone stuck a set of 90 HP carbs on your engine. Those idle mixture screws are turned out 2 1/4 turns.

Hope all runs good on the test.

Mike

Health problems will determine when I test but I'm hoping they'll be good tests. Questions re: Carb removal.
Is it a complicated process to go through if I have to go there?
Do all/most outboard service centers use the ultrasonic carb cleaning the technique (assuming it's the best way to go)?
Ball park figure on cost to have someone remove, clean and reinstall 4 carbs?

Thanks again

There are a lot of pieces to the puzzle. If you have never done a carburetor before, it could be overwhelming. As I always recommend, if someone is doing this themselves, they should purchase the Honda Carburetor Manual. It have step by step instructions on disassembly and how to clean and what to look for along the way. http://www.helminc.com/helm/product...=&from=result&Style=helm&Sku=TM044&itemtype=N

As I said in a previous post, tonight, a thorough cleaning and vacuum balancing and water testing, replacing o rings, jet sets, etc could cost $800 - $900 or more. Most of the time, when the carbs are malfunctioning, they mess up the spark plugs and the oil. So they have to be changed too.

Honda recommends an ultrasonic cleaner, but it is up to each dealer to decide how they clean carburetors.

Mike