Help honda 90

Hi All,

I use my twin engine Boat to make my living and I need your professional help Hondadude / Master Techs! This is my busy season and my 1997 Honda BF90 failed me today.

I was cruising along in horrible conditions and the boat felt like it lost power and the waves had more control of me than I had on them. Long story short, my starboard 1997 carb Honda BF90 lost power. It struggles to get to 4k RPM and getting on plane takes forever. I have to push the throttle lever almost wide open to keep 4k. 4200 RPM is max wide open now. The fuel flow meter usually says 3.9 to 4.4 GPH and it's now it's in the mid to high fives. The motor is drink tons of gas to keep 4k RPMs and will fall if you hit a wave or....

I'm good with outboards and have a parts engine and Honda factory service manual. I just walked in and I'll start reading now but I must work tomorrow......with the boat!

-Hanging over the stern I dumped the fuel from each carb.
-Pulled each spark plug wire and heard "zapping sounds" from each. Certain cylinders caused the engine to stumble more then the rest.
-I chocked the bad motor when at 4k and the motor didn't like that. RPMs dropped for a second or two.

The engine starts fine. Idles fine. Doesn't shake. Doesn't pop, studder or.......

When I was flushing the motors at the ramp the bad motor's T stat housing and head felt hotter to the touch. No overheat alarm and pisses great. I installed new water pumps last year. The dash lights show green, all is well.

I have new (last year) fuel filters in the engine and racors before the engines.

What do you think? Thanks!

The Honda trouble shooting says
"Engine speed does ot increase"
1. Choke not returning. (Checked that. is OK.)
2. Throttle cable misadjusted. (Will check tomorrow. )
3. Propeller Mismatch. (Not my problem. Had them for years.)
4. Overheat, engine oil pressure alert system functions. I(I had no alarm but I may pull thermostat out and run it like that for one day.)
5. Faulty spark plugs. (will change tomorrow.)
6. Clogged fuel filter. (Will put my old one back on from last year. Will drain racors tomorrow too)
7. Water in carb. (drained but will drain again now that I'm back on land.)
8. Incorrect valve timing. .....(gonna skip this )

I should do a compression check too.

Definitely check the things out on your list....

A couple of additional things to check....only based on low rpm and excess fuel....it sounds like you lost one cylinder.

While on land, run the engine and do a cylinder drop test. You said you had ticking with each plug wire pulled...did each cylinder cause a decrease in rpm? If it doesn't....that is the problem cylinder

If you have a compression gauge....take the compression of all the cylinders to make sure there is not something wrong in the cylinders.

Squeeze the fuel bulb and see if it ever gets hard. Check your carburetors for any overflow. You may have a float stuck open. Also, check the spark plugs to see if any of them look a lot blacker or a lot cleaner than the others.

One last thing comes to mind....one of your fuel pumps may be failing or may be leaking into its driven cylinder. You have to take each one off (leaving the fuel lines connected) and squeeze the fuel bulb and check for leaks. If one leaks, replace it.

Those are the most likely places that I can think of that will cause excess fuel usage.

Mike

I'm on it as soon as the sun comes up! Thanks!

I just got my rain coat on and tested the below two points.

Yes. The primer bulb does get rock hard.
Yes, every cylider is working. I pulled one plug wire off at a time and each one causes the engine to drop in RPM and shake. Every cylinder is 100% firing.

Usually Honda electronics are strong, so with each of the cylinders firing I think I can rule out electrical. The coil packs were replaced last year as a maintenance item. I haven't done anything to motor this year so I didn't just monkey with anything.

What's next?

I'll work on my above list now and check fuel pump. I'm taking one off of a parts motor to review it.

If you do all the basics we have discussed and checked compression....since you are looking over everything...... you might check to see what the gearlube looks like. If for some reason, you blew a seal and it has let water in, the non lubricated gears may be giving you extra drag.

Mike

Thanks Mike!

I just noticed my volt meter drops to 12 volts when on plane and then sometimes climbs to 14 when idling. Strange. Still have my issue with power/speed, I'll check the charging circuit.

You may be on to something there. Check the battery and its connections too. The CDI unit takes the 12v and converts it to a much higher voltage that goes to the coils to make the spark. If the voltage to the unit goes down, the output may be going down also.

If the charging system is not causing your running problem, one other last resort.....since you have a parts motor is to change the CDI unit. It is very unusual for these to fail, but I have come across one that through all tests seemed to be a carburetor issue, but the problem persisted after the carbs were cleaned. It only failed at full throttle like loosing a cylinder...changing the cdi unit fixed the problem.

Mike

I'm on it! Thanks Mike!

If the Fluke volt meter shows no charging I would install a new stator and test again. I wouldn't touch the CDI until I'm charging and I still have the power problem. You agree?

My factory Honda service manual shows how to test all the electrical gear. Great book, just sucks having to use it.

Yes. Get the charging system working correctly first.

I would not jump at changing the stator....you also have a regulator/rectifier and a bunch of connections in the circuit too. Besides....the reg/rect is much easier to change than the stator.

Unfortunately, I don't think there are many tests other than resistance for the stator and the reg/rect.

I would also check the current output if you have a clamp on attachment for your fluke.

Mike

I'm on it. Thanks!

Yes, resistance for sure.

I think I may have found my issue.

My stb motor battery had a very loose ground cable at the top of the battery. I could move the three grounds around by pushing it with some force. It was by no means nut off and cables only on by gravity.

Would a loose ground blow anything that I should now test/replace? Regulator?

Re:MORE Help honda 90

I still can't solve this. My 1997 Honda 90HP has not much power and won't go over 4400

I found loose grounds on the battery post. Tightened.
Two new fuel pumps. $154
New spark plugs. The right NGK
Dumped the gas in the carb and the racors. looked clean.
I tested the charging system and it is charging fine. 14.5 volts each motor. I tested it 5 times today,
I shot each motors thermostat housing with the gun and both were 158 degrees.
I connected the ole fashion timing light to the bad engine and every cylinder blinked the light evenly.

I was on the water for 9 hours today. Started, ran idled great. Never missed a beat. No sputter no nothing. Just no power and it won't go over 4400 RPMS. It used to do 5500 PRMS,

What else? I still have to do compression. Could it be timing? I never messed with anything.

I can swap out the computer I guess.

Yes, definitely check compression and check the timing marks.

Also, verify that when the shifter is at full throttle, the carburetors are wide open.

Mike

I'm on it! Thanks Mike.

had this kind of problem before - mine was a series of small things causing the issue - slightly dirty carbs, but mostly slightly burnt valves - a compression test and then leak down test solved the problem

Thanks Jake, I'm heading in that direction soon.

Full throttle test:
Without running the motors I put both shifters in the full throttle position, all the way forward as far as they could go. I pulled both motor covers off and looked at the Throttle opener cam located under the bottom cab. to see where the throttle cam roller was inside of the cam. Both motors looked exactly the same.......not in the full throttle range. (I'm using page 3-11 and 3-13 of the honda book to write this.)

My cam rollers stopped just at the point where the cut out in the throttle opener cam makes a sharp turn. I'm 95% open but technically I'm not to spec. Neither motors are to spec.

I do not think this is my issue but I will follow the adjustment procedure at one point.

Finding a second person to help with compression has been an issue. That's next and needs doing asap!

I'll check the manual for leak down data, PSI and time. Hopefully I can do that using my gear case pressure tester!

COMPRESSION TEST: 175 per cylinder. Looks good.
GEAR CASE oil was perfect. No water no metal.

I'm just about stumped. All that's left is installing my spare ECU and gear case and maybe run it off a 6 gallon dingy tank. Timing too.

What am I missing????????

The day it lost power was in a 35 knot storm. I ran from harbor to harbor on plane and worked in the calm water. When I was running with the big waves on plane I remember hitting a huge wave then no power. At this time the waves had me and I could not keep boat on plane. I had to turn around into the waves and go home slow. It was so rough that this slow speed had the outboards, on a bracket, dunking underwater the entire trip home. When I got back to the harbor this bad motor had 2-3 gallons of salt water in the cowl. I always assumed this water came in AFTER my power issue. Maybe I'm wrong. Maybe it's part of my issue. Oil level is fine. I didn't pull the started to see if water got past it. Starter did have a new rubber gasket under it and was clean last year when removed.

Electrical connections on the motor? Salt water does wacky things to electrical connections.

Water in the flywheel area, normally, should not hinder rpms...but who knows?

Check your intake for any debris or broken screen. The screen in the silencer on the older 90's have been know to break apart and sometimes lodge in the carburetors....although, it typically causes a bad idle, it could do other things.

You might also disconnect the wire attached to the temperature switch and see if that makes any difference....could be a partially closed switch that is confusing the ECM.

Definitely check the timing. Also, run it off the dingy tank.

The compression seems a little low, but all cylinders are the same. specs say 213 plus/minus 14. Slow cranking could be the cause of this or throttle not opened all the way.

I am stretching to come up with anything else....other than carburetors or internally collapsing fuel line between the fuel tank and the carburetors. So it could be on the in the boat or in the engine.

One more thing, try pulling the manual choke on the engine a slight amount and see it that helps. If it does, then it is probably in the carburetors.

Mike

Ok, I'm on it! Thanks!