Mercury XR2 150 stuggling to get on plane.

[llyons]

You said in your Original Post "once its on plane it gets going like it used too at WOT"
Then later you say your top Rpm is 4500.
So has 4500 Rpm always been the fastest the engine has ran?

Hi, No sorry for the confusion. I just briefly looked at the RPM gauge when I was on plane and saw the 4500 and did not watch the entire time. It could have been Higher and definitely has been up in the 5800 range in the past. I am going to take it out today to see if I can watch this more closely.

 

[QBhoy]

Hi Recently in the last 3-4 times out on the boat, the Merc 150xr2 doesnt have the hole shot it used to. It does get on plane but takes about 300 yards and once its on plane it gets going like it used too at WOT. There is no miss. The fuel lines from motor to fuel tank were all changed and the fuel tanks drained and new fuel added. The priming bulb does not seem to get hard but on plane at WOT, it does not have any sputter from a fuel shortage.

I checked the timing for throttle pickup and it was 11deg ATDC and at WOT it was 23 BTDC. This seems to be correct. i also adjusted the carburetor linkages to set the roller against the throttle cam.

i did not rebuild the carbs but did a year ago. I did clean the 6 main jets on the bowls.

What could be causing the motor to not have the hole shot it used too but still achieve the same top end after getting on plane?

Just thinking about this there.
Tell us a little more about the situation around it not getting going for a while (or as quick as it used to) ? Do you mean that it feels as if it’s bogging and getting choked or strangled as you accelerate? Or does the engine seem to freely build rpm but the boat doesn’t seem to make the progress or have the pick up it used to ? If it’s the latter, I’d ask more about the notion around the prop being a possible cause. Maybe in particular around any prop changes causing this ? Or perhaps the prop is of the type to have a pvs vent plug system that allows slip through venting exhaust over the blades for a while until it seals at quicker speeds. Or perhaps even a prop hub spun situation?
Failing that and back to option one…I’d first off, run it off another separate and remote fuel tank. After checking the health of the fuel line, primer bulb and fittings each end. Try the bulb pumping squeeze with the line disconnected from the engine end. Make sure it holds pressure and doesn’t leak. Listen for any induction of air on the suction side and any leakage of fuel on the pressure side.
All being well there…is run the engine with the hood off and carb intakes exposed. Then manually choke each carb with cardboard over each or close to each intake (whilst at various throttle positions), taking note of any noticeable change in running behaviour that might indicate one of the carbs showing a different state to the other two, if you get me.
Think I said before, but definitely get a meter across that main fuse carrier holder too. Make sure it’s showing full continuity. That’s what caused issue on mine. Get a meter across the battery too whilst going through various rpms and make sure there is nothing odd there. Check continuity of the cables too. Did you say you tested the AC output and on diode setting on the meter of course ? Maybe you did, thinking back. Of course we have ruled out spark plugs and HT leads and their health too by now ?
Keen to see you resolve this and also to learn what you find, should the answer be outside the norm. I have one of these on a 16ft cvx16. Have her running superbly for the most part..but just recently she developed a wee dead spot at full throttle. For a few seconds she holds back, then roars up the last few hundred rpms to where she should be. Need to look into that yet.

 

[racerone]

Take it to a shop with a dynamometer.-----Test power output of the motor.-----That will separate whether it is an issue with the boat or the motor.----That would be a few beer tokens well spent.

 

[llyons]

Sorry for my long post.

QBHoy, thanks, I am hoping I can find what the issue is with the limited time I have to look at it. Fishing in the gulf coastal water is great this time of year. I was going to mention a few more things.

a little history the last couple months

1st, a couple months ago, my son and I went out fishing in the coastal areas and the first time trying to get it on a plane, it had this same sluggish scenario. not missing but not enough power to get it on plane. Later we got it on plane and it responded normal like this the rest of the afternoon. No issues. Almost like the first plane helped burn some fouling off of the plugs. So first time sluggish, the next half dozen moves it performed as it should.

then 2 weeks later we took it to toledo bend on the family camping trip and the first time and second time it jumped up on plane with no issues. After that it went into the sluggish scenario were it wouldn't plane. Keep in mind that Toledo bend does have a bunch of stumps and im sure the prop hit a few when we where idling over in a stumpy areas. Could this cause the prop to spin off the hub? would it even plane after this? I did not notice the motors rpms ramping up like it was cavitating and I would think you would hear this if the prop was slipping.

At home I decided to replace the fuel filter, priming bulb and engine fuel connector and line back to the tanks.

2 weeks ago we went out of pointe a la hache to our favorite red fishing spots and it was sluggish and would not plane, since the put in was 2 hours from home, we decided to fast idle out to one of the spots about 2 miles out. Once we got out there it seemed to slowly build up RPMs and eventually got on plane and we went ahead and went out to the better spot about 5 miles away. (i know that was risky but we killed it with line ripping 10-20 pound reds and 2-4 pound sheephead all day long (well for the 4 hours we were there.)

On the way back it did not get on plane so we fast idled back to the dock. However near the end of this trip home, i heard some times where it seemed like the gas started coming in or the RPMs started picking up like it was cutting in so we where able to get it on plane for the last half mile.

after checking timing and disconnecting the idle stabilizer I took it out to the closest area and it was able to get on plane but took almost a 300-400 yards to be on plane and we did this 6 times with the same result.

again to rollup everything I have done and noticed.

- i have the mercury outboard service manual from when I bought the boat.
- we checked the timing and throttle pickup was 11 atdc and WOT was 23
- all the carb linkages were fine tuned
- pulled out all the primary jets on the bowls and cleaned them but they seemed ok
- the cylinders are all firing as evidenced by timing light on each line
- We measured all the impedances of the stator and they were all in spec
- we measure all the impedances of the trigger and that was also in spec
- measured the DVA of the two blue lines on the power packs an it was 180 and moved up as I throttled the engine up.
- i verified the trigger advances or moves without any catch or delay

- the priming bulb does not get hard even if I have the gas line into a separate gas can.
- the first time I put on the bulb and primed it I remember it getting hard
- made sure priming bulb is pointing toward motor and tried pointing it up as this was recommended. No change
- I detached fuel line at the oil induction check value and even made sure it was primed by holding my finger lightly on the end and priming letting gas shoot out under my finger.
- seems like some bulbs dont get hard or I have another issue.

if there was fuel in the bulb with no place to go it would be very hard but i dont have that?

Do most shops have a dynameter they will test your engine with? is this normally done with prop off? I dont like to give up many of my beer tokens... i keep those pretty close

I guess my next steps are the rebuild the carbs and fuel pump or put it in the shop and let somebody smarter than I figure this out.

 

[redneck joe]

Check the fuel filter gasket to ensure not sucking air.

 

[llyons]

Check the fuel filter gasket to ensure not sucking air.

Hi Joe, I am not sure what you are referring too. I have an inline fuel filter after the fuel pump? Do you mean the fuel pump gasket?

 

[QBhoy]

Hi Joe, I am not sure what you are referring too. I have an inline fuel filter after the fuel pump? Do you mean the fuel pump gasket?


View attachment 392772

Hi. I’d check the fitment of that fuel filter maybe. That looks like the type of in-line filter from newer models with the quick connect fittings. I’m almost sure the older type that’s suitable for your engine is of a slightly different design where the fuel lines attach each side. Your lines are barely holding onto things each side there. The pipe hose normally reaches much further onto the filter male fitting spigots each end.
Anyway…despite the carb clean previously…hate to say it…but I’d be really thinking about taking them off again for a proper clean. Even an ultra sonic clean to make sure. Pain in the backside, I realise…but I’ve learned my lesson on this far too many times. Sometimes you just need to start again and make sure they are properly cleaned. Then you can absolutely rule them out.

 

[dingbat]

Hi Joe, I am not sure what you are referring too. I have an inline fuel filter after the fuel pump?

The parts diagram doesn’t show a in -line fuel filter on that motor. Fuel filters typically go on the vacuum side of a pump anyhow

Have you checked/changed the screen/filter inside the fuel pump?

 

[QBhoy]

The parts diagram doesn’t show a in -line fuel filter on that motor. Fuel filters typically go on the vacuum side of a pump anyhow

Have you checked/changed the screen/filter inside the fuel pump?

I was thinking along these lines too. I’ve seen them on slightly later models, or perhaps as an owners diy addition. But if she’s anything like the age of my 150 from the 80’s…I don’t have one like that there for sure. Despite that or either way, that particular filter is certainly not original and intended for the much later models. Even looks like it might be the same part that my 2016 merc 4 stroke has. She has quick connect fittings with red tabs either side.

 

[redneck joe]

Absolutely not an expert here, just thinking if sucking air somewhere. My 82 50 hp was along with a couple other issues.

 

[Chris1956]

Did you ever check the fuel pump diagram for leaks? If it leaks, it can load up a cylinder or two at idle. They often clear up, after you struggle to get on plane.

 

[llyons]

Hi, Wanted to give an update. I finally took the boat to a local outboard shop that was highly recommended. Casey Marine in Gonzales. It turned out being just 2 spark plugs that had gone bad. I was surprised and bummed out at the same time. Surprised that it was something simple and didnt cost much to diagnose and fix ($130) and bummed out that I had checked the wires for firing but never checked the actual plugs. Plugs on cylinder 2 and 5 had stopped working. I have more hole shot than I can every remember before. It literally jumps out of the water.

any way I am glad that it did not cost much and that I was not over charged.

Thanks everyone for the help, advice and suggestions.

 

[redneck joe]

Old and burnt up or just up and died?

 

[Faztbullet]

2 & 5 are the same coil in timer base, trigger could be failing and firing the switchbox late thus causing them to foul out. It also could be a bad advance box as it effects the trigger bias to switchboxes

 

[llyons]

2 & 5 are the same coil in timer base, trigger could be failing and firing the switchbox late thus causing them to foul out. It also could be a bad advance box as it effects the trigger bias to switchboxes

Interesting, So i need to pay closer attention to this. When you say advance box, you mean the idle stabilizer module? I just recently (after this started happening) disconnected this.

 

[quicktach]

Hi Recently in the last 3-4 times out on the boat, the Merc 150xr2 doesnt have the hole shot it used to. It does get on plane but takes about 300 yards and once its on plane it gets going like it used too at WOT. There is no miss. The fuel lines from motor to fuel tank were all changed and the fuel tanks drained and new fuel added. The priming bulb does not seem to get hard but on plane at WOT, it does not have any sputter from a fuel shortage.

I checked the timing for throttle pickup and it was 11deg ATDC and at WOT it was 23 BTDC. This seems to be correct. i also adjusted the carburetor linkages to set the roller against the throttle cam.

i did not rebuild the carbs but did a year ago. I did clean the 6 main jets on the bowls.

What could be causing the motor to not have the hole shot it used too but still achieve the same top end after getting on plane?

Check all wiring and especially grounds. Check plug wires and plug fits to spark plugs. Check stator output. Check rectifier and diodes. Battery and connections all ok?

 

[QBhoy]

Hi, Wanted to give an update. I finally took the boat to a local outboard shop that was highly recommended. Casey Marine in Gonzales. It turned out being just 2 spark plugs that had gone bad. I was surprised and bummed out at the same time. Surprised that it was something simple and didnt cost much to diagnose and fix ($130) and bummed out that I had checked the wires for firing but never checked the actual plugs. Plugs on cylinder 2 and 5 had stopped working. I have more hole shot than I can every remember before. It literally jumps out of the water.

any way I am glad that it did not cost much and that I was not over charged.

Thanks everyone for the help, advice and suggestions.

Did you get a look at the plugs that were bad ? That can tell you a story or two.

 

[llyons]

Hi, was out in the boat yesterday after recently getting some work done and spark plugs replaced. Before spark plugs 2 and 5 had gone bad per the shop. After replacing the boat was flying out of the hole and ran well. However on the way in at WOT, the motor died. After looking at the compression on each cylinder, it looks like cylinders 3 and 4 have 0 compression. 1,2,5 and 6 have 123-125 compression.

i know this basically means this motor is shot.

I have a couple questions.

What would suddenly cause both 3 and 4 to go out? both are middle cylinders. I can definitely see the pistons are moving in 3 and 4. Picture of 3 spark plug is below?

Also, this is an older 87 champion that I recently had re carpeted, reupholstered, new trailer, etc. I have 7k in the update

Am I better off getting the motor overhauled? Any thoughts on what that cost?

Is there cheaper or better alternatives then getting this motor overhauled? Perhaps a second hand motor from a motor exchange?

Looking for any advice and suggestions. Thanks in advance.

 

[Faztbullet]

Preignition problem....triggger,advance box or switchbox

 

[QBhoy]

Oh jeez. Sorry to hear/read this. Nothing worse.
That plug and it’s condition, doesn’t look or tell a nice story, I’d think.
Just before we all assume or conclude the worst…any pics or idea what she looks like, looking down into 3 and 4 ?
On just the odd and lucky occasion, an optimistic thinking fella, might just be of the mind that reports of an absolute 0 compression reading across two cylinders, can sometimes be caused by the failure of a common (to both) interface seal. More likely between two neighbouring cylinders though, rather than opposing, if that’s what you’re reporting. Common only to the latter (and the rest) would likely be usually the exhaust chamber between both banks.
Ruling out all and any optimistic thinking or notions, would be the report of obvious piston and or cylinder damage, of course. Debris on the plugs, as pictured, may be indicating such a thing, unfortunately.

Maybe silly to ask this now…but did you mention or say previously, if she was still running with her original oil injection, or was she pre mix converted? Again silly to mention, but even if she was safeguarded, with the latter option, most owners of these particular engines, might argue that a fairly potent oil mix is called for. More than the usual 50-1, at least.