91 Mercury 115 Rebuild - Let's see how it goes!

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

It's going just fine!
Not sure I should resurrect an old thread, but this is a thread I started and haven't finished. Apparently this will be a 3 week project spread over 3 years.
During the last installment I discovered I had received the wrong piston and rings and was waiting on the correct ones. Those came and then summer happened again.
I started reassembly last weekend. I put in the new piston and rod and new rings on the other three, put those in the block with the new bearings. That wasn't too difficult, but putting in the piston pin retainers was difficult. I finally figured out how to do it with needle nose pliers and a little finesse. I'm waiting on some fresh crankcase sealer before I button up the crankcase.
Tonight I tore the fuel pump apart to clean it up and put in the new gaskets. AND I found another assembly boo boo during the 2009? rebuild. One fuel pump gasket diaphram was assembled in the wrong order and the other diaphram is for an engine WITHOUT oil injection. You can see the bulge where the oil was pushing on the diaphram but without the holes to let the oil through it just bulged.
How did this engine ever run on the water?
This was a freshly rebuilt powerhead with new #3 piston and rod and all new oil injection components manufactured in 2009 (going by build dates on various stickers).

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Finished power head assembly. After all was assembled I had a one grommet left over. After quite a bit of research I found it was the popit valve seat. Oh well, pulled of the thermo cover and put it in there.
Now I am just waiting for some warm weather to paint the head and also waiting for misc parts.
The fuel pump oil injection has a bad check valve. I can feel the spring working with a toothpick, but the valve just won't check.
It's going to be cold here so probably a week or two before I can paint. Then a day for final assembly. Then I need to swap motors on the boat. OR buy a boat side wiring harness, etc. so I can break it in on my engine stand.
What is the recommended break-in procedure? (New #4 piston, rod, rings an and new rings in 1,2,3.)
Oh, but the way, forgot to mention that during the 2009 rebuild bolt number 23 in this tightening sequence was forgotten and not put in!

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Finally some warmer weather so I could paint the block. Unfortunately I forgot to take before pictures. It looked pretty bad but looks a lot better now.

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Upper and mid sections together for the first time in two years.:joyous:

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Starting to put all the peripherals on. I had a little slow down because I thought I cleaned the gasket material off of the manifolds and reeds two years ago, but didn't. Got those cleaned up, then found my accelerator pump was frozen. Cleaned that up, but will order a diaphram anyway because the old one is, well, old.

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Today I installed the stator, trigger, flywheel, electrical plate, temp sensor, and temp switch. Tried to install the warning module but forgot how the wires run so not completed. Tried to install the enriching valve, but found it was installed in the wrong location originally and haven't decided whether to move it to where it should be or put it back where it was. The factory manual for these steps is a little weak but I am getting it sorted out.
Hopefully I'll have it all assembled by this weekend!

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

I just about have it reassembled. Only need to hook up the wiring and then put it on the boat. I have the timing mark set, etc...
Had some trouble with the fuel inlet. It would NOT go in the grommet. The grommet was hard as rock. I put it in a cup of water and put that in the microwave until it was pliable then it slid in ok.

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

My oil pump doesn't have the timing marks as in the manual. It has a notch. It appears that I have it indexed correctly. Does anybody know?

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Completed wiring installation. Forgot how some of the wires ran, but got it sorted out. The thing that took the longest was cleaning each of the lugs, screws, nuts to ensure I had good connections.

Now all I have to do is build another engine stand to put the I6 on while I transfer this one to the boat!

 

[K-2]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Nice work! I am finding this very interesting.

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Thanks for the post! My original supporters deserted me after a year or two.

Yesterday I completed all the little things and fortunately remembered to clean out the tilt tube BEFORE I mount the engine on the boat (while there is room to work). You can see some of the junk that came out on the paper towel. I used a dowel with a slot cut in the end and steel wool wrapped around it which someone had previously posted here in the forums. Honed with some oil and it turned out great inside (just like cleaning up an old shotgun barrel).

Lastly I built another engine stand to put the I6 on when I do the motor swap. I made this one more like the plans on iboats except a little taller.

Now I am all ready to swap motors mounting this one on the boat and start the break in.

I'll do a short video of the first engine start. That may be in a week or so depending on weather.

 

[justchecking]

My break in plans:

My break in plans:

Based on info from the iboats forums and maxrules, my break in plans are as follows:

At home:
Input fuel: 33:1. With oil injection this should be ~25:1. Run engine for 5 minutes at idle. Stop and check for leaks.
Input fuel: 33:1. With oil injection this should be ~25:1. Run engine for 20 minutes at idle. Check idle timing. Stop and check for leaks.
Input fuel: 33:1. Disconnect oil injection and using graduated container check oil pump volume per manual. Run engine for 20 minutes at idle. Without oil injection, because pump is pumping into a container, this should be 33:1.

At lake:
Input fuel: 50:1. With oil injection this should be ~33:1. On trailer run engine from idle to about 1500 RPM loaded until about 2 hours run time.
Input fuel: 50:1 With oil injection this should be ~33:1. Check timing. On lake cruise from idle to about 3500 RPM loaded with short runs to full throttle until about 10 hrs of run time.

Any thoughts? Also does anyone think my oil pump timing is correct or incorrect?

 

[justchecking]

Re: SUCCESS! First start!

Re: SUCCESS! First start!

Was in a hurry and didn't take too many pictures. I have one of the 1984 coming back off and the 1992 just mounted. I also installed a tach hour meter. I took a pic at what was supposed to be zero hours, but it says zero RPM. I'll check that tomorrow.

THEN I STARTED IT! It started the second try and idled GREAT. After it warmed up (about a minute) it climbed to about 2000 RPM so I shut if off. I tried closing the carb needles a quarter turn (starting at 1-1/2) but it backfired once so I put them back at 1-1/2. I then tried retarding the timing and backed it off to about 4 deg ATDC. Got idle down to around 1500. Then realized it was supposed to be idling at 2-4 deg BTDC. So I had a beer and thought about it. No answers.

Any ideas on why it is idling so fast?

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Thought I had the idle RPM figured out. The motor I took off was a 6CYl. The one I put on was a 4Cyl. I figured I had to switch the tach back tp 2P4C or something. Tried various settings on the tach, but no luck. The original sticker on the tach is unreadable. Appears to be a teleflex, though, and from what I could read the settings do NOT match the current manuf tachs. Still wants to idle at about 1800 RPM on the tach. (I put the timing back at factory spec 2 deg BTDC).

Also, does anyone know if the plugs fire ONCE per revolution or TWICE per rev (as cheap 4 strokes do)? The aux tach I added also isn't reading right (or does doesn't appear to).

Anyway, idles GREAT, starts first try. If I can confirm the idle is correct I am going to measure the oil pump output volume next. I have about 30 min on the motor now.

 

[EMC 1810SS]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

My Tach gets it signal from the stator not the ignition. (a 96 115 4 cyl) I am pretty sure I set the dial in the back to 6. It was WAY off before I reset it.

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Thanks, it's been rainy here. Hopefully saturday I can take another look at it.

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Bought a new handheld laser tach and confirmed the engine is idling fast at about 2000 RPM. This is out of the water on muffs with timing at 2 deg BTDC. I can retard the timing and get it to idle down to about 1500, but then it backfires and stops.

Also confirmed the trigger is firing correctly on all four cyls with a timing light.

I have about 1.6 hours on it now. I have a question about spark plugs separately posted...

I still have to measure the oil pump output, but that is supposed to be at 700 RPM so...

Oh, also had to replace the fuel connector because the old one was cracked. I replaced it with factory spec part # 816856Q3. Then when I hooked up from the boat side found the boat side seal was leaking. Then I found (after buying a MERCURY boat side connector which didn't fit) that this is apparently a YAMAHA connector. Anyway the Yammy connector fits and does NOT leak.

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Ran it on the lake yesterday for the first time. Runs GREAT. I have about 4 hours on it now and have had it up to about 4800 RPM. I checked the high speed timing under load on the trailer, but forgot to confirm that the timing lever was up against the stop. SO I will have to do that again. I have had to check everything two or three times anyway to get it right, so no big deal.

It still wants to idle fast at 2Deg BTDC. Next time I put it in the lake, in forward, I'll see if I can idle it down a little.

Changed the lower unit oil before I went out. Found it was pretty old and a little goopy. So after my 2 hour test run I went ahead and changed it again, hoping that any old oil was mixed up in the new and drained. NO metal chips on the drain plug.

I forgot to take a pic to post! Next time!

 

[papp101]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Man, great job and excellent problem solving.

Between the two motors, have you ensured that your cables are adjusted properly and that all 4 butterfly's on the carbs are closed? Check the butterfly carb sync method if you haven't already using an 1/8th in drill bit. Google carb sync drill bit if you havn't done that before. Should give you a feeling of where you're at. It could be that 1 piston is "pulling" the others to a higher rpm because it's getting more fuel, or worse, air causing a lean running condition.

What happens when you adjust the throttle screw to idle down the motor? or is the "idle stop" what's controlling the timing? not as familiar with outboards as I am with other gas-burners. I'll have to look at my merc.

Check odd-ball things like motor voltage/regulator stuff. Mine wouldn't idle down when my regulator was fried, which could mean you're doing the right thing with your timing adjustment, but there's a voltage draw trying to charge the battery so at low rpm when it wants to cut out, it's not firing the coil packs. Long shot, but something to "drink" about.

Battery fresh and holds good charge? Fuel is somewhat fresh, not trying to break in on last year's gas?

I'll check back!

 

[justchecking]

Re: 91 Mercury 115 Rebuild - Let's see how it goes!

Most of the things you mentioned I took care of. HOWEVER, I am wondering about the regulator. Couple of times I noticed the voltage at 16V which doesn't seem right. Doesn't matter what RPM. That is on my list to check into.
Thanks for the feedback!