only 3800 RPM at WOT - loss of power under load -- please HELP

[reeldutch]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

when you are at wot you got to push in the key to activate the primer.
it has noting to do with the primerbulp.
when pushing in the key you will richen up the fuel/air mixture.squirting extra fuel into the intake manifold.
if it picks up for a short moment that means that you are running to lean.
if it bogs down even more, than your mixture should be about right.

check that out.
your idle rpm is fine.
if your fuel system is good meaning no air leaks
as you sound confident you dont have but did not verify it, and your fuel pump has good fuel pressure and your carbs are clean, you got to do the spark check with the timing light at wot.
see if the spark cuts out or may be you do have spark.

if you dont have spark we will have to troubleshoot the ignition system.

if you do have spark make shure your link and sync are correct and that your timing is set correctly.

 

[jrousell]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

reekducth - I cannot say this enough -- I really am very thankful for your time and expertise!!!


I hope I can repay the kindness sometime to somebody.

Anybody ever need web design/development advice/questions- let me know.. Maybe I can return the favor somehow...

I will try those checks today ( weather permitting) and post what I find.

 

[reeldutch]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

no problem at all.

hope we will get this thing running up to 5500 rpm.
just stick around the forum and we will figure it out.

it harder to diagnose online then when i can see and hear it myself.

what we found out so far is that :
- compresion is good
- you have good spark at idle
- idle rpm is good

basicly you need 4 things to run the motor.

compresion
spark
gas
timing

here are some possible problems:

- dropping cylinder
- timing not advancing
- dirty main jet
- airleak/ fuel restriction

dont rule anything out yet.

 

[iwombat]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

Just something to check . . .

I had this happen to me and it took forever to figure out, but same symptoms. I had a loose float bowl drain plug. I'd get a drop or two of gas out, but it never really pooled up, so I didn't see it. It was sure sucking up air though. Just a real quickie to check while you're hunting around with the rest of the list of things to check.

 

[ezeke]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

Thanks JB

 

[jrousell]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

OK so here is what I found...

using timing light while driving all 4 spark plug wires were getting lit all through the rpm range.

At idle the #1 plug was clsoe to 4 degrees off TDC and at WOT it was somethign like 25 or 26 degrees I think

How does this sound?

If this information helps ---> With me hanging of fthe back the boat wouldn't get up on plane, and therefore would only get up to 3000 rpms - not to the 3800 that it will once we get it up on plane...


It must have been a sight for people on their docs to see my fat arse hanging off the tail end of the boat with the cowling off while my brother-in law was pushing the throttle down....

 

[reeldutch]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

that sound like there is no ignition problem at all.
thats good news.

so now we eliminated compression and ignition problems.

next what you should check out is the link and synq.
did you hit the primer to see if it would pick up?

we are defently getting closer.
and the problem you have looks cheaper and cheaper.

you dont have a a bilge full of water or extra barnacles grown on the hull?
right?


now the only problem left is fuel.

this is what i would do.

take the air silencer off. plastic cover in front of the carbs.
with motor not running push the trothle lever to wot.
check the trothle plates inside the carb they have to be vertical.

if thats good than there shoulkd not be any reason exept for fuel delivery that you canot reach 5000+ rpm

your timing at wot tells you you are indeed advancing.
the only thing that could be it would be your fuel.
double check the work you did with the fuel lines
leave the air cover off and run the motor to max rpm.
get some premix in a spraybotle and spray fuel into the trought of the carbs.
if the motor picks up you have defenatly a fuel problem.
as a said before if you think there is no fuel leaking out when presurizing it that doesnt mean it cant suck in air under vacuum.
an airleak could work the same way as a check valve. fuel presure closing the leak(when you prime thue bulp) vacuum sucking open the leak(when the fuel pump starts sucking fuel out of your tank.
especialy at higher rpm.
means more vacuum.

easy way to tell is put a clear vinyl hose same diameter between your fuel pump and fuel filter some where. make it air tight wit propper clamps.
run it as high as you can and check for bubles.

im having a feeling thats the problem.

dont asume its airtight check it out.

 

[reeldutch]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

if you have indeed bubbles it could mean 2 things.

1 airleak
2 vaporizing fuel deu to high vacuum caused bye a fuel restriction.

how do the plugs look like?
all the same or is 1 different than the other 3?

 

[jrousell]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

Weather permitting( have I mentioned we have had rain every day for more than a week ... ) I will try this afternoon.

I cannot thank you enough for your time and expertise!
Jeff

 

[reeldutch]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

no problemo.

i hope we will get it running good.
i'm sure we will.
we are on the right track.
hophely we didnt miss anything yet.

some people would be ripping of there carbs and start cleaning them and put them back on and find out it didnt help.

at least you are taking the right course of trouble shooting and it didnt cost you anything.
just a timing light.

so if im correct

idles at 4* atdc at 700/800 rpm without choughing.
that means its good and doesnt idle lean.
so your idle circuit in the carbs are clean.

full advance timing is at 26* wich is ok.
if im not mistaken the spec calls for 28 but because of ethanol and gas related things that might cause preignition lot of mech set the max advance timing to 24*.
so its not the timing or ignition causing the problem.
all 4 are firing strong without jumping around.

we basicly narowed it down to fuel delivery.

 

[jrousell]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

I just hoped ont o the boat at lunch real quick.

I use a premix spray bottle to squirt into the carb bores while moving along...

The top carboratior it had no effect on whatsoever.

The bottom carborator had the engine very briefly race a little faster. Not every time, maybe half of the time. and not for very long, but there was a decernable noise difference for a split second when I squirted directly into the bore


So does this mean that there might be some gumming up of a needle valve in the lower carb? or float issue?

 

[reeldutch]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

the only thing it tells you is that your bottum carb is running lean.
why we dont know yet.
could be:
- dirty main jet
- air leaking in feul line
- feul restriction
- gasket leaking

and that your top carb is not reacting to changes in fuel wich is strange.
can you better discribe what happened.

as i understand when you spray it in the top carb it has no affect
when you spray it in the bottum carb it picks up briefly?

because something aint right.
discribe exactly what happend and at what rpm you were wen you did this.

we might have something here.

 

[reeldutch]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

it should have some effect on the top carb to like bogging down or picking up briefly like your bottum carb.

if its not effecting it at all as what you stated i would do the same test again to verifie.
dont be shy sprayin the fuel in those motors are thursty at high rpm.

 

[reeldutch]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

also can you check all 4 plugs and dicribe per cylinder how they look like?

 

[jrousell]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

I will ahve to find a friend to try it agian- but here is what I found when we tried this earlier today.

it was at about 3000 RPMs when I tried this test. It won't get up to 3800 till it planes out, and with me hanging off the back it won't get up on plane so it maxes out at 3000 if I am hanging off the stern.


The top carb had no effect at all when I sprayed it. And I tried this at least 10 times. no bog, no higher rev, nothing.

The bottom carb - I could get a brief higher rev/burst. Just very brief, but it was definetly a noticeable sound and was very repeatable. If I sprayed even more I could probblay get it to burst even more noticeably


I'll go back and pull the plugs tonight to inspect again. And I will try to find a friend so that I cna try this spray bottle thing again.


Am I goign to be casuing any damage if I continue to run it like this?

 

[reeldutch]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

ok now i understand it better.

so you are saying if you would keep on continuing spraying into the bottum carb it would defenatly pick up more rpm's

and the top carb doesnt realy react to it.

try the test like this with your buddy.
but before you do the test check the plugs how they look like than do the test and recheck the plugs again.

my geuss is your bottum cylinders are starving for fuel.(not a good thing)

have your buddy run the motor and you just keep spraying gas in the bottum carb as much as you can. at 3000 rpm. keep on spraying with a steady spray to get the rpms going up dont stop spraying let the motor rev up as much and high as she can.
tell your buddy to look at the tach see if she picks up 1000/2000 rpm.

i'm pretty shure it will gain a lot of rpms.

than you know its defenatly the bottum carb thats running lean.
if it is i would rebuild both carbs and clean out the fuel system.

how old is your fuel tank if i may ask?
did you have old feul in it?
ethanol can do a good cleaning of the fuel tank only problem is it cleans it so good all kinds of debris gets sucked into the motor.
might have clogged your high speed yet on your bottum carb.

 

[jrousell]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

will do.

The tank is a built-in tank-probbaly new with teh boat in 1993. Gas in it is all new 93 octane. I also tried this with auxiliary tank of 87 octane with new lines and primer bulb...

I am tending to think that the carbs need rebuilding/cleaning too..
Not to get ahead of myself... but If this ends up being the case -- I am not sure if I am up to the task, or if getting a mechanic to ahve a look is worth it...

I ahve 4 small kids around, I can just forsee me having it al llaid out neatly on the workbench, kid comes along and wammo- part on the floor all a mess...


Is there any tuning that needs to be done, or is it just disasemble, clean, and reassemble with new gaskets etc...

 

[reeldutch]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

after you did all this trouble shooting and understanding why,

trust me putting in a new kit in a carburator isnt realy rocket sience.

its defenatly worth it.
a kit is about 35 dollars.
having a wrench do it at $90/hr
disambling cleaning reinstalling takes may be 3 hrs
plus parts yep thats about 400 dollars to do your carbs.

you can do both carbs yourself with help from this site here for 70 dollars just parts. and the best thing is you starting to realy know your motor and you can do it again if you have to.
but realy important when you clean and rebuild the carbs is not to leave the rest of the fuelsystem dirty. it will clogg the carbs again.

im not gonna be online after today for a few days
i will try but cant promise.

 

[jrousell]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

Thanks SOOOO much for your help.

hourly mechnic rates are kinda cheap up in this neckof the woods for small engine repair and the like.

If I could get an outboard mechanic to rebuild both carbs for say $150 -- it might be worth it for me. But you are right- if it were to cost me 200, 300, or worse 400 dollars I would do it myself and lean on help from others like yourself

Thanks again - are you going on vacation? - I hope you have some good weather

Jeff

 

[reeldutch]

Re: only 3800 RPM at WOT - loss of power under load -- please HELP

stop using 93 octane you are only wasting your money.
no need for 93.
only high compresion engines (high compresion ratio) need the octane for anti knocking.
your motor will be fine with regular 87.
its not going to have any bennefit to use higher octane than 87 on this motor/most outboards.
it doesn burn cleaner it doesnt have special aditives its just wasting money.