2003 75hp 2-stroke ELPTO Rough Idle with Video

[MonkeyBird747]

I’ve gone through quite a few threads/videos. Trying to avoid chucking parts at it at random, and looking for a place to start. Here is what I know so far.

1. Motor is new to me
2. fuel tanks, lines, bulb, and gas are all new and worked with previous motor
3. compression check with engine at temp. 107/105/106
4. plugs are the correct type by manufacturer specs
5. electric choke appears to be working

Im hoping the video gives some clues on where to start. I tried adjusting the idle mixture on the carbs, but it only helped a little. Haven’t had it on the water, and don’t have an rpm gauge (or any gauges) installed yet.

What I noticed during the carb adjustment was that if I closed off the bottom card mixture screw the engine would bog down and start to stall, at which point I backed it off 1-1/2 turns to begin further tweaking. But if I closed off the top or middle carb screws the rpms would drop, but it would still run. Don’t know if that is significant. PO reported rough idle, but smooth operation at other throttle positions.

Replacing transom at the moment, so lake test isn’t in the cards for a few weeks. Link to video below.

https://www.dropbox.com/s/h8cmpqw711...%2001.mov?dl=0

Based on research it seems stator/trigger could be a candidate. Maybe timing? Not sure where to start though. Have multimeter - will travel.

 

[emoney]

Try linking your video a different way. Can't open it without having DropBox downloaded.

 

[MonkeyBird747]

Here is Google Drive link

https://drive.google.com/file/d/14H-seRB8WLH6QDU-vk8ya-rcBRURrrqO/view?usp=drivesdk

and here is OneDrive link

https://1drv.ms/v/s!AmWdpg_AjC1qgq4Dvg2rLZuOzAqa7A

let me know if one of those work. Otherwise not sure how to link video.

MB

 

[emoney]

Are you sure it’s idling wrong because if it’s doing well under load and at other positions in the throttle range what you’re seeing could be bad motor mounts. Do you have a tac to co firm what rpm is at idle? I may still have the Factory Service Manual for my 90 and I think they’re pretty similar even though mine was an older version; 95. I chased similar demons on my 90 and finally turned out the upper mounts were bad. They’re not solid and therein lies the problem. Top ones are easy, bottom requires the head to come off.

 

[MonkeyBird747]

I haven’t had it on the water yet. Just the muffs. I know the final adjustment needs to be under load, but the PO has already reported rough idle, so I was hoping to address that on the front end. I can’t be sure the mounts are not contributing, but it sure sounds rough.

I’m a little surprised that I wasn’t able to starve out the motor by closing off the idle mixture screw on either the top or middle carb. I could only starve it with the bottom carb idle mixture closed.

 

[Faztbullet]

Aint nothing a lil in water carb adjusting wont fix...and those dont idle smooth anyways..what your seeing is typical idle for looper motor

 

[MonkeyBird747]

Aint nothing a lil in water carb adjusting wont fix...and those dont idle smooth anyways..what your seeing is typical idle for looper motor

Well I hope that’s the case. This motor replaces an ‘85 50hp Merc. I had to make some carb tweaks on that thing and it purred like a kitten at idle. Four cylinder instead of three.

 

[Watermann]

The compression is a bit low, most of the motors I've put money into were over 130 psi on each cylinder. Did you fog the cylinders before the test and or try another test after you ran the motor to see if the numbers came up?

Doesn't sound like the idle is very far off my 115 had a horrible idle issue that drove me nuts until I figured out it needed to have a link & sync done and the issue went away.. Have you done a link & sync yet, the spark plugs, what brand are they? It could be the carbs idle circuit has some gunk in them and a good carb cleaning with gasket replacement is most times all they need. I also always rebuild the fuel pump with a kit and replace the fuel lines if they transfer any black to my hands when rubbing them, it's just a cheap no future problems course to take..

 

[MonkeyBird747]

I've never used fogging oil before, but I just read up on it in my repair manual and I think I see what you're driving at. I did let it warm up at idle for a while and ran the check. That's where I got these numbers. However, I realized I did not perform the test at WOT, and I left the other two plugs installed during the check. I'll repeat the test with proper procedure from the repair manual. I found lots of various numbers, but it does seem 105 is on the lower limit of acceptable, but the fact that they are even is a little comforting. Hopefully I just dorked up the test. I'm sorta feeling my way through this.

Haven't done a link and sync either. I just looked that one up too. Looks pretty involved, but doable. I'll need to pick up a few tools for the job.

I thought about getting some carb kits and fuel pump kits. I looked at the old fuel line that I replaced when I bought it and it had a bunch of yellowish gunk in it. Maybe some of that junk made it into a carb. I'll put that high on the list to check and go ahead and pull them all and clean them up.

 

[Texasmark]

The manual states that idle is 675 +/- 50....fast enough to stay running, slow enough to prevent gear clunking. Idle is set with the idle screw on the spark advance arm......spark advance sets idle rpms.

Carb initial adjustment, per manual is 1.5 open then get on the water and punch out a hole shot. if it bogs, open all 3 a 1/16" at a time till it will take the firewall in the hole and stay online.

On rough idling, tilt the rear of the engine up a few degrees and see if that won't stop it....does on mine. Reason can be seen in the 1959 Mercury Mark 5 through 20 series of outboards....tilting the power head forward slightly keeps fuel from puddling at the plugs. I get a lot of scoffs on this but that's ok. I know it works because I do it every time I'm out and every time I do it in just a few seconds it's smooth as silk.......and I'm running a 4 cylinder where 2 cylinders are just bathed in fuel-oil till I get up around 2k rpm, so idling out of the launch, in the No Wake zone you are just coating 3 and 4 with mix.....yeah they are sparking, but no explosion hence no heat to burn off the residue.

 

[MonkeyBird747]

The manual states that idle is 675 +/- 50....fast enough to stay running, slow enough to prevent gear clunking. Idle is set with the idle screw on the spark advance arm......spark advance sets idle rpms.

Carb initial adjustment, per manual is 1.5 open then get on the water and punch out a hole shot. if it bogs, open all 3 a 1/16" at a time till it will take the firewall in the hole and stay online.

On rough idling, tilt the rear of the engine up a few degrees and see if that won't stop it....does on mine. Reason can be seen in the 1959 Mercury Mark 5 through 20 series of outboards....tilting the power head forward slightly keeps fuel from puddling at the plugs. I get a lot of scoffs on this but that's ok. I know it works because I do it every time I'm out and every time I do it in just a few seconds it's smooth as silk.......and I'm running a 4 cylinder where 2 cylinders are just bathed in fuel-oil till I get up around 2k rpm, so idling out of the launch, in the No Wake zone you are just coating 3 and 4 with mix.....yeah they are sparking, but no explosion hence no heat to burn off the residue.

Tilt trick is worth a shot.

 

[MonkeyBird747]

I have 12 gallons of recent pre-mix 50:1 gas that I don't need since the new motor has oil injection. Could I dilute this with some fresh gas and run it safely with the oil injection? 50/50 would be 100:1 I guess. I've read some run a little oil in the gas with oil injection anyway just in case?

Or would I be better off just disabling the oil injection and continue to use premix?

 

[Texasmark]

Any time onboard oiler gets repaired or anything that may put it in question, the answers on this site are always run 50:1 till you are convinced pre-mix works. Only difference would be a little smoke. I use Pennzoil Premium synthetic blend and you can't see it smoking. So doubling up would maybe produce a little smoke....especially at idle since the pump only puts out 1 part oil to 80 parts fuel....WOT is 1:50.

 

[MonkeyBird747]

Cool, I’ll run some premix then till I can get the OI checked out.

 

[Watermann]

Those oilers are very reliable on the lower HP 3 and 4 cyl Mercs of that era, personally I would not disable it. I ran my oil injected 115 with pre-mix 50:1 that was in a 24 gallon tank and the oiler at the same time. it smoked pretty bad ( regular QS 2 stroke oil) so I knew the oiler was working just fine and just started diluting. Been through a few tanks now and all is well.

 

[MonkeyBird747]

Thanks Watermann. I think I'll do the same thing.

 

[MonkeyBird747]

I repeated the compression check today using proper procedures this time. Engine warmed up at idle for 5 mins or so, all plugs removed, charged battery, and wot. 119-120 all three cylinders. I feel better about that.

Have fuel pump kit, carb kits, and lower seal kit. Going to run it on the water first and see how it goes. If good I’ll hold those rebuild kits until next spring.

 

[Texasmark]

I repeated the compression check today using proper procedures this time. Engine warmed up at idle for 5 mins or so, all plugs removed, charged battery, and wot. 119-120 all three cylinders. I feel better about that.

Have fuel pump kit, carb kits, and lower seal kit. Going to run it on the water first and see how it goes. If good I’ll hold those rebuild kits until next spring.

Per the service manual those numbers "meet the bar". You should be good to go on that.

 

[MonkeyBird747]

Tool it for test run today. Short trip! When I put the lower unit back on after water pump change I didn’t get the shifter meshed properly. I had two forward gears and no reverse or neutral. Going into reverse actually just kept it in forward gear and added throttle. This led to some entertaining antics while launching from a busy boat ramp .

Trailered home because I had every tool in the boat except the socket I needed. It was a quick fix. Some good came of it though. I decided to just go ahead and rebuild carbs and fuel pump, and change the inline fuel filter. He picture shows what was in the fuel pump. Is that some new record for amount of garbage in a pump? Fuel filter was full of it too. I’m guessing varnish or deteriorating fuel line from PO. Changed the check valve in oil/gas line too. I could blow through the old one easily from both ends. Not much checking going on in that valve.

Have a new thermostat, but forgot to order new gasket. Once that comes in I’ll go ahead and change that out too.

Now it runs like this. Sounds much better to me. No loping/sneezing. Three different links to video.

https://www.dropbox.com/s/3tvr9orcd9kd47i/Video Sep 12, 19 47 09.mov?dl=0



https://drive.google.com/file/d/1_Rk8F3EpPujc5812bqS4w7rKNbrAfbCO/view?usp=drivesdk



https://1drv.ms/v/s!AmWdpg_AjC1qgrEnzAGzMTJ_PdK0eg

 

[MonkeyBird747]