Help with engine timing please merc 2.5

[tronman]

Hi all, thanks in advace for your input. I am having an issue with timing I believe, contributing to detonation.

I have just finished a rebuild on a 1998 175xr2 (mercury 2.5l sport jet) powerhead. The engine would barley run before and had three pistons/cylinders that were toast.

I had all cyl bored for .030 oversize and the following parts are new

wsm platinum .030 oversize pistons and wrist pin, bearings, rings ect..
steel cage rod bearings
lower main bearing (steal cage)
boyesen carbon fiber reeds
full gaskets
plugs
oil drive gear

additionally, I had the heads machined for higher compression and I am running a 1mm thick head gasket instead of the 1.2mm standard head gasket.

I used a dial indicator and set the needle on the flywheel cover to align with .462 from TDC.. then adjusted the WOT stop @ 22 degrees. ( this was done prior to hooking up fuel and initial start up)

(running at idle)
I had tried to set the primary pickup screw at 0 degrees, but was unable to get anywhere near 0 from what i could tell. I just used a pain marker with 2 seperate colors on the flywheel for 22 and 0 degrees. Maybe I didnt try adjusting enough as it was idling up the engine. Anyway with the timing perfect at WOT and the engine seemily running ok I proceeded to take the boat out for break in.

Ran it for about 30 min on saturday and maybe noticed a pinging at mid rpm

Took it again sunday and after running for a few hour the noise became much worse. I thought i had made an error on the build or some type of mechanical failure. It was very noticble in the mid range, NOT present during low or high rpm.. i pinned it a few times only momentarily and the engine screamed and sounded great.

while running in neutral I went to the powerhead and reved it a little, sounds sluggish and not snappy... Then adjusted the primary pickup on the water just going by what the engine acted like and acheived a snappy rev..

back running again the noise from the engine almost went away completely so i am hoping that the engine is good and i was hearing some racket caused by detonation.

Is this engine good or toast again?
If it where detonation making the noise, why did it show up after an hour of runnig and not earlier on?
Can anyone point me in the right direction for getting the timing right all together instead of just WOT like it is now? I have the manaul but was unable to find 0 degrees, and confused about the racket and it going away with adjusting the primary pickup..

fuel was 93 oct mixed at 32:1, i have bypassed the oil injection by looping the oil back to the engine mounted tank, left it hooked up to keep the motion sensor from alarming the TKS ecm.

http://motorka.org/doc/mercury/service_manual/jet/SJ175XR2_852396r1/1d.pdf (Pgs 19-21 contain the info for timing)

[tronman]

C'mon guys, over 70 views without a single opionated person here? I dont buy that.

Turns out that I had the stator postioned incorrectly. I placed it back where it was when I dissassembled the enigne, just goes to show that you cannot count on prior repair being correct.

Additionally I had marked on the flywheel with two seperate colors for 22 and 0 degrees to make them more visable. I made a mistake marking -10 for what I thought was 0. So no suprise I was unable to find the right mark.

After relocating the stator as pictured in the manual, I re-timed the engine with the TKS ECU dissconnected as I read that it will advance timing 5 degrees when engine temp is below 104. I know have WOT and primary timing perfect as per manual.

Now the biggest question remains, do any of you think I may have caused serious damage to my freshly rebuilt engine by running it with the timing off? I ran prob 25 gallons of fuel through it between saturday evening and sunday. I could hear the detonation "knock" at mid rpm only, and it cleared up after turing the primary pickup out on the water.

I have yet to water test it since getting the timing dialed in.

[TEXAS20225]

what was the compression after rebuild and 25 gallons later is it a carb or efi

[tronman]

It is carborated.
I havent checked compression since prior to rebuild. It is much harder to get to now that it is in the boat but it is do able, id have to remove the coil packs to get to the plugs while laying across the top of the engine.. it sux

I was told by the guys doing my machine work that it would take it to around 145psi per cylinder.. Would you suggest going through the hassle of checking compression before running it again?

[tronman]

I see where you are going with the compression, I should have established a baseline for all 6 cylinders after rebuild, then would have something to gauge where they are at now.

[PanRonnie]

http://boatinfo.no/lib/mercury/manuals/105and140jet-135-150-175-200-225.html#/6

you can print that out also

[PanRonnie]

http://boatinfo.no/lib/mercury/manuals/175xr_sportjet.html#/0

[tronman]

Thank you for the links. I will report back after a water test.

[tronman]

Okay, water tested yesterday and ran around the river for the evening. All is well, it humms smooth at mid range and screams when opened up.. I dont think i ran it long enough with the timing off to damage anything. Now its time for me to enjoy it this weekend:)

[fierodough]

Wow! We had the same problem! 3 cylinders with bad compression. I'm waiting on my pistons to arrive so I can have the block bored 0.030" over. I just bought the Chris Carson "sport reeds" for the 175 XR2.

You mention you installed the stator wrong? How so? and what was the correct way? (Just so I can avoid the same problem) .

I removed EVERYTHING that had to do with oil injection. The only thing remaining is the plastic gear on the crank shaft. I heard it was needed to use up some "volume" in the crank case.

Do you have a wiring schematic for this engine? I would like to go through the wiring to make sure I'm getting everything back together correctly.

thanks! :)

[tronman]

http://motorka.org/doc/mercury/service_manual/jet/SJ175XR2_852396r1/cover.pdf this is the entire manual in PDF.. just go to service manual outline on the left menu, then select which section you are looking for ( electrical, powerhead, pump ect)

There are multiple screw holes around my stator, you are only using 4 to screw that down to the upper end cap. Somehow I changed the orientation of the stator about 45 degrees, it was just rotated furth than it should have been and you can make the screw holes line up in several differnent positions.

I found ONE photo ( igition system, pg 15) in that manual showing the stator exposed and used that to place my stator in the right spot. It makes sense bc the tirgger has a set gap that it can move in to effect timing, rotate the stator and it changes the area where the trigger moves in relation to the stator?

I replaced the oil drive gear as well but I have it the external oil tank removed and the pump is just circulating back to the engine mounted resivor. I wanted to make sure that I could dissconnect the motion sensor without alarming b4 buying the block off plate. I havent done this yet, do you know if it will alarm when the sensor is unplugged?

[fierodough]

it will alarm if the sensor is simply unplugged. If you remove the alarm box, it will no longer alarm but your overheat horn will still work. That is what I did. My oil pump bearing had seized causing the plastic gear to strip and the cog gear to chip. It was a real mess in there... I did not want that to happen again. I ripped everything out and I'm getting a local vinyl sign shop to make me a sticker for my gas cap, above the gas cap and on the flywheel to remind me or anyone using the boat to premix 40:1. To break in the engine, I would run even more oil... My manual recommends a premix in the tank PLUS the oil injection system for the break in period.. I think I will run 25 or 30:1 for my first tank. It also says not to do any WOT runs for the first 2 hours. and for the next 5 or so hours to only do short WOT runs.

I understand that on a newly rebuilt engine that is still doing the break in, that the compression will be lower.. Around 90PSI... then it will climb to the 140-150 range.. as the rings wear to the cylinders. (I hope...)

[tronman]

The alarm box being the TKS ecm? I know that it will run without it, but doesent it control the enrichment solinoid for cold starts (instead of a choke) and advancing timing during cold start? I suppose one option would be to cut out the alarm horn,, lol that would do it for sure. I do not plan to leave that plauged oil set up running much longer, i do not want to give it the oppertunity to shred in my brand new enigne..

Yes i read the same for pre mix 50:1 plus auto oil for break-in.. i myself have just been premixing 32:1...

Im wishing I would have run my eninge a little harder earlier on after reading some info on breaking in engines.. most say varied rpm and just giving them hell (after a thourough warm up)

http://www.mototuneusa.com/break_in_secrets.htm

[fierodough]

You remove the TKS box and wire the purple wire straight to the enrichment solenoid (or something similar to this, I have it saved at home).

I don't think you really want to give the engine hell, at least not early on in the break in. I coworker here rebuilds Harley engines...He told me that if you can see how red hot the rings get on an engine that is doing a break-in you wouldn't even want to idle it. :)

I’m looking over the wiring diagram you sent me the link to (thank you by the way!). I’m trying to find a good feed to wire an hours meter to the engine. Something that is only hot when the engine is actually running.. Not just the ignition.

Cheers!

[fierodough]

Aha! found the info for removing the alarm!


remove the "TKS" and wire the enrichener direct to the ignition switch push to
choke function. and take the electric fuel pump and wire it also to the push to
choke wire. the over heat alarm is set by a normally open temperature sensor
switch that activates the ground circut of the alarm modual under the dash. you
will not have the beep beep at key on but rest assured if the tan/blue wire is
attached to the alarm modual it will sound if it gets hot...

[tronman]

Cool, thanks for the info. I am not sure of a wire with voltage that isnt ignition related, maybe the grey wire that goes to the tach?? you could verify with a mulitmeter and just see how much voltage is on the grey wire with the engine off, idle and above.. Ive never used an hour meter so Im not sure how much voltage they need to count up..

For the temp stuff, im glad you tunned into the thread. I actually came up confused with that part of the wiring when i assembled my engine.. the diagram only shows one thermal sensor.

I have somthing on starboard side head with..
ground to the head
tan/blk to tan/blk on harness
tan/blk to blk on harness
tan/blu that is currently open ( I had this wire hooked to the tan/blu on harness and the overheat alarm stayed on unplugged,, engine was not even started yet)

And the port side head has a sensor
ground to head
tan/dark blu that is also open.... I only had one wire left on the harness and that was the tan/blu wire that alarmed when hooked up to the starboard sensor.

Any chance you could check yours out and let me know what is correct? I have a solid tan "jumper wire" that was left over after i finished :confused:

[fierodough]

Tan/blu I think is the overheat horn. When it is shorted to ground, it will alarm. So my guess is you want both temp sensors wired in parallel to that tan/blu wire so if one of them shorts to ground (temp threshold on the sensor is reached) the horn will sound. This is good in case one head gets clogged and is not cooling properly.