Motor bogs down when going to full throttle

[nmscuba]

Ok, restoration project here. 1997 Honda 75 hp 4 stroke. So far I installed a new water pump, spark plugs, fuel filter, oil filter, engine and gearcase oil. I tore down the carbs and cleaned them all, new gaskets everything. Installed new fuel lines on engine and also new fuel lines from 6 gallon tanks to engine with new bulb. I cleaned both tanks, took apart the caps and floats. When i pump up the bulb its firm, no gas leaks anywhere.

I used a inline fuel pump pressure gauge tester, 2 pounds on all feed lines and when bulb is pumped firm its 10lbs with no leaks any where

I have also adjusted the vacuum diaphram accelerator and synced the carbs.

So heres my problem. Its idles great, when put in gear and slowly advancing throttle it runs great, but if I go from in gear to full throttle it dies I have to go slow to about 2000 rpm doing that or it dies from 2000 up you can slam it and its great.

Also when it sits for say an hour or so while were fishing the bulb loses prime and I have to pump it firm again.

Do anyone have any ideas cause im all out??

 

[pvanv]

Re: Motor bogs down when going to full throttle

Sounds like the transition circuit is a little lean. Try soaking the carbs in carb dip again.

The check valves in the bulb may weep a little... not uncommon to "lose prime" after a while. Might not be a malfunction. Remember that the bulb is under suction when the motor is running, so it may well not be hard, but it should not collapse from too much vacuum. If there is a leaky o-ring at the fuel line connector -- either at the tank or at the motor -- some air could get in the line, and cause the bulb to be soft as well.

 

[nmscuba]

Re: Motor bogs down when going to full throttle

Sounds like the transition circuit is a little lean. Try soaking the carbs in carb dip again.

The check valves in the bulb may weep a little... not uncommon to "lose prime" after a while. Might not be a malfunction. Remember that the bulb is under suction when the motor is running, so it may well not be hard, but it should not collapse from too much vacuum. If there is a leaky o-ring at the fuel line connector -- either at the tank or at the motor -- some air could get in the line, and cause the bulb to be soft as well.

What is the transition circuit?? Man I did not want to have to tear the carbs down again LOL it was easy but the linkage was a pain getting back together.

I have not changed fuel line connector on the motor only the hose to the tank along with the bulb so maybe I will try that since its original one still and see.

But I need to know what that transition circuit is?

 

[pvanv]

Re: Motor bogs down when going to full throttle

As you transition, or "tip in" from idle, the mixture needs to be substantially richer to avoid fuel drop-out and bogging. That section of the carb is referred to as the transition circuit.

 

[nmscuba]

Re: Motor bogs down when going to full throttle

As you transition, or "tip in" from idle, the mixture needs to be substantially richer to avoid fuel drop-out and bogging. That section of the carb is referred to as the transition circuit.

Ok now I understand. But my question is if I tore down the carbs, made sure each jet was clear, torn down all the brass center tube andmade sure that was clear, what could be plugged and where?

Could this just be an adjustment to richen the fuel or the pilot screw not properly adjusted?

 

[Sea Rider]

Re: Motor bogs down when going to full throttle

If carbs are inmaculate clean, no air entering through hose tank/engine connectors and still keeps on bogging. Being a 16 year oldie, you might have a leaking head gasket condition. Could have a dried, burned, out of torke gasket which is not sealling tight allowing cooling water to get inside combustion chambers and engine bogging down, specially at wot.

Happy Boating

 

[nmscuba]

Re: Motor bogs down when going to full throttle

Hi,

No I did not soak the carbs in carb dip cause the manual said not to as it would remove the paint from the carbs. Honda recommends an ultrasonic cleaner using water.

I did get the Honda Carb Manual and I went though that whole thing step by step as it instructed. That was priceless and I learned so much from that. My dealer actually gave me a free PDF copy of it.

All jets and transitions seem to be pushing out carb cleaner per the manual and I ordered a jet cleaner set of wires so I can run them though just to make sure.

I did find my number 4 carb on the bottom the slow speed jet was plugged so im hoping that was the problem but won't know till my gasket set comes this week to put it all back together..

So just to cover my butt I will give my carbs a soak in carb dip just to make sure.

Thank you PVANV

 

[nmscuba]

Re: Motor bogs down when going to full throttle

As you transition, or "tip in" from idle, the mixture needs to be substantially richer to avoid fuel drop-out and bogging. That section of the carb is referred to as the transition circuit.

I want to thank all of you for your great info. I completed my second tear down of the carbs using the Honda carb manual, got it all together yesterday and synced the carbs too per the manual.

I took her out on the lake and OMG she runs awesome, No more bogging down and a smooth transition and what a great idle now too.

I still do have a slight hesitation like less than 1 second long but from what I read in the Honda carb manual there is a updated dashpot solenoid for my 97, Mine is grey and black and the udated one is brown and black and its suppose to get rid of that slight hesitation so thats on order.

Once I get that I will report back on how it works. But again thank you

 

[sgmacking]

Re: Motor bogs down when going to full throttle

I want to thank all of you for your great info. I completed my second tear down of the carbs using the Honda carb manual, got it all together yesterday and synced the carbs too per the manual.

I took her out on the lake and OMG she runs awesome, No more bogging down and a smooth transition and what a great idle now too.

I still do have a slight hesitation like less than 1 second long but from what I read in the Honda carb manual there is a updated dashpot solenoid for my 97, Mine is grey and black and the udated one is brown and black and its suppose to get rid of that slight hesitation so thats on order.

Once I get that I will report back on how it works. But again thank you

Glad you got everything working well. I am about to tear apart the carbs on my 2003 b75a and wanted to know which vacuum gauge you used to sync the carbs. I've found them online from $60 - $353.

Was thinking about this kit: New Vacuum Carburetor Synchronizer Carb Sync Gauge GL 1100 1200 1500 Honda CB | eBay

Also, any tips on the process? Never cleaned the carbs on this outboard before, so any help would be appreciated. Would you be able to forward that PDF to me?

-S

 

[nmscuba]

Re: Motor bogs down when going to full throttle

Yep those are the ones I bought. Click the make an offer. I tried $55 but was declined but he accepted $60. They worked great and the dampeners stop the needle bounce so it makes it easy to calibrate

Do you have the Honda Carb Manual? That has a wealth of info in it.