1978 85 hp not making WOT...

[relocyo]

i took my 1978 85 hp johnson #85ml78c out first time after repairs, it ran beautifuly but 1. it ran at 3000 rpms with control throttle arm at 1/2 , and around 30-35 mphs 2. when i advance the throttle arm to WOT it reduced rpms and speed and seemed like i had decreased the throttle, but when i move from WOT back towards idle speed, about halfway to idle it jumped back up to 3000 rpms and 30ish mph... in short, about halfway thru its range is WOT for me...

recent repairs:
rebuilt carbs
new plugs
new fuel pump
new coil on 1 cylinder
new gas
clean gas tank
compression good on all cylinders

i had an air leak that i believe i fixed so that shouldnt be an issue i dont think, i adjusted the idle on muffs in the yard, and what i consider "lync n synch" at the same time, i just found out thats not the right way to do it but i dont think that should be causing this problem but i dont know...

any ideas on whats going on? thanks yall...

 

[Barnacle_Bill]

Re: 1978 85 hp not making WOT...

Start off by doing the link & sync properly. It must be done in the order given in your manual.

 

[relocyo]

Re: 1978 85 hp not making WOT...

well thats kinda the thing though, in my seloc manual it says my year and my year only doesnt have the link n synch capabillities... i know that sounds weird but thats what it says...

is there a generic link n synch procedure i could use?

 

[emdsapmgr]

Re: 1978 85 hp not making WOT...

That's probably why most of us prefer the factory manuals over the aftermarket ones.

 

[ezeke]

Re: 1978 85 hp not making WOT...

Take the air silencer cover off and watch what's happening at the engine while someone else moves the control arm from neutral to full throttle.

The timing advance should move with the throttle. The cam follower roller should be centered on the mark on the cam but not quite touching the cam. The throttle plates should all be fully closed.

As the arm moves, the throttle plates should move precisely together, and should reach a perfectly horizontal position at WOT, and move no further than horizontal.

 

[relocyo]

Re: 1978 85 hp not making WOT...

thanks for the help... what happens while looking at it is, at about half throttle the timing arm bottoms out/ stops moving, and the throttle continues to open the throttle plates to the proper horizontal position... does that sound right? because like i stated in the original post half throttle seems to be my WOT... thanks again yall...

 

[ezeke]

Re: 1978 85 hp not making WOT...

When the throttle plates are horizontal, that's WOT, that's wide open.

When you move the control arm forward it should shift into gear. At about 30-40 degrees from the perpendicular, the throttles start to open.

 

[emdsapmgr]

Re: 1978 85 hp not making WOT...

You will find the engine goes to full (max) timing advance first, then the carb butterflys continue to open as the throttle increases. What your are describing is normal. It is possible to mis adjust the carb butterflys so that they continue to rotate beyond level (full throttle) and can actually close somewhat. Are you sure the high speed jets in the carbs are not restricted? When you cleaned the carbs did you remove those jets and inspect them for dirt/debris?

 

[relocyo]

Re: 1978 85 hp not making WOT...

thanks guys, my particular setup is i have2 handles on my controls one for shifting the engine and the other for the throttle (i know dark ages) but that what im stuck with... thank you for the carb advice i did clean the high speed jets and the butterflys work properly as youve described, i still dont understand why im only making 3000 rpms and 30 mphs... im headed out now to take her for spin/fishing trip... ill let yall know if i need a tow... this will be my first trip beyond a paddleable distance from launch point... wish me luck!!!
but if anyone has any other ideas about why im not making full rpms/mphs please let me know....

 

[emdsapmgr]

Re: 1978 85 hp not making WOT...

What happens when you advance the throttle to full advance and someone constantly primes the fuel hose bulb at the same time? This forces extra fuel around the pump, directly into the carb bowls. When running, that hose bulb should be soft, but not collapsed.

 

[relocyo]

Re: 1978 85 hp not making WOT...

i will give that a try next time... if thats to test the fuel pump, its brand new and seems ok, and the fuel bulb and lines are all new, bulb is firm and stays firm even overnight... it just seems to me after the timing is advanced all the way (with butterflys partially open) it just doesnt go any faster, it actually goes slower with lower rpms when i advance it past half way...

but besides that the boat ran great today i had it at what for me is wide open for over an hour with no ill effects... so for the first time im feeling good about this motor, i just need to figure out this last little problem... thanks again...

 

[emdsapmgr]

Re: 1978 85 hp not making WOT...

Part of the reason to prime the hose bulb is to see if there may be a fuel restriction in either the anti-siphon valve (on a built-in tank) or in the fuel pickup inside the tank. It's unusual for the hose bulb to stay hard for such a long time. If you have a built in tank, the anti-siphon valve can stick if it gets any debris in it-restricting fuel flow. It would seem that when you continue to open the carbs, they ingest more air, but perhaps no more fuel. That can create the bogging. When you had the carbs apart for overhaul did you remove all the jets and visually inspect them? Esp the high speed jets? When you open up the throttle and the engine bogs are the plugs wet or dry? Sure you have the correct fuel pump on the engine?

 

[relocyo]

Re: 1978 85 hp not making WOT...

hmmm you def. make a good point about maybe it getting air but no fuel at wot... as for the high speed jets i would say i cleaned them well enough but thats hard to say for sure i guess... which ones are they and what should i be looking for? some type of gunk clogging them up i suppose? like i stated earlier its a strange thing, as i throttle past half way its just like i was throttling down, it doesnt neccesarily "bog" its just like i reduced throttle...

next chance i get i will try and squeeze the bulb to see what happens, im guessing it should increase my rpms/mphs?

well thanks for the help i guess ive got a couple of things to look at now...:redface:

 

[ezeke]

Re: 1978 85 hp not making WOT...

The high speed jets are at the bottoms of the float bowls, behind and in line with the plugs.