mercury 150 xr6- more questions

[jbjennings]

Guys,
I took one look under the cowl on my friends new motor and got the impression that it is way out of my league. If it was mine, I would probably get a book and rebuild the 3 carbs and link and sync 'em like suggested, but it not being mine and worth more than all my motors and boats put together, I don't want any part of it. I would be willing to put a new water pump on it since it is 9yrs. old and I think I can handle that with no problem if you guys say there aren't any unusual things with those big 'ol things. I did run it again for a short time today and have some info on it. It's lowest idle in gear is 700 rpm's on the tach which felt perfect. Out of gear is about 1100 rpm's. It idles fine with no coughs and cranks up fairly easily cold, instantly warm. Is this normal? I have to really snap the shifter fast not to grind into gear which I know is hard on the clutch dog and gear ears. Once again, this is the first fast boat I've ran so maybe, it's supposed to be that way.
Next--- the speedo isn't working. With just a quick glance it appeared that the tube to the pitot for it goes into the motor midsection which has an opening to the water. Is this actually it? Could it just be obstructed and can I disconnect the tube and try to blow it out, or is it most likely the guage itself?
Finally, it has an aftermarket Powertech stainless prop on it that appears to be raked somewhat, going about 3/4 of an inch past the edge of the trim tab zinc anode, which is actually absent the tab. It pulls a little. Can I get one of those half tabs that will help this or cure it? Do you guys need a pic to tell for sure?
Last of all, should I post these problems on separate threads, or what is the correct procedure for multiple questions, I don't want to bother anyone with a long post like this.
Thanks,
JBJ

 

[j_martin]

Re: mercury 150 xr6- more questions

It's a plain jane 2 cycle motor, just pretty big, that's all. Like all 2 cycles it goes squish, bang. If it gets fuel, spark at the right time, and has compression, it will fire.

This motor burns millions of BTU/hour in fuel. A good cooling system is critical. It's recommended that water pump maintenance be considered an annual item. I'd add fuel pump rebuild ($20.00 kit) to that, because a lean condition at WOT can take this motor out in seconds.

There is specific procedure, both in removal and reinstall of the LU, and in water pump repair. Some isn't obvious, so get the book.

Idle sounds perfect. You need to "smartly" shift that motor. It doesn't hurt the dogs to bang into gear as long as the idle is below 1000 rpm. The prop hub absorbs the shock. It does take the goody out of them fairly quickly if you rattle them into gear.

If idle wanders, disconnect the little timing module on top of the motor (3 wires) and reset the idle. If it's unsteady after that, you have carb, reed, or compression problems.

The idle stabilizer/timing advance module is noted for being flakey. The disconnect and ignore procedure is so common that Murkery doesn't even stock them anymore. If you do that, reset your max timing to 23 degrees. You may notice a pretty good pickup in the hole shot, especially if your propeller lets it spool up a bit before it bites. (ventilated, for instance)

The speedometer pickup is a little hole on the front of the motor. You're lucky if it's within 20 percent anyway. I'd go GPS for speed, especially if you have to watch a limit for the water-cops.

The motor normally doesn't have a trim tab, because it is normally run very near the surface, and it wouldn't be in the water anyway. Also, the pull goes from one side to the other as it is trimmed out after the hole shot. I think there is a slight bit of torque tamer built into trailing edge of the skeg. Additional correction can be added at that edge. BTW, dual cable rack steering is considered minimum on this motor. I use Morse NFB and have no issues. If it has single cable, or drum steering on it, It's a hazard. If it has single cable drum steering on it, it's suicidal. Just a small amount of slop in the steering can set up a dangerous chine walk pretty easily.

It's a pretty snappy motor, mostly marketed to the fast bass folks. I have an XR4, and I love it.

hope it helps
John

 

[jbjennings]

Re: mercury 150 xr6- more questions

thanks John,
I'd just like to get the speedo working just to have it all working right,I don't care if it's accurate.
That thing is a rocket ship to me. It makes my eyelids flap and drys my eyes out when I go wide open--and I wear glasses.
I'm going to go ahead and get a book so I can see what you're talking about on the idle. I really don't care to learn too much about these things if you know what I mean.
Thanks,
JBJ

 

[j_martin]

Re: mercury 150 xr6- more questions

thanks John,
I'd just like to get the speedo working just to have it all working right,I don't care if it's accurate.
That thing is a rocket ship to me. It makes my eyelids flap and drys my eyes out when I go wide open--and I wear glasses.
I'm going to go ahead and get a book so I can see what you're talking about on the idle. I really don't care to learn too much about these things if you know what I mean.
Thanks,
JBJ

The hole in the front of the foot goes to a hose that comes out in the front, low on the mid going upward. That goes through the hull somewhere and goes to the speedometer, which is just a pressure gauge. There's usually a plastic splice connection so you can take the lower off. You can check it all out with low pressure air.

It's worthwhile to understand your motor, just to compensate for all the jackass "mechanics" out there. I really wonder if some of those birds can even read. Mistakes on a motor that runs as wild as that one can be costly quickly.

Sneak up on learning to drive it. It hurts when you try to go through a gunwale in a hook turn at WOT.

hope it helps
John

 

[RIK ANDERSON]

Re: mercury 150 xr6- more questions

The speedo tube exits the front of the engine just above the gearcase and is held in place with a small piece of rubber and a tie wrap. You have to cut the tie wrap, slide the rubber tube off(it may be split). On my XR-6 there is a small brass fitting that looks like a coupling of some sort. You squeeze the fitting end to end and you can pull the tube loose. You simply push it back in the reattach it. I found out the hard way last week how to take the tube apart. No mention of it in the merc. service manual.

I was replacing my water pump impeller. I also have a question. I've been told that the XR-^ 150 won't pee water out the tell tale until the power head reaches 142 degerees approximately. At that time the t-stats open and relief happens. Is this so or should I have water coming out at start-up?

Thanks ahead of time.

 

[j_martin]

Re: mercury 150 xr6- more questions

The telltale samples the stream of water that flows from the t-stats to the base. It will not pee until it's warm. The most useful part of that is that when you start cold in the morning, look around at the telltale. When the stream comes, it's warm enough to do a hole shot without sticking a piston.

hope it helps
John