1991 merc 150 xr4

[gregr1971]

i just got a xr4, 91 model, 120-125psi on all 6, i picked it up for 675.00(i think i got a good deal), put on the stand and runs great. (I am new to these mercurys).
My questions are:
What kind of issues do these engines have? anything to look out for??
How will it perform compared to my old 1983 merc 200? (it threw a rod fist time out).
How reliable are they?
What makes the xr4 different from the standard V150?
Thanks,Greg

[gregr1971]

also, what will this do for the performance of this engine??
http://cgi.ebay.com/ebaymotors/_Boat-Parts-Accessories-Gear__Mercury-XR4-XR6-150hp-Performance-reed-valves_W0QQitemZ110192720650QQadnZBoatQ20PartsQ2cQ20AccessoriesQ20Q26Q20GearQQadiZ2823QQcmdZViewItem ?_trksid=p3756.m20.l1116

[mach351]

xr4's were steel sleeved - good candidate for a buildup IMO:thumbsup:

[j_martin]

XR4 is steel sleeved, vertical reed 2.4, noted to be quite stout, probably about 160 hp right out of the crate.

The LU is smaller than most Merc V6's. Gear ratio is 1.78:1.

It's a dandy bass bote motor for the late 80's boats. The vertical reeds limit it's breathing a bit. Shaving the heads could give you a bit more torque. Probably not much else worth doing on it. If you get it to run real good, it'll probably put the pinion out the side anyway.

I think you stole it.

John

[larrysmith]

check all little rubber hoses.
I burnt a piston 2 hours after compleat rebuild because a little hose feeding fuel inricher valve split and drained one float bowl

[gregr1971]

i have been reading on here for hours on the search i did for "XR4", i have a large gearcase on my 200 with the bobs low water pick up, and i do surface the prop when going over oyster reefs, so thats not an issue, easy swap, what is up with the reeds?? my front half on the 200 has a big hole in it , so i cant make that swap!
this motor was on a champion bass boat that supposedly ran in the upper 60's, is it possible??

[gregr1971]

Thanks LS, where can i get the cool looking yellow hoses?? are they better than the black factory ones? (10% ethanol is here now)


check all little rubber hoses.
I burnt a piston 2 hours after compleat rebuild because a little hose feeding fuel inricher valve split and drained one float bowl

[gregr1971]

what is the "fat block" that i have been reading about?

[tlwjkw]

Thats what your motor is. Its a 2.5 block design, horzinal reed with 2.4 sleeves.............

[Jay Smith]

Those engines also were fitted with a 2:1 gear ratio as well as a 1:78 ;)

Jay

[T-REX]

Mercury built tha fatblocks juss to screw wit everbody'z hed!!!....

[apdcop7106]

XR4 has steel sleeves

[mach351]

Yellow line is called Tygon - do a search and you'll find all the info on sizes and where to buy it.

[Jay Smith]

I buy my Tygon from McMasters-Carr best price I've found BUT I buy in bulk
( 100' rolls ) but they( McMasters) do offer in smaller quanities..Pt Number is 5552K23 in the McMaster Cat.

Good luck,
Jay

[gregr1971]

i beleive my 200 lower is a 2:1, is that the better gear ratio? or is the 1.78 the better?

[j_martin]

i have been reading on here for hours on the search i did for "XR4", i have a large gearcase on my 200 with the bobs low water pick up, and i do surface the prop when going over oyster reefs, so thats not an issue, easy swap, what is up with the reeds?? my front half on the 200 has a big hole in it , so i cant make that swap!
this motor was on a champion bass boat that supposedly ran in the upper 60's, is it possible??

Mine's on an 88 tracker 18' bass barge. Am rebuilding the transom and wet floor. ran in the mid 60's wet, hauling 2 group 27 and one group 24 batteries.

Ya dey go, you betcha.

John

[j_martin]

i beleive my 200 lower is a 2:1, is that the better gear ratio? or is the 1.78 the better?

It depends on what you want to do. My 1.78 twists the tallest high-five I can buy for it just about right. 2.0 would make me go get a different prop.

John

[David]

XR2 came with 2:1 only, big gearcase
XR4 came with 1.78 only, small gearcase
XR6 was available with either the 1.78 small or 1.87 large

If you are trying for speed on a light boat, like my SS2000, the 1.78 case is faster, at least until it blows up. Smaller size = less drag, and lower numerical gears make it easier to prop for speed. The small gearcase is marginal for XR4 power, especially when surfaced. Maybe it's just marginal for surfacing. I've blown up 3 of them.

John Tiger told me a long time ago that the big case was better for bow lift.

[gregr1971]

how can i tell if i have the "better" pinion bearing? i do have the small case.

Also, will this work in place of my water cooled regulator, that is not charging, and the stupid thing is 500.00!!!!
http://cgi.ebay.com/ebaymotors/Parts-Accessories_Boat-Parts-Accessories-Gear__MERCURY-OUTBOARD-MOTOR-VOLTAGE-REGULATOR-16-OR-40-AMP_W0QQitemZ320097621070QQddnZPartsQ20Q26Q20AccessoriesQQadnZBoatQ20PartsQ2cQ20AccessoriesQ20Q26Q20 GearQQddiZ2811QQadiZ2823QQcmdZViewItem?_trksid=p3756.m20.l1116

[gregr1971]

David, it will be surfacing with a 17p prop with lots of cup.
my other lower (large case) has 2:1, and a 19p, the boat is 1500-1700lb fully loaded, it is a tunnel hull shallow water boat.

[larrysmith]

I need drive shaft for 1986 150hp black max anybody have good used one?
many parts dealers have told me it is obsolete.
I put a used 1988 lower small hub this spring and blew it up 2 days later it still has a good drive shaft but it won't work on my larg lower.
I twisted my shaft intwo hot boat weekend hardydam mich 2 years ago.
My Black Max is not stocK