85 15 hp..issues

[SCduckhunter]

So i had an overheat....i replaced the entire cooling system....water pump,impeller, both upper grommets, thermostat, all the gaskets..i had 108# psi on compression test prior to tear down and repairs....( motor was litteraly running 2 mins before i broke it down)...it sat for 6 weeks or so torn down while waiting for parts....i put it together today....i have installed a brand new power pack and cleaned and resurfaced all the gasket surfaces...rings and pistons were in good shape...ive puta new fuel pump and all fuel lines and carb rebuilt with in last 10 months...all that said i took her out today after the fix....she starts and idles great...compression tested to 110# on both cylinders...after i backed away from dock and put into F she didnt respond to throttle....than took her sweet time getting up to speed..which she never really did...ive burned 100 s of gallons of fuel in this boat with this motor.. i know it well to say the least...anyway, she never got to full power...coil pack breakdown is possible due to aforementioned overheat.. possible i pinched or overtightened something on throttle plate? She does seem a bit harder to twist throttle...possible that i jumped teeth...? Or is it something deeper like reed valve ...i just dont know where to look and since this isa new to me issue im not sure what to eliminate first thats easy..towards a fix...anyhelp or ideas on where to look into please and thanks

 

[Daviet]

Re: 85 15 hp..issues

Welcome to the forum.
Your compression looks good, the only thing left is spark and fuel.
I would check and make sure you have spark on both cylinders under load, sometimes an overheat condition can cause an electrical component to fail under load. If the spark is working OK, try spraying some fuel mixture into the carb and see if it picks up.

 

[SCduckhunter]

Re: 85 15 hp..issues

After work today i ran out and it cranked up no problem....i let itwarm up and when it started to run bad i shut it down and unplugged#1 plug it ran real rough... switched it to unplug#2 and it ran decent....i flipped plugs around and retested.. it did the oppisite....plugs are gapped correctly and were new the day of the overheat...im guessing the overheat caused something to screw up that plug...im off and plan on running it inthe river tomorrow..hoping thatll solve the extremely slow throttle response...we shall see...if not it maybe a coil since power pack was delivered and installed about 30 hours ago

 

[Daviet]

Re: 85 15 hp..issues

What plugs are you running?

 

[SCduckhunter]

Re: 85 15 hp..issues

Champions....the correct ones properly gapped...im pretty good with this stuff usually..since this issue arose post overhaul.. could i have misaligned the throttle cam and the gear at the throttle when reinstalling powerhead? Theres also the possiblity of a failing #2 coil pack after it warms up correct?

 

[SCduckhunter]

Re: 85 15 hp..issues

Sorry ...dont mean to be rude... hi im chris and new here....lurked quite a bit while overhauling this motor and now im at an impass....and not to be confusing the bottom (#2?) Cylinder is the one that ran poorly when i removed plug wires and swapped plug locations...

 

[SCduckhunter]

Re: 85 15 hp..issues

Ok..update and thanks so far for the direction....after i did an air gap spark test with engine at temp spark was defiantly weak on #2.. replaced coil pack and put plugs in her at .30 this morning....cranked her up she idled a bit rough but smoothed out...backed her off trailer. I shut it down so i could see how she ran cold from the hole and if itaffected performance to the good orbad....parked truck went down.and cranked right up...put her in F and gave her some throttle....same as before....took 10-15 seconds for rpm to come up and never got to full rpm....well i decided to play with the screw in front....i.leaned her out a good bit and goosed her...she responded instantly! Theres hope! She would then bog back down and run under full rpm...i backed off throttle to 3/4 and she still didnt respond well...full throttle long 1/4-1/2 mile runs shed surge to full rpm and run great 5-10 seconds at a time...the entire time i played with idle screw and knew that all the way in tight then.backed out to 1 1/2 turns was where she ran best before...she ran ok...i pulled alongside dock backed trailer in and she choked out when i went to pull off....she was hard to restart...finally got her going after riching her out and loaded her..she responded to throttle well... i put her in N and sat for a ibacked her offand spun aroumd and gave her gas she jumpedotta the hole and nearly came up to full rpm...i did this several times....and the respomse was the same....im not great with carb adjustments but that what it now seems down to...whats best way...i put a rebuil kit in her18 months ago (aprox175 hrs ago)..checked plugs and compression again when i got home with a bwtter tester and got a 4# lower reading of 104# on #2 cyl and the plug with aprox 1 hour run time was signifigantly dirtier than #1 plug..both brand mew 2 hours prior...im sure the psi difference is a ring going bad bitthe dirty plug seems to be just a motor thats too rich?? Running 50:1 ratio with 2 day old marine fuel...anydirection.would be great minutminute..checjed primer bulb and fuel tank vent.
she idled great.

 

[SCduckhunter]

Re: 85 15 hp..issues

Btt

 

[Daviet]

Re: 85 15 hp..issues

Does your fuel pump mount on the lower cylinder,#2, by chance?

 

[SCduckhunter]

Re: 85 15 hp..issues

Yes...it mounts oppisite of starter...ran it today after a carb cleaning 2nd this week....it fouled the #2 plug pretty good within 10 mins...it is respomding to throttle....now it just surges and wants to get up and go..it just wont....

 

[SCduckhunter]

Re: 85 15 hp..issues

Fuel pump was a previously suspected for a different problem so it was replaced 12-14 months ago...

 

[SCduckhunter]

Re: 85 15 hp..issues

While out testing earlier i removed the main cowling..i heard what sounded to be a spark or short...upon inspection i found a small spark on the bottom of #2 coil!. I changed the bolt and washer location...it didnt spark that i could see or hear...i ran it again and still no change in.performance...what is the correct mounting for coils? Asbestos washer washer coil washervolt thru all..asbestos washer against block so bolt is ground to block? block

 

[SCduckhunter]

Re: 85 15 hp..issues

The more i play with it the more it seems to only be running on one cylinder most of the time....great spark amd fuel to both cylinders...good compression too..i just dont know what to make of it

 

[SCduckhunter]

Re: 85 15 hp..issues

More play in the dark tonight...runs with either plug wires undone...so its firing on both cylinders....back to fuel delivery issues im guessing

 

[Daviet]

Re: 85 15 hp..issues

I would remove the fuel pump and pump up the primer bulb and see if any fuel comes out of the pulse port for the fuel pump.
If the diaphram is leaking it could be flooding #2 cylinder.

 

[SCduckhunter]

Re: 85 15 hp..issues

Ok will try that tomorrow after work thanks!...oh whats the best (read least destructive) method to remove and replace the plug in the carb....i saw it mentioned somewhere here..in the 10 years of owning this motor ive done all the work and know for a fact that i havent removed it...im guessing that theres a small hole or orificein there that can/ should be cleaned

 

[Daviet]

Re: 85 15 hp..issues

You are correct, there are small holes in there that have to be clean.
There are a couple of ways to get the core plug out.
1. Use an 1/8" drill bit and drill through the plug, don't go any deeper than necessary to go through the plug, and then use a punch or pick and pop it out.
2. Use a 1/8" punch, support the carb body on the jaws of a vice with the float pin bosses between the jaws, and just tap the punch through the core plug and pop it out. The core plug is made of soft material and a punch will go right through it.

 

[Chinewalker]

Re: 85 15 hp..issues

Your issue is not related to idle circuit.

 

[SCduckhunter]

Re: 85 15 hp..issues

That's idle circuit under welch plug?...I'll try to test fuel pump for leaking diaphragm today

 

[Daviet]

Re: 85 15 hp..issues

Yes, the idle circut is under the core plug.
Chinewalker is correct that your problem is not in the idle circut.