1990 XR4 black Max

[clevecan]

Can someone tell me if my 1990 model 150 XR4 Black Max is a 2.0 or a 2.4 Liter? I'm not sure and would like to know.
I,ve been told it was a 2.4 and I was told it was the same as the 200 just I guess smaller reeds and carbs.

 

[Faztbullet]

Re: 1990 XR4 black Max

It is a steel sleeved 2.4 block and difference is carbs ,crankcase cover,intake and exhaust port timing. Yours has vertical reeds where a 200 has horizontal..puts out around 165 hp at prop Max rpm is 5000-5600 anything over that is wasted as torque/power curve start to fall as engine runs out of breathing(air flow).

 

[clevecan]

Re: 1990 XR4 black Max

Ok thanks for all the info, I have it on my ranger bass boat and it runs great. I ran it at WOT the other day and it was turning 5900 almost 6000 if trimed out/
running a merc 21 pitch three blade do you think I need a tad more prop?

 

[j_martin]

Re: 1990 XR4 black Max

Ok thanks for all the info, I have it on my ranger bass boat and it runs great. I ran it at WOT the other day and it was turning 5900 almost 6000 if trimed out/
running a merc 21 pitch three blade do you think I need a tad more prop?

Driver only, empty live wells, that's just about perfect. It'll load down when yer hauling freight. Measure your prop hub before you buy anything. It could be either 4" (usually quoted as V4 size) or 4 1/2" (Normal Merc V6 size). Engine came with a smaller LU, but the bigger ones will fit, are tougher, and cheaper, so they get changed out when trouble comes.

On my 88 Tracker FS1800 I run a 24 pitch high five for fishing, (Stability is more important to me than absolute top end) and I go down to a 22 for pulling skiers, tubes, or if my fishing partner is grossly obese. My engine feels best at right around 6000 rpm WOT. It purrs along very nicely at 3500 - 4000 rpm. Any slower and the boat starts dropping in and getting inefficient. High five hole shot is like a sling shot.

 

[clevecan]

Re: 1990 XR4 black Max

Well that was with just me and two 3/4 tanks of fuel I have two 18 gal. tanks and full turny load.livewells full. never really looked at speedo just RPM's
Not the fastest holeshot but not bad, I know a 4 blade would give me a better holeshot just making sure 5900 to 6 grand was not turning
it to fast. never have tryed a high five but see them on some boats. I think the lower unit is a 4" but the motor seems to be in great shape
i,ve had no problems with it.

 

[j_martin]

Re: 1990 XR4 black Max

The XR4 comes from the factory with an "advance" module on it. It advances the timing a bit at 5000 rpm, then retards it at 5500 rpm, causing the torque curve to effectively hit the wall.

It's enough of a source of trouble and not enough of a benefit for Mercury to stock them for replacement. If you take it off, and advance your initial timing from 19? to 23?, you get a pretty smooth torque curve into the low 6's before lack of air through the vertical reeds strangles it. That may have already been done with your motor.

I think proper prop ventilation with exhaust allowing the engine to spin up into the torque band is more important than blade count. One advantage of the high five is that if you surface it, there's always 3 blades in the water, damping the torsional vibration that likes to put the pinion out the side of a 4" gear case. The other one is that it has extreme traction at mid speeds, even if it's breaking the surface. You usually see them on ski boats or footin' boats.

 

[clevecan]

Re: 1990 XR4 black Max

Sounds as if you have these Mercurys down,Thanks for info on them. I'm not sure if anyone has removed the advance module, I bought the boat
from a X basket ball player with the houston rockets Matthew Bullard so maybe Ranger made some mods but really dout it. I think i'll run it as is
being i'm not trying to get it faster just making sure I can keep it happy and alive.I hope to have it last me for years to come, again thanks for
all the info.