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BF45 carb sync question

S

Solamar

Member
First, what a great forum. Thank you Marine Engine for hosting this!

New to me 1993 13' Whaler with 1994 Honda BF45A LRTA (what is the difference between BF40 and BF45??).

First short trip out last weekend, would not idle, ran good at full throttle but would only reach 4200 RPM. Carburetors need cleaning (pilot jets will be replaced), float level checked and carbs synced (with Morgan Carb Tune). I have already changed plugs (looked fine), oil, fuel filter, gear oil and impeller.

I am a bit confused about the sync process regarding blocking off the vent tubes. I have the TMO44 service manual and it does not mention blocking vent tubes and I have a piece of a newer manual that calls for blocking the SE Tubes (vents?). My carbs have a metal vent rail with the dashpot, looks like in 2004 this was changed to a different configuration (SE Tubes). Should I block off the vent tubes?

Thanks,
Matt
 
I believe the SE tubes are for the "Starting Enrichment" circuits for the BYSTARTER fuel enrichment system for cold start. This replaced the "choke" on both electric start and pull start engines.

I'm not certain about blocking your vents for balancing but I'll check my carb manual to see if there is something there on the subject.

In the meantime I hope someone that actually knows can answer.

Good luck.
 
Last edited:
jgmo said:
I believe the SE tubes are for the "Starting Enrichment" circuits for the BYSTARTER fuel enrichment system for cold start. This replaced the "choke" on both electric start and pull start engines.

I'm not certain about blocking your vents for balancing but I'll check my carb manual to see if there is something there on the subject.

In the meantime I hope someone that actually knows can answer.

Good luck.
Click to expand...

OK, that makes sense. I'd guess the SE tubes are on the carb throat and could "cross contaminate" the vacuum measurements. I also think the normal vents are on the bowl and should not effect vacuum.

My jets are arriving later this week, should be a good Saturday project...
 
I don't think the SE circuit would cause a problem while syncing. If the engine is at proper operating temp (VERY important) and the bystarter is powered OR the SE cable is pushed all the way in, then the circuits should be effectively closed.

I couldn't find any reference to your vent tubes in the carb manual so I think I would simply install the manometer in the carb ports and try lining everything up. If it doesn't give you any trouble and you can dial the columns to match then that's success!

And....you can argue about a lot of things
But you just can't argue with SUCCESS!!

GOOD LUCK AND HAVE FUN!
 
jgmo said:
Just don't forgot to let us know how goes.
Good luck.
Click to expand...

Will do.

But, I think I already hit a snag...

I ordered my slow jet using BF40 parts list (no BF45 Parts list) it is referenced as "Jet Set #102" Must be a typo, #102 is not a jet set ??

I was just re-reading the TM044 carb manual and it says the BF45 requires slow jet (Jet Set) #42

So I call my parts house and give them my S/N, they say I need Jet Set #42A which they do not have, but they do have #42.

Wonder what I am going to get with jet set #102? Probably Jet Set #38.

Are the differences trivial? Should I try to source a #42A, buy a set of #42, or use the #38 that's arriving today?

Sorry, this part should be easy...
 
Yesterday I bought a set of #42 slow jets, they are stamped 42G (Honda P/N 16150-ZW4-000)
Today I received the slow jets from Boats.net, They are stamped 38B (Honda P/N 16150-ZV3-000)

Honda tells me that per my engine S/N I should be using slow jet 42A (Honda P/N 16150-ZV5-000)

I wonder what the suffix letter means?

Tonight, or maybe in the morning, I'll pull the carbs and see what main jet I have. If it's a #92 main I'll run the #38 slow jet. If it's a #125 main I'll run the #42 slow jet (per the TM044 Honda Carb Manual).

If nothing else, I have a plan...
 
I agree with Honda. Although I do not know your serial number, the BF45 only has one jet set and my parts program shows 16150-ZV5-000.

The 16150-ZW4-000 is for a BF50 and the 16150-ZV3-000 is for BF35's and BF40's.

I do not know how they differ....I only know, if I use the right part number, things work as they should.

The only wrench that might be thrown into this whole thing, is if someone, who may have owned the motor before you, chose to put BF40 or BF50 carbs on the 45.

The numbers on the carburetors should settle that thought.

Mike
 
I believe the part number confusion is a result of the seller telling me the motor is a 1994 BF40, but the s/n plate on the transom bracket had disintegrated. I gave Honda the engine S/N and they told me it is a BF45 (forgot to ask what year though). I didnt think to check Boats.net for a 1997, but sure enough, that is where the BF45 info is...

After disassembling the carbs, I found the Mains are #125 and the jet set is #42A. I had #42B jet sets and used them. The bottom carb had the mixture screw covered in RTV and sure enough was missing the o-ring and spring. Cleaning up the RTV to get a good o-ring seal was a pain, and I must have missed some because the first tune attempt the bottom carb would not respond to mixture adjustment. Pulled it apart again and spent a fair amount of time shooting carb cleaner through all the passages. Second attempt went great. That Morgan Manometer works wonderfully!

I was running the motor in a trashcan of water and monitoring cylinder head temp with a laser temp gauge, when the heads hit 210 I decided I was done (water temp in can was 110). Not completely confident I got the mixture perfect, had to screw in at least one full turn before RPM.s dropped, then backed out about 1/4 turn to recover. It was pretty incredible how a rough Idle smoothed right out with just a slight balance adjustment, definitely makes a huge difference to balance the carbs...

Then the bad news, had to get towed in by the dock master. Seems my charging circuit is not doing it's job... I'll start a new thread with questions.

Huge thank you for your help!

Matt
 
Good that you're having success.

Just one more thing to conquer and then maybe you can just enjoy boating for a while.
 
jgmo said:
Good that you're having success.

Just one more thing to conquer and then maybe you can just enjoy boating for a while.
Click to expand...
I seldom admit it, but I kinda enjoy the challenge of getting a problem like this sorted... Especially with you all coaching me through the rough patches!

I should have mentioned. Saturday on the lake (before the battery died) the boat was running beautifully, silly fast, jumps up onto a plane in the amount of time it takes me to push the lever forward. Smiles all around, WOT about 6000 RPM, (the PO had set the tach at 4 pulses, should have been at 3). Let my 12yo son drive it for a bit, then the battery died. Drifted to a rocky point and talked about Baer Grills survival tips while waiting for a boat to pass, not a bad way to spend a day!
 
hondadude said:
That 45 should make that little 13 footer move. Check p 47 of the owner's manual. http://cdn.powerequipment.honda.com/marine/pdf/manuals/31ZV3601.pdf With the key switch turned to on, you can pull start the motor without the battery....as long as you have some sort of rope to wrap around the flywheel. So you do not have to worry about eating lizards or ants to survive...although, they are a good source of protein.

Mike
Click to expand...

A 10mm socket and some rope will definitely become permanent residents on the boat! That and I'm adding a dash voltage gauge:cool:
 
Quick update. I added the #42A jetsets to my rectifier order, Installed last night and it idles considerably smoother and lower. Wonder what the difference was...
 
These carburetors are pretty precicely engineered to deliver fuel as efficiently and effectively to the engine they are prescribed for. Many considerations I'm sure most of us are unaware of like volumetric and thermal fuel requirements over a range of operational conditions dictate how they are cast, drilled and jetted. To understand what they did we would all need to take a few engineering courses.......and pass!

Even then I'm not sure I could "get it".

Basically though, to achieve their desired results they drilled air passages to move a certain amount of air through the body to create a certain amount of "lift" to pull a metered quantity of fuel up, through and out the the CORRECT jet set. If you compare the one that just "works ok" with the jet set that works great, you will likely find small but measurable discrepancies.
That's why most of us just try and get the right one instead of something that just works.
 
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