'89 60hp Merc. May throw in towel- Help me say no

Korbs67

Seaman
Joined
Apr 19, 2012
Messages
51
Hi All. I'm looking for some help before I decide to wash my hand of this 2 month project. Lots of $ and it has dominated my life for 2 months. I really want this motor to run like it used to. As interesting and fun as its been I'm just getting SO frustrated and I'm spending time on this instead being with my kids or on the water with kids.

If anyone has come across the issue below I could really use some guidance from this forum.

SN b396723

I'm in the final stages of the rebuild (rebuilt it now the 3rd time in 2 months). I have narrowed it down to a carburation issue. #1 keeps running lean. Anyway, I have really taken my time on this latest rebuild. I'm in the timing stage before i run it on water. I did a static timning with timing light. 23btdc. Took it to launch, on trailer I set up timing, idle, etc while on trailer. While running and in gear (tried in neutral too manually moving throttle) I accellerated and the engine started kind of choking and over revving, like the engine was getting away from me as I advanced the throttle to approx 200-2500 rpm. Kind of had that YZ80 sound coming down from a super high rev..if you know what I mean. Engine rpm very slightly varies at idle.

Notes:
New block- holes ball honed and are spec. (couldnt find the water leak into Cyl1 on my old block which was steaming detonating #1 several times so I replaced..no more water jacket leak thank goodness)
compression 130 all cyl.
Spark-Good 3/8 gap
Fuel- Seems to be flowing well. Pulses beautifully when looking at the stream just before carbs.I detached briefly while running.
New Plugs
Fuel pump rebuilt
Fuel lines are new
All ignition components spec out using DVA
Rectifier charges my battery
Battery is new
New water pump
Carb just rebuilt- Floats, needles, seats. Floats adjusted perfect. Jet sizes are correct.

Prior to carb rebuild the same thing happened. I thought rebuilding carbs would fix problem b/c the top carb needle was worn.


PLEASE tell me there is something obvious I need to do.
THANK you!

Korbs
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: '89 60hp Merc. May throw in towel- Help me say no

Anytime water intrudes a cyl you should inspect the exhaust plate to ensure the gasket seals the water side from the exhaust side. ANY CRACKS OR A WARPED PLATE OR BLOCK MUST BE CAREFULLY STRAIGHTENED, FILED, TO ENSURE A PERFECT SEAL. sorry, bumped the caps lock button.

Any lean cyl needs to check the carb AND the ignition. It is rare, but a switchbox CAN 'double-fire' a cyl, firing a second time on the intake stroke, causing that cyl to run leak and toast a piston. A spark test will only show a good hot spark.

An inductive tach should be used to verify consistent RPM on all cyls, any cyl reading twice should be obvious and cause for suspicion.

Always remember, there is NO RETURN on electrical parts, never assume anything, always PROVE any suspected fault BEFORE ordering any part.
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,590
Re: '89 60hp Merc. May throw in towel- Help me say no

I have narrowed it down to a carburation issue. #1 keeps running lean.
Only way this can be carburation problem is a bad,bad air leak into #1 cylinder(transfer cover). More likely a bad switchbox (bia's circuit) advancing timing at WOT. Index flywheel and check timing under a load on the trailer........
 

Korbs67

Seaman
Joined
Apr 19, 2012
Messages
51
Re: '89 60hp Merc. May throw in towel- Help me say no

Thanks for your help again Faztbullet. When you say index flywheel. Do you mean find TDC. I did that the old fashion way not with the TDC Guage. I'm very confident I'm accurate. I timed WOT at 23btdc. on at dock under load on trailer. took boat out on river, ran it WOT and timed yet again. I shut it down b/c I didnt like the lack of power thinking I was leaning #1 again..I'm gun shy because I've dentonated 2 pistons with my old block and dont want to ruin this new I have.


I swapped my #1 coil. I blew out my rectifier trying to fiddle with a tach issue. I put my old rectifier back on and my tach worked and passed ohm tests so maybe I never needed a new one. I changed those variables went back to dock thinking double coil firing was my issues and now it the engine races after about 2000-2500 rpms. I swapped back to original coil, rechecked fuel pump, bypassed fuel lines going straight to fuel pump from a 25:1 fresh can, clean and rebuilt carbs (as mentioned) and this revving issue still exists.

How would I test the bias circuit to verify or eliminate? I do not have the DVA anymore..

Thanks!
 

Korbs67

Seaman
Joined
Apr 19, 2012
Messages
51
Re: '89 60hp Merc. May throw in towel- Help me say no

Thansk Charlie B,
I got a different block so no more water issues thankfully.

My timing light is inductive but doesnt show RPM. So if I get an RPM reading twice the other cylinders I'm double firing? Or do you mean that the reading will flash or display twice on a digital inductive light?

I did swap #1 coils with another mercury coil(diff prod# hope it didnt ruin something). Anyway I marked tdc on #2 and #3 with a marker and didnt see two #'s so I assume no double fire there. #1 flashed no differently with replacement coil than the original that I thought might be giving me trouble. Timing light on #1 flashed at the same rate with both coils and relative the others according to my visual perception anyway. I know this isnt 100% but its all I could do. With either coil it still races as I increase throttle so if it is the pack I suppose it would tell either coil to act the same way.

IF a cylinder is reading twice what does that indicate?

Thanks!
 

Korbs67

Seaman
Joined
Apr 19, 2012
Messages
51
Re: '89 60hp Merc. May throw in towel- Help me say no

Hi Fatzbullit. Can I test this switchbox with a mutlimeter or swapping blue and red from stator, coil wires..something, anything?? ;)

THanks!
Korbs
 

Korbs67

Seaman
Joined
Apr 19, 2012
Messages
51
Re: '89 60hp Merc. May throw in towel- Help me say no

I borrowed an air compressor and really gave the carbs another cleaning and there is no more racing and skipping. Took to docks did timing routine. 2btdc at idle in forward gear and 22ish at WOT (3,000+ all reads the same WOT reading). Pictured is the where the timing mark lights up at.

In fear of another lean burn out my carbs were adjusted to 2-2.5 turns out.

On the trailer there was no lag in hole shot from idle position. BUT when hovering at 3,000 RPM it hesitates, drops 200rpms, then get to 4500 rpm on trailer when I go full throttle. My understanding is that if there is any hesitation in hole shot it means carbs are lean. I opened all the way to 2.5 turns out and still get them same slight hesitation.

ON THE WATER:
Seemed to be fairly peppy. It sounded nice. Got on plane better than my past efforts. Tested with carbs at 2-1/4 turns out. Ran about 5 minutes at 5k rpm trimmed. I turned off motor to check temp by hand. It felt warm, passed the 3-4 second hand test. I prob should've left it idling to keep water flow b/c it cooled a bit when I went at trolling speed.

Problem: On the way back in engine was surging between 4,000 and 5,000 RPMs. A rythmic surge up and down in that range with throttle held at what was to be about 4k rpm. I'M SO CLOSE on this motor. I consider this a success because I didnt blow it up again. LOL. ANy thought on what this surge is?? Something stuck in carbs again?..which leads me to think fuel supply (I have a new filter put in). OR switchbox since trigger tests just fine? or maybe trigger is on the fritz? I just dont think my iginition system is the issue. I WISH I could try a new switchbox without buying one!

ANy thought or direction is appreciated!!

Thanks
Korbs
 

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trogdog

Cadet
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Jan 5, 2010
Messages
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Re: '89 60hp Merc. May throw in towel- Help me say no

First let me ask the basic 1000$ question did you do a pressure test and a leak down test on the motor if need you need to before you are rebuilding it for the 4th time the reason it is running on is because it has a air leak some place and that is why it is leaning out the number one cylinder Here is a link for a little more info. http://www.klemmvintage.com/airleaks.htm hope this helps
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,590
Re: '89 60hp Merc. May throw in towel- Help me say no

Set your Max timing at 23? at cranking speed and this will give you 21? at WOT, engine will last a lot longer and you not see any performance loss
 

Korbs67

Seaman
Joined
Apr 19, 2012
Messages
51
Re: '89 60hp Merc. May throw in towel- Help me say no

Interesting read. Thanks for the link. If I tear this thing down I may do this test. it does seem essential. Whcih I knew about it before.
THanks
 

Korbs67

Seaman
Joined
Apr 19, 2012
Messages
51
Re: '89 60hp Merc. TIMING Quick help.

Re: '89 60hp Merc. TIMING Quick help.

Hi Faztbullet,
I definitely want to be at 21 btdc. In the attached photo what does my timing indicate? 23dg btdc is to the left or clockwise from my 0(zero)?? This may sound silly but I'm wondering if I'm on the wrong side of the 23 mark! Now that I look at it I think I've been timed at approx 25-26btdc.

Also- The manual (Seloc I think) says go 28 static to get to 23 which I found accurate. This morning I tried static at 23 the adjustment screw barely got me there..Something didtn seem right so i went static at 26. The problem is that I want to make sure that 21degressbtdc is to the right of the 23 mark as I mentioned above.

Cyl 1 is dry comared to 2 and 3 the plug isnt bone dry but its not as wet as 2 and 3. Something tell me my leaness is because I'm timed at like 25 instead of 21.

Also, interms of fuel what would you recommend, I run 87octane with a 25:1 mixture during the breaking of my rings. Should I go to 89 or 91 since I'm timed at 21??

THANKS to anyone who might also read this thread.

Korb
 

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CharlieB

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Re: '89 60hp Merc. TIMING Quick help.

Re: '89 60hp Merc. TIMING Quick help.

The marks to the left of 23 are 24, 25, 26, etc. The motor turns CW, the #'s will keep getting smaller until you reach TDC.

You have been running #1 LEAN and toasting the piston.

Have far into the fuel system have you gone?

A weak fuel pump, OR air sucking into the fuel system anywhere in front of the fuel pump, and #1 carb cannot stay FULL AT WOT, it goes lean and toasts the piston.

Temporarily install a clear hose between the fuel pump and the carbs, run the motor and watch the hose for any air bubbles passing thru.

Bubbles prove a problem, find that and seal it.

Aged quick connect fuel fittings can suck air past the o-ring yet not leak a drop of fuel.

A crack in the fuel tank dip tube will suck air along with the fuel.

You need to check everything.

Your ignition may be fine, just adjust timing while cranking to the 23 mark or just a hair right of it.
 
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