Merc 150 Black Max XR4 - Need Some Advice! (Update)

[achilles555]

Hi guys. Here's my situation. I just picked up a 21' 1985 Charger Bass Boat with a 1988 Mercury Black Max XR4 on it (paid $1500 for boat and motor). FYI - the motor's serial number is OB361965. The boat has been sitting uncovered and unused for 7 years. Just before it was parked it had a new lower unit put on it. From what I can get out of the guy that sold it to me, it sounds like the boat was just ran and parked. No maintenance or winterizing...nothin'. I took it to a good Mercury mechanic, and the compression looks good (anywhere from 108 to 112 on all six cylinders). Only 3 of the cylinders were firing though, so I have ordered a new switch box. Hopefully that will take care of the spark problem.

My question to you guys is this...What should I do to this motor before I use it. The fact that it has been sitting for so long with no maintenance scares me a little (actually a lot). I am brand-new to outboard motors, so forgive me for being such a rookie. From looking through these forums, here's what I'm planning to do so far:

1. New water pump kit. (Should I replace the impeller, or the whole thing)?
2. New plugs and wires.
3. New gas line from tank to motor.
4. New gas pump kit. (Is this really necessary?)

What else should I be looking for or doing to get this motor up and running. Also, I am sorta mechanically inclined, and am going to try and do everything myself. Is the water pump/fuel pump a difficult job, or is there anything special I should be aware of? I have a Seloc manual on the way. Hopefully that will help me get through all of this. Any help you guys could give would be very much appreciated.

Just a side note: This boat needs a lot of cosmetic help, too. I spent the day grinding old carpet and glue off of several compartment doors. My hand is still vibrating and my arm is sore as a son of a @%#A&! Can't wait to get her out on the water!

 

[Chris1956]

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

You do need the new waterpump impeller, gaskets and wearplate. Inspect the balance of the waterpump components and replace them if they are worn out.
Change the gear oil. If it has water in it, you have some issues. Obviously hit the grease fittings and put in fresh gas and fresh oil in the oil tank. If the motor was run and parked, the carbs may be clogged with varrnish. I would try to start it up and see if it idles well. if not, you will need to clean and rebuild the carbs.

The wires, coils and other electronic devices I would leave alone until they test as defective.

 

[Windykid]

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

Since the compression could be better, I recommend running some seafoam, and deep creep, hopefully that will restore the compression and clean carbs.
definately change impellar and lower unit lube.

 

[j_martin]

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

Three cylinders on one side could either be a switchbox or a stator. Do the voltage tests before you buy parts.

The XR4 is an amazing motor. It's a little light for a 21 foot bass bote, though. The Lower unit, if stock, can't stand up to surfacing the prop, but properly serviced will do well otherwise.

I bought an old bass bote with an XR4 on it. Biggest issue I have with it is the transom aparrently got wet, and now needs replacement. Big job. I'd check into the integrity of the hull before I put much effort or money into it.

hope it helps
John

 

[achilles555]

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

Thanks for all the help, guys.

j_martin: i had another guy tell me the same thing. That the motor is a little light for the boat. The guy I bought it from also told me it has a hard time planing, and recommended a new prop with a different pitch. It has a 21 on it now. Do I need a different pitch?

The transom and foundation of the boat are in great condition. These Chargers were built like brick s%#@houses, but the boat is heavy.

Am I wasting my time here with this boat and motor? I don't want a boat that won't plane. I'll be using it in a relatively large lake, but a lake that has a lot of structure. I don't care about speed. I just want to be able to get around the lake easily. I'd also like to occasionally pull the wife and kids around on a tube or skiis.

 

[wilde1j]

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

I would also rebuild the poppet valve.

 

[j_martin]

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

Thanks for all the help, guys.

j_martin: i had another guy tell me the same thing. That the motor is a little light for the boat. The guy I bought it from also told me it has a hard time planing, and recommended a new prop with a different pitch. It has a 21 on it now. Do I need a different pitch?

The transom and foundation of the boat are in great condition. These Chargers were built like brick s%#@houses, but the boat is heavy.

Am I wasting my time here with this boat and motor? I don't want a boat that won't plane. I'll be using it in a relatively large lake, but a lake that has a lot of structure. I don't care about speed. I just want to be able to get around the lake easily. I'd also like to occasionally pull the wife and kids around on a tube or skiis.

On an 18 foot bass bote, (Tracker 1800FS) mine does low 60 with me and the fishing tackle. I've got a 24 inch high five on it. When I got it, it did mid 50's with a 22 inch High five on it. For your load, 21 inch sounds a bit steep.

Stainless is quite a bit more efficient than aluminum. It isn't even worth the effort to use an aluminum prop on that engine except for emergency repair.

I like the high five because it has a hole shot to die for. It's ventilated, so it lets the engine spool up quickly, then bites like a grappling hook and takes off. It stays in in the turns, and is smooth as silk. You sacrifice a bit (like 3 percent) of top end for it, but that's obviously not a big concern on the barge.

<<<CAVEAT>>> The stock lower on that engine is 4 1/4 inch hub, 1.78:1 gears. A 4 3/4 inch hub, 1.87:1, will bolt right up. You nead to determine which you have to get props and other parts for it.>>>

You have 1.78:1 gears in that engine. an 18" prop, at 12 percent slip, and turning 5500 rpms, would run 46 mph. That engine is in danger at WOT under 5500. 6500 won't hurt it a bit. I think it has a timing limit that backs it off at about 6000 anyway. I took mine off and let it spin a bit. (I had to add back a timing advance circuit to do it.)

If you want to have some family fun without spending a lot of money, you have a pretty good rig. It should do in the 40's with that engine. You won't win any races, but that's a pretty comfortable planing speed. 30 is about right for skiing. If it's propped right, and you run the trim right, it should pop right up on plane when you go.

One last thought. As the hp is a bit marginal for that boat, engine height setting, and maybe even angle are pretty critical. Even with a jack plate, it's a bit of trouble to mess with it, but that's where you'll peak adjust your performance.

hope it helps
John

 

[achilles555]

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

That engine is in danger at WOT under 5500. 6500 won't hurt it a bit. I think it has a timing limit that backs it off at about 6000 anyway. I took mine off and let it spin a bit. (I had to add back a timing advance circuit to do it.)

thanks so much for the detailed message. Could you please explain what you mean in the above quote - specifically WOT. I'm pretty much a rookie with outboards, so that whole paragraph is greek to me.

THANKS!

 

[j_martin]

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

thanks so much for the detailed message. Could you please explain what you mean in the above quote - specifically WOT. I'm pretty much a rookie with outboards, so that whole paragraph is greek to me.

THANKS!

Sure. WOT means Wide Open Throttle. Your engine should be mounted and propped so that it runs between 5500 and 5800 rpm when the boat is medium loaded and going flat out. (accordin to the book) If it is held to a slower rpm, it is lugging, and that's about the quickest way to wear out an engine. The XR4, in fact, is perfectly happy running 6500 WOT, much happier than 4500 WOT.

There is a combination timing module on that engine, bolted to the top and wired to the switchboxes, that is supposed to advance the timing a little if the idle speed falls below a threshhold, and also advances the timing at 5000 rpm from 19 degrees to about 23 degrees. At 6000, it's supposed to retard it to 17 degrees. If it's there and working, fine. If it gives trouble, remove it, set your idle timing by the book, and finish by ear, and set your max timing to 23 or 24 degrees. It'll run just fine. Mercury doesn't even sell the modules anymore because nobody will buy them. Doesn't hurt to run without it. Helps to advance the timing to compensate.

I do some flat out running, and some pulling (skiers), so I put in a switch and a circuit to advance the timing when I need it, and let the engine run a little cooler when I don't, manually. I'll do some more experimenting with that this summer. When I'm light, the water has the right ripple to it, and I stretch it out, she really flies, turning over 6500 with a 24 inch prop. Not much in the lake but a few inches of pad and the propeller.

It would be fun to know who you are and where you are. Yer profile is pretty bare.

hope it helps
John

 

[achilles555]

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

hi j_martin. thanks for the reply. I live in Kansas City, MO, and do a lot of fishing in Smithville Lake. I grew up around a lake (Lake of the Ozarks), and am really excited to get this boat ready to fish. It just seems like there's so much to do.

I'm going to shoot some pics tonight of my progress so far, just so everyone can see the progress on my boat.

Let me know what you think once I get the pics posted.

 

[bob stark]

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

just wondering if this motor circulates water at idle or just when in gear? I have the same motor and am looking for some advise

 

[j_martin]

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

Re: Just bought Merc 150 Black Max XR4 - Need Some Advice!

just wondering if this motor circulates water at idle or just when in gear? I have the same motor and am looking for some advise

The driveshaft turns all the time. The shifter is on the prop shaft.

It's possible that it wouldn't pee at idle if the water is cold. The only water that goes out the telltale is water that's been through the thermostats. There are other exits for the water, so if it isn't getting warm enough to open the t-stats, it won't pee.

If you are in normal water, it should pee at idle. If the poppit valve is stuck open, it won't. Running cold isn't good for the motor.

hope it helps
John

 

[achilles555]

Re: Just bought Merc 150 Black Max XR4 (Update)

Re: Just bought Merc 150 Black Max XR4 (Update)

Thanks to everyone who have helped me get this motor up and running to date - especially j_martin. I probably wouldn't have done it right without the help. Just wanted to give a quick update on progress over the weekend.

Friday: Took the day off of work to "play" with my new toy. I tested the switch boxes as explained in the previous posts. When I unhooked the wire between the 2 boxes, I still only had spark on one side. Replaced the bad switch box, and to my amazement, all six plugs had spark. YES! I then decided to rebuild the fuel pump. It wasn't as difficult as I had imagined. I expected to find a gummed-up and filthy mess when I got in there. To my amazement, it was nice and clean. The old round valves were hard as a rock, and one of them (there are 2) was damaged...bent over and warped...looked like it had been sucked through one of the holes and stayed that way. Very glad I took the time to rebuild the pump after I found the bad valve. The only problemI had was breaking off that D%$@ plastic rod that goes through the valve centers. They just wouldn't break. I ended up having to snip it off with pliers, and then use a small drill through the centers to clear a hole. Ended up working just fine.

Saturday: After dreaming all night Friday night about Mercury Outboards, I awoke Saturday morning excited to start again. I was going to attempt to replace the Water Pump. I removed the Prop, and then pulled the Lower Unit away from the outboard. Note to Self: Lower Units are much heavier than they look. I then turned a sawhorse on its side and sat the lower unit on it and began disassembly. All in all, the water pump was a piece of cake. The only problem I had was getting the lower unit to cinch back up to the motor. Not ever having done this before...well, let me just say that had someone been watching outside my garage...it would have looked like I was trying to do the Texas Two-Step with an outboard motor...for about an hour and a half. I finally got the lower unit in neutral, and the boat in neutral, and all 3 important parts lined-up (drive shaft, gear shaft, and water line), and it was complete.

With the water pump replaced, I then moved to the oil lines. Since they were already old, cracked, and 90% gone, I wasn't sure what went where. With the help of a few guys here on the forum, I figured it out and replaced the lines. Only 2 to replace. I then bled the lines, and called it a day. Piece of cake. Getting closer...

Sunday: I wanted to hear her run. This tune-up wasn't taking nearly as long as I had thought. I needed new gas and oil. The fluids that were in there were 7 years old. I tried pumping the old gas out with the bulb. Nothing was coming out. I got lucky with the gas. The tank was dry. It's an all aluminum tank, so I can't see in it. I decided it should be OK. There are 2 oil tanks to deal with. A "reserve" tank for the oil injection that sits on the front of the outboard, and a 3 gallon remote tank that sits in the boat. Both were full of old oil. I drained them both, and realized that there was nasty old sludge in both. I spent about an hour swishing gas around in them trying to break-up the sludge, and finally got that out. I then filled the reserve tank with premium Mercury 2-cycle oil, and the remote tank about half full.

I then mixed a six gallon tank full of fresh gas 50:1 (just in case my oil injection wasn't working) with oil, and poured it in the gas tank. Next were the carbs. I opened the plastic cover to the carbs, and they were clean as a whistle. I was once again amazed. I cleaned the sludge that had collected around them and at the bottom, squirted a little starting fluid in each (for good measure) and screwed the cover back on. Now I'm getting REALLY close.

Next, I reattached the fuel line, attached the flush kit, ran the garden hose over, and went to get my son for the moment of truth: I lifted the throttle, pushed the key in for a little choke, and turned her over. The engine cranked, cranked, cranked, and then...it fired and stalled. A good sign. I then turned the key again - without choke or throttle - and then BAM. She fired-up and it was beautiful. I let her run long enough to see a little water come out of the pee hole, and then shut her down. This was going was more smoothly than I expected.

My son and I loaded up in the truck and headed to the closest lake ramp. I backed her in and fired her up again. First turn of the key and it fired right up. She purrs like a kitten. Water squirts out of the pee hole. It shifts into gear like it should. So far, so good. I can't take her out for a swim yet, cuz I'm getting ready to replace the steering, but I can't help but think that all is going to be well. Remember, this boat has been sitting, uncovered, for over 7 years. It was run and then parked, seven years ago. I think this whole experience says a lot about Mercury Outboards. To those of you out there that are looking to buy a new motor - all I have to say is "If it ain't black, take it back!"

Thanks again to all who have helped. I'll let you know once I get her in the water and get to give her some throttle. AC.

 

[j_martin]

Re: Merc 150 Black Max XR4 - Need Some Advice! (Update)

That '88 XR4 is a steel sleeved 2.4, one of the toughest motors murkery ever built. Not only that, but it's actually the old 175, prop rated for 150. It's a little over 160 ponies right out of the box. It's a really strong motor for a stocker. Yer gonna like it.

Be sure your steering is good. Dual rack is considered the minimum for this engine if it'll go over 50. (You could get away with rotary on a pontoon, for instance)

John

 

[achilles555]

Re: Merc 150 Black Max XR4 - Need Some Advice! (Update)

hey john. the boat came with a dual cable detmar rack and pinion system. the steering was locked-up tight. i had a heck of a time trying to find replacement cables, but finally found a replacement set on ebay. $175 shipped to my door for both. only thing that might be a problem is that i had to buy cables that were 1.5 foot longer than the originals. the originals were 13', and the only thing i could find was 14.5'. i'm hoping i can hide the slack in the walls of the boat. haven't installed them yet...so i'm a little nervous. the new cables are smooth as silk. thanks for the heads-up.

 

[j_martin]

Re: Merc 150 Black Max XR4 - Need Some Advice! (Update)

My engine is on a 6 inch jack plate. The rear cable was bent too sharply, and failed at the bend. When I put in new steering, I put a second hole in the motor well, aft the first one, to pass that cable through so it would not have such a sharp bend in it.

John