1988 mercury 150 xr4 carb cleaning

[jhogue46140]

Re: 1988 mercury 150 xr4 carb cleaning

Ok. I have the boat put back together. Below is what I have done so far.
1.)Carbs cleaned and rebuilt.
2.)Fuel pump rebuilt.
3.)New fuel lines
4.)New trim solenoids

I have also checked the hot foot and made sure the throttle is wide open when it is pressed down all of the way. The carbs do not open all the way when the hot foot is completely depressed. I am not sure I can move the hit foot. I have adjusted the barrell on the throttle cable and it now allows the hot foot to open the throttle completely. Is adjusting the barrell ok to do. Thanks James

 

[j_martin]

Re: 1988 mercury 150 xr4 carb cleaning

Ok. I have the boat put back together. Below is what I have done so far.
1.)Carbs cleaned and rebuilt.
2.)Fuel pump rebuilt.
3.)New fuel lines
4.)New trim solenoids

I have also checked the hot foot and made sure the throttle is wide open when it is pressed down all of the way. The carbs do not open all the way when the hot foot is completely depressed. I am not sure I can move the hit foot. I have adjusted the barrell on the throttle cable and it now allows the hot foot to open the throttle completely. Is adjusting the barrell ok to do. Thanks James

When the hot foot is at idle, the idle stop screw (bottom one on the lever) should hold a calling card under the rubber bumper, but allow it to be pulled out. If it's real tight, you can adjust the cable some more. If it falls out, you have to find out what's keeping the hot foot from fully stroking it. If you leave it loose, the motor will overspeed at idle.

If the cable was that far off, I'd do a link n sync before I launched it again.

hope it helps
John

 

[jhogue46140]

Re: 1988 mercury 150 xr4 carb cleaning

I'm going to do a link N sync on Saturday. Hopefully I will be able to get out on the water Sunday. I was reading the manual and it mentioned adjusting the idle mixture screw. Where do I find this? Thanks Doug

 

[j_martin]

Re: 1988 mercury 150 xr4 carb cleaning

WH carbs don't have any. You set idle by the timing. Link-n-sync procedure sets a base idle timing. You adjust it on the lake for final idle speed.

Be sure you have the right instructions. Different engines will have different timings, throttle cam settings, etc.

On an XR4, there is an advance module that you disconnect during the procedure. WOT timing is set slower than if you don't have an advance module. (19 d as I remember)

Good luck.
John

 

[jhogue46140]

Re: 1988 mercury 150 xr4 carb cleaning

I was guessing that was the case but wanted to make sure. I have a seloc manual. Could I sen dyou a copy of the instructions or post them and would you verify they are correct. Thanks James.

 

[j_martin]

Re: 1988 mercury 150 xr4 carb cleaning

I was guessing that was the case but wanted to make sure. I have a seloc manual. Could I sen dyou a copy of the instructions or post them and would you verify they are correct. Thanks James.

Sure

jm

 

[jhogue46140]

Re: 1988 mercury 150 xr4 carb cleaning

Hi John,
I have pasted the instructions below. Thanks for your help. James

Timing Pointer Adjustment
1. Remove all of the spark plugs.

2. Install a dial indicator into the No. 1 (top) spark plug opening.
Slowly rotate the flywheel CLOCKWISE until the No. 1 piston is at top dead center (TDC).

3. Set the dial indicator at 0.

4. Slowly rotate the flywheel COUNTERCLOCKWISE until the dial indicator needle is approximately 1/4 turn beyond the 0.462 mark.

5. Now, slowly rotate the flywheel back CLOCKWISE until the dial indicator is exactly at 0.462.

6. Adjust the timing pointer until the pointer is aligned with the 0.462 mark on the timing decal.

7. Remove the dial indicator.

8. Install the spark plugs. Primary Pickup Synchronizing Timing
9. Connect a flush device to the lower unit.
NEVER operate the powerhead over 1000 rpm with a flush device attached, because the engine may "RUNAWAY" due to the no load condition on the propeller. A "runaway" engine could be severely damaged.

10. Start the engine.
Water must circulate through the lower unit to the engine any time the engine is run to prevent damage to the water pump in the lower unit. Just five seconds without water will damage the water pump.

11. DISCONNECT the fuel line to the powerhead.

12. Allow the powerhead to run until it shuts down from lack of fuel.

13. If the unit being serviced has an idle stabilizer OR a low speed/high speed spark advance module (small "black box" mounted on top of the air box cover, or on top of the starboard cylinder head), the white/black wire MUST be disconnected from the switch box. Wrap tape around the end of the wire to prevent it from shorting out.
For units without oil injection, the idle stabilizer is mounted on top of the air box cover. For units with oil injection, the idle stabilizer or ignition module is mounted above the star board cylinder head.

14. If the link rod was disassembled, check to be sure it measures 11/16 in. (17.5mm) from elbow to the locknut of the adjustment collar. This distance is measured from the outer side of the link elbow to the surface of the locknut.
To prevent the engine from firing during the timing procedure, remove all the spark plugs EXCEPT the No. 1 plug (top, starboard bank). Ground the disconnected plug wires to the powerhead, somewhere away from the open plug ports.

15. Connect a timing light to the No. 1 spark plug.

16. Remove the throttle cable barrel from the barrel retainer on the cable anchor bracket.

17. Loosen the locknut on the idle stop screw. Adjust the idle stop screw until the bottom edge of the throttle cam is aligned with the edge of the front corner of the throttle stop screw boss.
Do NOT install the throttle cable at this time.

18. With the engine in NEUTRAL, hold the throttle arm so the idle stop screw is against the idle stop, and then crank the engine with the cranking motor.

19. While the engine is being cranked, adjust the throttle primary pickup screw until the specified throttle primary pickup mark on the timing decal is aligned with the timing pointer. See the Specifications in the General Engine and Tune-Up chart for the correct setting.

20. Tighten the locknut to hold the adjustment.

21. Loosen the three carburetor synchronizing screws.

22. Position the throttle lever against the idle stop.

23. With the lever in this position, move the roller arm until the roller just makes contact with the throttle cam. Without moving the roller arm, tighten the three carburetor synchronizing screws to hold the adjustment.
Maximum Advance Timing

24. With the engine in NEUTRAL, move the throttle lever until the maximum spark screw makes contact with the stop.

25. Crank the engine with the cranking motor.

26. Loosen the locknut and adjust the maximum spark screw until the maximum spark advance timing mark is aligned with the timing pointer.
AN EXPLANATION: This adjustment will result in a spark advance reduction of 2? at maximum rpm, due to the spark advance characteristics of this ignition system.

27. Tighten the locknut to hold the adjustment.

28. Remove the timing light.
Throttle Stop Adjustment

29. Move the throttle lever to the wide open throttle (WOT) position.

30. Loosen the locknut and adjust the full throttle stop screw to permit full throttle shutter opening at WOT.

31. Check to be sure the throttle shutters do not act as a throttle stop.

32. Use a feeler gauge and check the clearance between the roller and the throttle cam at WOT. This clearance should be 0.010-0.015 in. (0.25-0.38mm). Tighten the locknut to hold the adjustment.

33. Install the spark plugs. Connect

34. the white/black wire between the idle stabilizer or ignition module and the switch box.
Idle Adjustment

35. Connect a flush device to the lower unit.
NEVER operate the powerhead over 1000 rpm with a flush device attached, because the engine may "RUNAWAY" due to the no load condition on the propeller. A "runaway" engine could be severely damaged.

36. Connect the fuel line to a fuel source.

37. Plug the electrical harness into the engine receptacle.

38. Remove the engine cowling.

39. Connect a tachometer to the engine.
Water must circulate through the lower unit to the engine any time the engine is run to prevent damage to the water pump in the lower unit. Just five seconds without water will damage the water pump.

40. Start the engine and allow it to warm to operating temperature.

41. Remove the cable barrel from the barrel retainer, and loosen the locknut on the idle adjustment screw.

42. Shift the engine into FORWARD gear.

43. Adjust the idle rpm to the proper rpm as listed in the Specifications in the General Engine and Tune-Up chart. Tighten the locknut to hold the adjustment.

44. With the end of the throttle cable connected to the throttle lever, hold the throttle lever against the idle stop. Adjust the throttle cable barrel to slip into the barrel retainer on the cable anchor bracket with a very light preload of throttle lever against the idle stop. Lock the barrel in place.
An excessive preload on the throttle cable will cause difficulty when shifting from FORWARD gear to NEUTRAL.

45. The preload may be easily checked by placing a piece of paper between the idle stop screw and the idle stop, and then withdrawing it. If the paper does not tear, but drag can still be felt, the preload is correct. Adjust the cable barrel, if necessary, to obtain the proper preload just described.

46. Install the powerhead cowling.
If sufficient throttle cable barrel adjustment is not available, a check MUST be made for correct installation of the link rod (located between the throttle lever and the throttle cam). Each end of this link rod must be threaded into its plastic barrel until it bottoms against the throttle lever or the throttle cam casting, and then backed out from this position ONLY far enough to obtain correct orientation of the link rod. The link rod must be backed out LESS than one turn. All timing adjustments must be reset after this procedure has been completed.

47. Disconnect the tachometer and the flush device.

 

[j_martin]

Re: 1988 mercury 150 xr4 carb cleaning

Going from memory, I remember a little different cam adjustment. I think the alignment of the roller cam is 1/8 inch clearance instead of contact.

As I recollect, I timed idle at 11 ATDC, and WOT at 19 BTDC. That gives a final timing of 19 degrees at WOT until 5000 rpm when the module takes it up to 23. Then at 5500 the module takes it back down to 17. (kinda like hitting the wall.)

I'll look to see if the throttle pickup is touching, as your instructions, or 1/8 inch as my feeble mind seems to remember. I'll be back here some time tonight.

Keep track of what's off so we can compare theory to actual performance.

hope it helps.
John

 

[j_martin]

Re: 1988 mercury 150 xr4 carb cleaning

James,
Here's the differences:

17. Loosen the locknut on the idle stop screw. Adjust the idle stop screw until the bottom edge of the throttle cam is aligned with the edge of the front corner of the throttle stop screw boss.
Do NOT install the throttle cable at this time.

On the XR4, the throttle cam lever is angled upward toward the back. This adjustment is to put the aft/lower edge of the throttle cam 1/8 inch from the forward edge of the throttle stop screw boss. (I use a 1/8 inch drill bit as a gauge.)

-------------------------------------

19. While the engine is being cranked, adjust the throttle primary pickup screw until the specified throttle primary pickup mark on the timing decal is aligned with the timing pointer. See the Specifications in the General Engine and Tune-Up chart for the correct setting.

11 degrees ATDC, according to the Murkery manool.

--------------------------------------------------

23. With the lever in this position, move the roller arm until the roller just makes contact with the throttle cam. Without moving the roller arm, tighten the three carburetor synchronizing screws to hold the adjustment.
Maximum Advance Timing

This is accurate, not the spacing I had "remembered".

---------------------------------------

26. Loosen the locknut and adjust the maximum spark screw until the maximum spark advance timing mark is aligned with the timing pointer.
AN EXPLANATION: This adjustment will result in a spark advance reduction of 2? at maximum rpm, due to the spark advance characteristics of this ignition system

18 degrees BTDC, acording to the Manual. Go 23 degrees IF you discard the "advance" module.

Whether or not you use the module is a toss up. If it works, it'll keep it idling under adverse conditions, and mid range timing will be a bit slower and easier on the engine. If it catastrophically fails at WOT, it'll hit you in the back of the head with a rod cap. (Theoretically, I haven't heard a lot of incidents)

----------------------------------------

32. Use a feeler gauge and check the clearance between the roller and the throttle cam at WOT. This clearance should be 0.010-0.015 in. (0.25-0.38mm). Tighten the locknut to hold the adjustment.

This isn't rocket science, and needn't be real precise either. The object is to insure that there is a little free play in the carb linkage so you don't damage carbs when you mash the throttle.

----------------------------------------

46. Install the powerhead cowling.
If sufficient throttle cable barrel adjustment is not available, a check MUST be made for correct installation of the link rod (located between the throttle lever and the throttle cam). Each end of this link rod must be threaded into its plastic barrel until it bottoms against the throttle lever or the throttle cam casting, and then backed out from this position ONLY far enough to obtain correct orientation of the link rod. The link rod must be backed out LESS than one turn. All timing adjustments must be reset after this procedure has been completed.


If you even remotely suspect an ace (spelled with a double s) mechanic has been here, I'd check this link rod as a first step, to avoid repeating all the other steps. On the other hand, maybe you enjoy it so much you want to do it twice.

I'm going back to bed.

hope it helps
John

 

[jhogue46140]

Re: 1988 mercury 150 xr4 carb cleaning

I have everything put back together. I disconnected the hotfoot from the floor and pushed it completely down. The throttle completely opened. When I put the hotfoot back where it was mounted and mashed it down throttle was not completely opened. It was about half way open. I remounted the hot foot where it would get complete range of operation. I then went through the link n sync procedure. Everhthing checked ok. Is it common to not need to make any adjustments when doing a link n sync. I am going to take her out this weekend and see how she does. I am guessing the limit on the speed/rpm and the sluggish hole shot were related to the hotfoot acting as a governor. I cant believe somebody mounted it where it would not allow it to open all the way up. Thanks for all of your help. James

 

[j_martin]

Re: 1988 mercury 150 xr4 carb cleaning

I have everything put back together. I disconnected the hotfoot from the floor and pushed it completely down. The throttle completely opened. When I put the hotfoot back where it was mounted and mashed it down throttle was not completely opened. It was about half way open. I remounted the hot foot where it would get complete range of operation. I then went through the link n sync procedure. Everhthing checked ok. Is it common to not need to make any adjustments when doing a link n sync. I am going to take her out this weekend and see how she does. I am guessing the limit on the speed/rpm and the sluggish hole shot were related to the hotfoot acting as a governor. I cant believe somebody mounted it where it would not allow it to open all the way up. Thanks for all of your help. James

Link n sync adjustments are all locked down and shouldn't change with use. You just proved that the knucklehead that mounted the hotfoot didn't get his meat-hooks too deep into the engine. You needed to know that, however.

Post the results. Don't forget to wear your life vest and use the kill switch.

John

 

[jhogue46140]

Re: 1988 mercury 150 xr4 carb cleaning

Took the boat out today with my son. The lake we went to has a speed limit of 20 mph. However the boat was much more responsive. Hole shot was improved. It took only 5-6 seconds to get on plane. This was with both live wells full and 30 gallons of gas in her. It was taking about 15 seconds before and I had to wait for live wells to empty before getting up to speed. I did push her to about 35 mph for a feww second. RPM was about 3200 and I had a lot of throttle left. I floored it a couple of times while we were cruising around at about 23 mph and could tell she had alot more power.You could feel it push you back in the seat.
I can't believe the hotfoot was mounted where it wouldn't allow wot. It kind of scares me about what else might not be set up correctly. Thanks for all of your help in troubleshooting this. James

 

[j_martin]

Re: 1988 mercury 150 xr4 carb cleaning

If you get the engine mounting and prop setup right, you'll have to worry about neck injury when you blast off.

When I floor mine with a new passenger in the boat, the usual reaction is "Holy *&)(*&_)*&"

John

 

[jhogue46140]

Re: 1988 mercury 150 xr4 carb cleaning

That makes me think of another question. The boat has a hydraulic jack plate on it. At some point the hydraulics must have went out. It is now a manual jack plate bolted in place. How do I determine if the engine is at the correct height? Thanks James

 

[j_martin]

Re: 1988 mercury 150 xr4 carb cleaning

That depends on about everything.

With the motor fully trimmed in, you should get a jump up onto plane in very short order, as the prop will actually be pushing up on the stern.

As you come up to speed, and trim out, the prop should run near the surface, maybe even slightly piercing the surface if it's a 5 blade. It should max out before it gets to full trim unless you carry the bow really high. It should throw a rooster tail about as high as the motor, not much higher. Any more is wasted power. Believe it or not, if the motor is too deep and you compensate by overtrimming, it'll throw a tall roost. Water pressure may begin to fail at full trim out, and it would be normal. Without a low water pickup, the limit on height is usually how high you can carry it and keep water pressure.

The reason for the 5 blade comment above is that these small diameter LU's tend to throw a pinion from torque vibration if they are surfacing a 3 blade prop. Most recommend you keep the prop fully submerged on this motor. I run a high five about 10 percent surfaced. I can trim out about 80% before I begin to lose water pressure.

A trim tab is useless when you run them that high. If steering torque is a problem you need a "torque tamer" mod to the skeg.

I suspect that if you ditch the inoperative jack plate and put on a manual plate, it'll help because of the weight.

Oh yeah, run high perf lube in the LU.

hope it helps
John

 

[Davidsr61]

Re: 1988 mercury 150 xr4 carb cleaning

This would be the same for a 1989 model too?