81' SEA Horse 70HP low end throttle kills motor. do I need new Carbs?

It runs waesome when at FT, but when attempting to start out or run at idle speed thru idle only zones it sputters and sometimes dies out. Especially when loading onto trailer it feels and sounds like it is being choked and does not have enough air and so it dies. It does become more difficult to re-start after this occurs too.
I use hi test gas, it runs 50:1 and i add an extra 1/2 oz for 5 gallons, I put SEA FOAM treatment on every other tank. Carbs look impecably clean on visual inspection and all floats and parts look to operate like they should.
Both filters (in-line) and the one on the motor are clean of any debris and clean overall.
being that other than this issue everything runs perfect I may just live with it, unless it will cause more problems for me later so pls advise if that may be the case.

What are my oprtions to remedy this problem?

Any and all suggestions are appreciated and welcome.

May all your fish be monsters and your days be safe

Thanks in advacnce.

-Reelfish

Re: 81' SEA Horse 70HP low end throttle kills motor. do I need new Carbs?

no easy ans to this just a lot more questions. do you have a tach and if so what is the rpm range you are having this problem at. have you ever compression tested the motor?. when was the last time the plugs were changed and what type are they. is the motor coming off a winter holiday. the carbs might be super clean but the rubbers seals might be super cracked or the float needle might be leaking by. if you like turning wrenchs carb rebuild kits are cheap so that and a link and sync might be all it needs.

Re: 81' SEA Horse 70HP low end throttle kills motor. do I need new Carbs?

Have you had the carbs off to check for internal cleanliness? Have you done a link-n-synch? Are the carbs updated with ethanol resistant kits? (easy to see - if the carb bowl gasket is black, it's old style. If it's orange or greenish, it's ethanol resistant).

Also, not necessary to run high-test gas. Will run perfectly well on 87 octane pump gas...

Re: 81' SEA Horse 70HP low end throttle kills motor. do I need new Carbs?

Hi Glen, Yes compresson test was same as the day it was built, No tach, no spedo.....PLugs & wires are new as of last week, dont plan to store motor as i live in Fl. and i do use a stabalizer if I know it will be sitting more than a month. I'm doubtful it is the gas if that might be something to check as I have run plenty thru it in the last 3 mo's. What is a LINK & SYNC?

As for the seals, have not checked, float needle have not checked either. Until last week I had no cover on the airbox (just purchased boat 3mo's ago)....problem existed prior to that though so yes...it might be dirty deep inside the carbs, does that sound like it may be something i need to do , huh.? or the bowls might be full of stuff too. I find this hard to believe as the owner has always used two filters on the gas line.
Question...why would it run great most of the time ( even after at FT for a minute then back to idle it runs fine then) but as the day goes on and the more I stop/fish/move. etc...it becomes more of an issue to run from idle, into gear, then to easy to get it going( sputter) and up to FT.
It's almost as if I were trying to jam it into FT the second it starts (and chokes out & dies) is the best way to characterize what is happening.

Looks like I iwill be tearing down the carbs huh....? Someone mentioned the old seal VS the new seals for the bowl on the carb that should be green/orange but if black need to be changed.

Love the name there Glen..lol and thanks for your help

Re: 81' SEA Horse 70HP low end throttle kills motor. do I need new Carbs?

your carbs have 2 jets one is high speed the other is low speed so its common for a motor to act up either at high or at low. a tach would help set your tick over speed in the water. chinewalker points out the color of the seals to help find what the problem was. if you open the carbs then you need to replace the seals as they realy are a one time use. the kits are $12-$20 a carb. in florida its common to get water build up in the base of the carbs and even under wot the water refuses to get sucked up so if the drain screws are a little messed up replace them at the same time. most people also advise that you change all fuel hoses at the same time.

Re: 81' SEA Horse 70HP low end throttle kills motor. do I need new Carbs?

Thanks Glen, Will do. All gas lines I also changed, i bet its the low end jet and the seals.....if not on to the next. what is LINK&SYNC?

Re: 81' SEA Horse 70HP low end throttle kills motor. do I need new Carbs?

link and sync is setting up the carbs so they all move together and at the right time this also affects the shifter look at the "top secret file" located at the top of the evinrude/johnson forum its full of real good advise