1994 MERC 90HP ELPTO - WON'T STAY RUNNING UNLESS FAST IDLE LEVER UP - PLEASE HELP

[mrecho76]

Hello Everyone,

Thanks in advance to anyone who might be able to help!

I purchased a '94 Procraft V-170B with a '94 Merc 90hp ELPTO. The boat was sitting for 5+ years and I know there's a lot to do to get her running again. I did most of the maintenance items but I can't get her to stay running unless I have the fast idle lever up.

Here's what I did so far:

1. Compression test before anything - 105psi on all 3 cylinders.
2. New Spark Plugs
3. New Thermostat
4. New Impeller
5. Lower unit gear oil change
6. Power trim oil level check
7. Rebuilt all 3 carbs with full rebuild kits - (cleaned with Chem-Dip & carb cleaner)
8. New Fuel Filter
9. Rebuilt fuel pump with rebuild kit
10. Inspected all fuel lines and replaced those that needed replacing
11. Drained and filled oil reservoir with new 2-stroke oil
12. Checked all oil line hoses
13. New Battery
14. New Starter
15. Temporarily hooked up to a separate 3-gallon tank with fresh fuel premixed to 50:1

Things I still need to do:

1. Spark test
2. Timing
3. Adjust carbs (been trying)

So I believe I did most of the items that's required but I can't keep her running on idle speed. I've done a lot of research and every answer seems to point to something that I already did (usually carbs). I'm wondering if it is in fact a carb adjustment issue? According to the service manual, after rebuilding carbs, you should start with the slow idle screw turned out from a close position as such: top carb - 1 turn, middle carb - 1 1/2 turns, lower carb - 1 1/2 turns. Then the motor should run. You then adjust as necessary.

My problem is I've tried that, I've tried as low as 1/2 turns on all 3 and up to 3 turns on all 3 carbs, but nothing I do is working. After all the repairs I've done so far, the motor starts great (with a little priming on cold starts), but only will stay on with the fast-idle lever up. When I try to back off the fast-idle lever to regular idle rpms, the motor bogs down and dies (even after minutes of warming up).

What could it be? Could it be a carb adjustment issue? Spark issue? Timing issue? I think I read somewhere maybe Reeds? Any thoughts would be appreciated!

Thanks again,

E.C.

 

[roscoe]

It really would help to know if all plugs have spark. That will eliminate electrical from the equation.

 

[Texasmark]

I was going to say to check the fuel line to the tank, especially if the gray OEM silicon (looking/feeling) fuel line but I assume you changed tanks at the connector mounted on the front of the engine so that takes that out. However, you might take that connector and force it open with a non-marring instrument like a popsickle stick and with it pointed into a container where the gas can be monitored, using the squeeze bulb, force some fuel into the container.

If the fuel has tan chunks of residue, it's your fuel line degrading and it and the bulb need to be replaced along with your internal fuel filter....white on the port side of the engine between the fuel pump and the carbs. One would think that if this is the problem and the fuel filter is clogged it would affect high speed operation. I'd think that too but at low rpms, the fuel pump isn't putting out a lot of volume and maybe it is part of your problem. Course squeezing the bulb at idle would assist the fuel pump in supplying fuel so it it worked while squeezing then you could investigate what I mentioned.

 

[mrecho76]

Hello guys,

Thanks for the responses. Well I did another compression test and am getting 125psi on all 3 which is great news (the first compression test was done when I first got the boat before I did anything). I'm surprised to see such a jump, maybe the new starter helped, or one of the items I performed, or maybe I just didn't do it properly the first time.

Anywho, I did check the spark on all the plugs and each plug is getting a strong bright blue spark. So it seams the spark isn't issue. I tried adjusting the slow idle screw again, starting with 1 turn out on each all the way up to 4 1/2 turns out on each. It's the same thing either way. The motor seems to run smoothly at higher rpm's (with the fast idle lever raised), but as soon as I start to come close to regular idle rpm's by lowering the lever slowly, it starts to bog down and eventually shuts off.

I found a sweet spot with the fast lever idle slightly raised where the rpm's aren't too high and the motor stays on, but it's nowhere close to idle (probably around 1500-2000 rpms). If I drop below that, the engine dies.

I also tried lowering the fast idle lever very slowly while continually squeezing on the fuel bulb, but that has no effect. By the way, the gas tank fuel line on the 3-gallon I'm temporarily using is new, along with the bulb.

So again, having rebuilt all the fuel components, and checked/replaced all the fuel lines, I don't understand why it won't stay on at idle. I'm wondering if I need to rebuild my carbs again? I took my time and rebuilt them thoroughly, making sure to dip them for an hour or so each, cleaned out each hole and passage with carb cleaning, then ran compressed air through all. All the passages seemed open when I blew air through them (I would feel air on the other side).

I don't know what to do next at this point, the only thing I haven't done is check the timing. Could that be it? So confused... =/

Thanks,

E.C.

P.S. Could you guys bump this thread to keep it fresh? Thanks!

 

[racerone]

Check the flywheel key.---------You might want to pull the exhaust cover off to do an inspection.---Possibly a cylinder sleeve is out of position.----Remote , but it is possible.

 

[Texasmark]

Racer......is the cast iron cylinder liner not locked into the block casting like most other cast iron cylinder liners?

Mr. 76 something you said lit a fire. Disconnect your remote control throttle cable at the engine. Push your engine throttle lever....the one the remote was hooked to, all the way back......idle position.

Do a link and sink setup on the carb and spark advance linkage (in your service manual) then start your engine on muffs. With the carb low speed jet screws set to 1 ? to 1 ? turns out from a soft start (2 finger tight), set your idle screw....the one that moves the throttle linkage from the remote control hookup point for an idle rpm of 675 +/- 50 rpm (manual number).

Set your remote control shift/throttle lever to Neutral position. Go back to the engine and hook up the plastic end of the cable to the pin on your engines throttle lever and secure it with the self locking nut and washers. Look at the position of the brass barrel on the brass threaded part of your remote cable. If it doesn't line up with the plastic hole on the engine then you may have found your smoking gun.

Without moving anything else, spin the barrel up or down the threaded hollow rod until it lines up with the hole and push it in and secure it.

Go give that a try. Your idle rpms are set with the control I mentioned earlier and it varies engine timing. To set your carb low speed jets properly, you need to be in the hole and firewall the throttle. If it won't take it, open the screws a little at a time (1/32 turn) until it will. Get this done and you should be good to go.

Your compression numbers are 5 psig above what the manual considers the Ok/start worrying compression point.

 

[Faztbullet]

Racer......is the cast iron cylinder liner not locked into the block casting like most other cast iron cylinder liners?

Its a interference fit against aluminum block its not cast in place....

 

[Texasmark]

Its a interference fit against aluminum block its not cast in place....

Thanks Faz interesting. What makes them come loose, overheating, low oil ratio?

 

[mrecho76]

Hi Texas,

So I synchronized the carbs, did the timing, and adjusted the throttle cable, but still have the same issue. I do have a question regarding the timing though. According to the manual, the idle timing was to be set at 5 degrees BTDC and they have a small picture showing the numbers increasing to the right from 0 - 8. But from my understanding, when setting BTDC, you go "left" of the 0 no? Like 8-6-4-2-0..not 0-2-4-6-8 correct? Well that's what I did and I'm hoping that's correct. So for the idle timing I set it at 5 degrees left of the 0 mark, and the max timing I set at 20 degrees left of the 0 (all done with cranking on a full battery charge).

Assuming that I did the carb sync and timing correctly, I'm still having the same issue where I can't back off the fast idle lever to a regular idle. If I try to start it without the throttle advanced a little (like if the throttle cable wasn't even hooked up), then the engine won't start.

ARG!

E.C.

 

[Texasmark]

To determine which way to go on timing, the engine turns cw and the timing light is telling you when the plug gets hit. To be BTDC you have to light the number before TDC gets to the arrow (scribe mark, white line, whatever the timing marker is) so I agree that the numbers would be to the left as you physically go around the circumference of the flywheel. Walking through it, your timing light shows you a 5 under the marker when #1 hits and 5 degrees later you are at TDC. Same on the WOT.....you see a 20 under the marker and 20 degrees of CW rotation later the TDC line runs by the marker but you don't see them because the plug has already fired.
--------------------
Let's build the building one brick at a time.....aka basics.

What happens when you use your fast idle?

Go to the engine and look at the engine linkage with throttle/shifter in N and the Fast Idle lever all the way down. Take measurements on the throttle arm in the engine to get a benchmark. Then go and raise the FI lever as you normally do. What happened to your measurement? If you measured the pin where the center plastic adapter (with the hole in it) slips over the deadman stud, distance to the outer barrel of the cable, the distance should have increased somewhat.

At that point start the engine and get a timing number off #1. Guessing it would be roughly 10 BTDC. What about your carb butterflies? I doubt they would be cracked....obviously noticeable that the butterflies were resting against the venturi castings of the carbs.
------------------------------------------
With what racer 1 said about the woodruff key, let's think about that.

The crankshaft diameter guestimate where the key is installed is ?". If I'm too wide the answer below will be in our favor. If too narrow, it will be the opposite.

So the circumference around the circle where the key is located is ? x pi. = 2.4"

The Woodruff key is probably ⅛" square or half moon with that thickness. The ratio of the circumference to the width of the key is .125/2.4 = .052.

Assuming you advanced the timing from 5 BTDC to 10 BTDC when you moved the fast idle lever, the ratio of that 10 degrees to the full 360 is 10/360 = .027.

These numbers are real close meaning that what Racer said about the Woodruff may be your smoking gun. They are close enough to warrant an inspection.

You may be able to just remove your flywheel nut, without having to actually remove the flywheel and peer down along side the crankshaft and flywheel looking in the flywheel grove you should see the top of the key. If you see ANYTHING other than perfect alignment of the slot in the crankshaft and slot in the flywheel, aka distorted key, you need to pop your flywheel and replace the key.

Flywheels are deliberately high mass components made that way to smooth out the power stoke impulses and make for smoother engine operation. Considering the Kinetic energy in the flywheel at WOT for a number, striking an underwater object can and will cause the flywheel to shift it's position with respect to the crankshaft and in doing that cut into the key and distort it. Distorting the flywheel to crankshaft relationship changes engine timing, and as I said earlier, this engine is set up at idle with timing! If you ever hit a rock with your lawnmower thus killing the engine and it wouldn't start afterwards (due to a partially or fully sheared key) you will know what I'm talking about.

Check it out! Otherwise, I'm out of guestimates.

Good luck.

 

[mrecho76]

Texas,

Wow, thank you for all that information! I'll trying looking into that next chance I get. I'll post again when I have an update.

Thanks again,

E.C.

 

[Texasmark]

Texas,

Wow, thank you for all that information! I'll trying looking into that next chance I get. I'll post again when I have an update.

Thanks again,

E.C.

Do that. I would, and surely anyone following this, would like to know the smoking gun.

 

[enginepower]

Just something to add if not said already. Not sure of the jet and passage sizes but sometimes soaking a carb is not enough. You have to get a guitar string/piano wire and poke through to loosen gunk sometimes. Hoping you used new gaskets on carb mounting surface. A leak between carb and engine won't allow good idle operation.

 

[wn6ngp]

If you are suspicious of a leak between base of carb and the intake then while its running spray some wd40 around the carb gasket and see if things change. If they do then it means there is a leak around those gaskets where you sprayed. I have not tried this myself but I've seen it suggested elsewhere and it makes sense to me.