XR6 150 Need ideas

[Todd]

While this is not my pleasure boat, I spend a lot of time fishing in it. It is a 18'6" Xpress aluminum with a XR6 150 Mercury.

No matter what I do, I can't get any speed out of this rig. Currently running on a 6" plate with a 25" Laser II. Will turn 5500 RPMs with the 25 and speed of 56 MPH.

Is this top end for the Boat?

[Ray Neudecker]

The boat is capable of much more. I have done several which are running in the 70's. They were all Yamaha 150's however. Replacing the tuner with a stock 200 tuner will help a lot.A six inch setback is another big help. the 25 Pro series Yamaha prop has been the fastest,However the 23 has been the best overall on some. Hope this helps.

[Todd]

Ray,

Thanks for the info on the tuner. Could I ask what RPMs you were seeing with your boat running in the 70's?

I have a 25" Yamaha that I have tried on the boat before. I didn't get anything extra. I also put a 23" on and gained another 250 RPM but no more speed.

[Greg Moss]

Beside changing the tuner see if you can find a set of carbs from a 200 and install some boyeson reeds then hang on. The big restiction is the carb the XR6 has such a small bore in the carb and the long tuner is good for the hole shot with the small carbs. changing to the 200 carbs and the reeds and the 200 tuner will increase the power bigtime.

[jimmyb]

changing to 200 carbs will allow more air in, but really wont give you as much power as a 200 (there are siginificant porting differences between the 150 and 200). Plus with the 200 carbs you are gonna have to play with jetting, cause they are gonna be very rich.

something is terribly wrong with your setup if you are spinning 5500 with a 25" prop @56 mph... you have a ton of slip! I would try playing with the motor height/setback/prop cause there is something definately wrong.



[Edited by jimmyb on 05-03-2001 at 07:02 AM]

[Todd]

It's gonna be a busy weekend. I'll play with the height / prop first. I have a set of 200 tuners and carbs from a 2.4.

Thanks

[Ray Neudecker]

They were turning about 6400.That is the Yamaha Pro Series Pro,not the Lasers. The Yamaha's had non stock reeds and carbs, no other modifications. You need to work with your height some. I never measured anything, just moved it until it worked.

[jimmyb]

todd check out this site: it has a bunch of guys with your boat and motor on it. You can email the owners and get some tips from them.

http://www.bassboatcentral.com/xpress.htm

[MERCMAN]

guys what gives? a merc xr6 has the same bore size as a 2.5 200 with different jetting. this is not the 135 2.0 litre where talking about here. its a 2.5 litre xr6. it has the big carbs! as for the tuner that motor most likely has the old style 2.0 long skinny tuner in it. so anything you do is going to be better than that! dont put 2.4 carbs on that motor unless you know which ones they are unless you want to burn it up! the carbs you have are better than any 2.4 carbs you could get. the 2.4 tuner however would be nicer.not trying to step on anyones toes here so dont get offended.

[Greg Moss]

Mercman your not stepping on toes but you need to look at the carbs on an xr-6 they have less than a 1" bore the carbs from a 200 will wake that motor up. you are right about the tuner it is a long straight one about 18" long with no taper to it at all. I change the carbs and tuner on one on a Champion bass boat it picked up so much power it went up 4" in pitch. I also had installed boyeson reeds. woke it up big time. they have that motor detuned so much it supprising it will run as good as they do. the reeds carbs and tuner from a 200 works. Greg

[MERCMAN]

greg , i have 3 xr6 and one merc 135 of late vintage as well as a few sets of 200 2.5 carbs. all of the xr6 and 200 carbs are the same bore size with different jetting. i am not sure as to the regular 150 but the xr6 has the same bore single float wmh carb as the 200. look it up in the book as well. diffrent jetting. unless someone swiped your guys carbs and replaced them with something else. if you look at your parts book you will notice that the 200 , 175 and 150 xr6 where all offered with the same part #'s on the carbs. once again memory is not fresh at the moment on the standard 150 2.5 but the xr6 does have the larger carbs with different jetting.i am looking at a set of wmh 30's at the moment which where offered on ser # do82000 - g303045 of the xr6-175 and 200 in the book. check it out and get back with us. when they changed to the newer part numbers its not so easy to understand but the carbs are still larger.

[Greg Moss]

ok I checked the casting number on the carbs flange is 3314-821688 they are WHM s the have a bore or 7/8" they are the carb that comes stock on the XR6.I don't know what you have but the carbs that I have came off a motor that no one has touched since it was made so I know for a fact they came that way.

[MERCMAN]

todd please give me the ser # off your motor so i can find out what carb you have on your motor. greg , the carb you have , what is the wmh number on the port side of the carb(i.e. wmh 20-21-25-30?). the number up top is referencing towards the d082000-g303045 serial numbers in which i have a set of 135 carbs with the full throat in them as well as the xr6 unitsand the 175/200 carbs. so your carbs dont make any sense(to me that is). the same part # with the xr6 carbs is the same throat size as well. i am really interested in knowing the wmh number on the side as to why these might be smaller.i still will not recommend for todd to replace his carbs with any 2.4 carbs because they run leaner in the mid(with the exception of the wh-22).i think he already has what he needs.

[Bob T.]

Todd, nobodys mentioned this ,but do you carry alot of heavy gear?Is it placed properly in the boat?Can an aluminum boat have a 'hook'in the hull?Just wonder'n BT

[Greg Moss]

These carbs are Wmh25s. John I bought the carbs for this motor from you. There is a definent difference in size. Mercury changes things so much that there is from one model to the next. But I have seen several XR6s and they have the same carbs on them. There is a bass boat club here that I work on all their boats and a coulpe of them have XR6s And none of them will run with the one I did the changes to. I know the XR6 has a blow down channel cut above the exhaust port but this doesn't seem to affect it. I have to look but I think the stock 150s are all 2.0 liters, I will have to check when I get time to see if they made any that were 2.5s but I don't think they did. I wouldn't recomend the 2.4 carbs either the linkages are different and they are harder to tune. Greg

[Todd]

The motor is a 99' XR6 150. Serial number 06883381.


I did some motor height adjustments this weekend and ended up with a lower setting. The pad on this boat is not flat but has some v in it.

The boat is loaded down, 30 gallon gas, 3 gallon oil, 3 batteries, my big rear .....

It comes out of the hole great but just doesn't have the top end.

[Edited by Todd on 05-10-2001 at 12:12 PM]

[MERCMAN]

i know the 2.0 litre had smaller carbs but i havent seen any of these mystery carbs floating around yet. i will give you a bore measurement on these but like i said they are the same as the 200 carbs. obviously i sold you a pair! what year motors are these xr6's you are working on?

[stan merck]

i think the first one or two years of the xr6 had the smaller bore carbs, the later ones had the same bore size as the 200 carbs. i got a set of 1995 xr6 carbs and they are the same sizes as 200's. hope this helps guys.

[Todd]

Should I change the tuners? I have a set off a 2.4.

[MERCMAN]

todd , the tuner in that motor is terrible. the 2.4 tuner you have is alot better than the one that is in it now.please make sure you have posted all the info that has been done to your rig. the rpms do seem a little low for what your running. you might try a compression check as well. just out of curiousity?