87 xr2 fresh rebuild need help

[ckhuber]

Ok Maybe someone can help me with this.
I have an 87 Mercury XR2.
I bought this motor knowing it needed rebuilt so I did that. Rebuilt entire fuel system and Followed all break in procedures. So when at idle it runs fine. Above 2500 rpm this thing screams. But from idle to 2500 bogs and acts like its missing?
All plugs have spark at idle and I assume above 2500. It is now premix and doesn't have the advance module.
I am running this on a 93 searay bowrider with a 4 blade 20 pitch aluminum prop.
Please help me solve the mystery I am new to this but have all the tools I think I will need dvo meter,timing light and such.
Also I cannot check timing because the motor did not come with the timing cover so if anyone has a spare I would be willing to purchase.

[sschefer]

One of the pro's may be able to nail your problem down to something specific from the info you provided, I can't.

I do understand that fuel and timing go hand in hand on these engines and if its not pretty darn close to perfect you might experience problems like your having.

I would make a pointer from a piece of welding rod and attach it to a nearby bolt. Then I would set the pointer to zero using the proper method and time the engine in accordance to what the pro's here tell you for your engine with the spark advance module removed.

The other mechanical area I would look at is accellerator pumps but you might just cure that when you perform a full link and sync.

Following that and if the problem persists, you may have too much prop for a decent hole shot. You could try a vented prop that will slip a little more at low RPM's.

What I would not do is run the engine until after you set the timing. From what I've read, bad timining or timing issues seem to be the # 1 engine killer.

[ckhuber]

Thanks for the advice I need to get this thing timed and you had a good suggestion I will try I will let you know Thanks again

[transomstand]

Also I cannot check timing because the motor did not come with the timing cover so if anyone has a spare I would be willing to purchase.

Do not run the engine until you can set timing, a lot of your work can go up in smoke. You need to do the timing and syncronization procedure.

[wrechin2]

I agee, do not run untill timing is verified. Doing the link and sync will ensure it didn't blow because of timing. Remove the idle stabilizer and set to 24*. I fought with one and thought it was electrical. I tested the WHOLE sytem and it tested good. Have had stuff test good and be bad so I replaced the whole igniton system with a known good one, because it was missing on take off. It turned out to be a stuck bleeder valve loading up 1 cylinder on take off. I have also had triggers that had a broken wire and as the timing arm would move, it would make connection and all cylinders would then fire. I have also had a stator that after 3K would loose spark on 1 and I would have bet a million dollars that a stator couldn't do it. I would have lost. Since then, I have had 2 others doing it. 1 was doing it at a idle. So there are multiple possibilities.

Simple and quick test that will help us help you is take a timing light and put on EACH cylinder to verify that you aren't loosing spark when it is happening. Also pull the rubber covers back on the coils and make sure you don't have a bunch of cracked magnets. This will drop voltages as now it has multiple magnetic fields. I had one that had 5 cracked magnets. The engine picked up 400 rpms from the replacement of the coils. Hope this helps

[ckhuber]

Thanks to everyone I will try all the advice hopefully get to it this weekend and let everyone know the outcome

[wrechin2]

NO PROBLEM!!! Just keep us up to date.

[Way2slow on H2O]

:iagree: Like Wrenchin mentioned, check the recerk hoses AND check valves 1st. That's the #1 problem for crappy off idle sluggishness :thumbsup: (you mentioned it runs good above 2500 "screams")

The timing is a good thing to check, especially if you're running anything higher than 120 psi compression and less than 91 octane fuel.

[grendle]

Should you keep the primary timing (at idle) at 11 deg. without the module?

The timing marks on my flywheel only go to 22 deg on the highend as well (which is where I keep it, hoping to stay safe) But other than a hard start condition after sitting recently mine has been running well. Thanks to you guys!

[wrechin2]

With the module removed, I like 0* to 4* ATDC, but the engine will determine what it wants. The closer you are to 0* the easier it will start (most of the time). MOST have a spec of 0* to 9* ATDC. If the idle is too high go more ATDC. JMO.....

[transomstand]

Should you keep the primary timing (at idle) at 11 deg. without the module?

The timing marks on my flywheel only go to 22 deg on the highend as well (which is where I keep it, hoping to stay safe) But other than a hard start condition after sitting recently mine has been running well. Thanks to you guys!

I keep my total advance at 22° to play it safe as well. Idle timing is less specific, it's kind of whatever the motor wants to achieve good idle speed and quality. I don't even know what my primary timing is, after link and sync, I simply adjust idle speed with the primary pickup screw.

[sschefer]

I keep my total advance at 22° to play it safe as well. Idle timing is less specific, it's kind of whatever the motor wants to achieve good idle speed and quality. I don't even know what my primary timing is, after link and sync, I simply adjust idle speed with the primary pickup screw.
:iagree:

Regarding starting, you can keep your initial timing at whatever makes the motor idle best and when starting just give it a little throttle and this will add the advance you might need to make it start a little easier.