1986 xr2 150 falls boggs after 4200 rpms.

[17rogue70]

this is what i know . engine sat for 2+ yrs. installed on 1989 silverking 19' after some refurbishing. replaced water pump kit, thermostats, poppet and carbs were rebuilt. temp is good , oil injection is working as should. run up through the rpms , all seems good til about 4000 4200 then starts to fall off. kind of boggs down , sometimes when you cross your own wakes it tries to pick up in rpms to about 4600 .this has me a little puzzled. compression is 130 psi across all cylinders. didnt do a leak down test though. one more thing the fuel pump was also rebuilt along with a brand new complete fuel system. tank, lines, filters and screens.



thanks for readind and any responses givin
mike

 

[SparkieBoat]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

most likely a fuel related issue...either carb/s or fuel pump or line/connection sucking air or bad tank pickup or vent. pretty much gonna be one of those, assuming you got good spark on all cylinders, did a proper link and sync and timing is correct. o yea..remove the idle module thingy, and adjust timing to 25 BTDC at WOT..search forums for procedure.

 

[CharlieB]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

Has the motor always been on THIS boat?

It is possible that the motor may have been propped for a lighter boat and crossing the wake unwetted the boat enough to allow the motor to gain RPM until the craft re-settled in the water.

Does pumping the primer bulb make any difference in WOT RPM?

Double check your tune-up adjustments as Sparkie posted and repost the answers to what I've asked.

 

[17rogue70]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

charlie, no this engine was on another boat. it came from an 86 ranger bass boat then installed on a 1989 silverking flats boat. the ranger weight is unknown to me. the silverking weight is 1150 +/- according info i have found. as stated the WHOLE fuel system has been replaced, carbs rebuilt, linc and sync done . the prop is pitched at 23.havent tried pumping the bulb to see if it made a diff or not.
i know nothing about adjusting timing on outboard engines, give me chevrolet or ford and im good , but an outboard and im lost. have good spark across all cylinders, 7/16 jump as should be per my reading.

thanks to you both for all info and diagnosis as well as your time
mike in orlando

 

[17rogue70]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

the ranger bass boat is 2' shorter but 50 pounds heavier than the signautre , silver king grande master 19' flats boat . s.k has no wood , where the ranger does. does anyone have an idea what the 23 p prop should turn at? engine is a 1986 merc xr2 150 carbed engine.

 

[aussieflash]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

Im thinking 23p is a little high.Im running 19p on 17' boat and im using similar motor as you.My boat may be a little heavier than your 19' Silver King.Correct prop should allow you to reach correct WOT,and the XR2 should spin at around 5500-6000rpm.

 

[CharlieB]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

Max timing can be check cranking, plugs removed, all plug wires grounded, throttle wide control lever wide open, remote starter button and timing light.

Watch out for the spinning prop or take it off.

If your motor has an idle stabilizer module, remove it and toss it into the trash, set max timing to 23 BTDC

 

[17rogue70]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

you metion spinning prop , do you mean in gear and w/o throttle or in neutral w/o throttle? idle stabilizer module, where would that be? does this engine have a timing pointer/ indicator? is there a link to these parts you mention? unfortunately , i dont have a manual for this engine. thank you for the responses and patience. i apologize for so many questions

 

[aussieflash]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

Have you ever had this boat at WOT 5500-6000 with that prop??If not have your boat weighed(with fuel,supplies and avg passenger total weight)in some cases you could be carrying around 600-700 pounds of extra weight.Take that info to a dealer who fits outboards for help.
Get a manual before messing with timing.

 

[Faztbullet]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

Where the carbs rebuilt or just cleaned and new gaskets? It really sounds like a float level is off or shellac is floating around in a high speed jet. Also a 25p is way too much prop for that set up more around a 21p...

 

[17rogue70]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

aussie, no i havent had this this motor to w/o throttle. the engine is new to me. faztbullet, carbs were rebuilt. like stated earlier, NEW FUEL SYSTEM front to back. tank lines,screens and filters.fuel pump was rebuilt. new water pump kit, thermos, poppet.linc and sync was done also. good spark on all plugs and 130# on all cylinders for compression. it could be over propped as said previously . iwas thinking maybe the high side of the stator? or are the rpms to high in range?

 

[17rogue70]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

gonna try the prop first. and go from there . try a 14x17 and see if that is the problem. from a 23p to a 17/19p to see what happens. what do ya guys think? thaat wake thing got me to thinking . maybe it is over proped big time. we ll see

 

[aussieflash]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

Should def get more out of 19p.Let us know what happens.

 

[17rogue70]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

sparkie was correct, was still trash in the bottom starboard carb jets. cleaned and now its getting 5600 rpms @46 mph. not as fast as thought but fast enough for me. prop size is 14"x23" . one last question , if i were drop to a 21"or a19" pitch prop , would my top speed increase and my holeshot be quicker? but what would it do to my rpm range? rule of thumb is 200/400 more rpm per inch correct?

thank you so much for ALL SUGGESTIONS AND ANSWERS to help with this build and troubleshooting

 

[SparkieBoat]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

that engine likes the high 5K -low 6K RPM range, a 21P or 19P prop would probably do you real good, I would get one that has a large cup, you would prob increase hole shot and keep about the same top end, you may lose 1 or 2 MPH. you may even gain 1 or 2 MPH. every boat and prop are different. I would increase my oil mix to about 40:1 if you choose to run over 6K very much. I would also recommend premixing and capping off your oil pump if you still use it. I just did one on my uncles motor today, he has exact same motor. we also removed the idle module and set timing to 23 and 4. that is a real bullet proof motor once you do this and take care of it..make sure it never over heats,, test overheat alarm a few times a year specially if its old. I have one just like it too..I think mine is an 1988 model. saving it for the right boat. here is a good prop..but I would recommend either contacting a manufacturer directly or a local shop who will work with you on a test basis till you find the right prop. nothing like being able to test run a few different props till you find the exact right one. http://boatpropellers.iboats.com/Me...S5862X_Propeller/309/19314/?*******=187710568

 

[17rogue70]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

what is involved in bypassing the oil injection pump? i know i would be removing the bulk tank in the hull and the tank on the engine ,but how do bypass the pump. what needs to be plugged off and any wiring that needs to be deleted to the alarm system?

again thanks for all info and answers . it has been a major help to a do it yourself type person as myself , and you have saved me a ton in mechanicsfees. if you are ever in central florida look me up , the least i could do is buy you a frosty beverage of your choice . or maybe a day chasing a redfish along our eastcoast.

 

[SparkieBoat]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

I love redfishing, we have them up here in Savannah mostly during the fall. all you need to do is reroute your fuel line from the oil pump connection directly to where fuel comes into the cowl, I had to twist the fuel fitting with a 9/16 wrench so it did not kink the fuel line, I also had to cut about 2 inchs off the fuel line so it would not interfere with the linkage, ( I had to reroute the fuel line in front of the linkage and kinda tuck it in between the 2 bottom carbs.) this will by pass your oil pump. just behind your oil pump there is a rectangle box that has some wires going into it, (from your oil tank sensor) this box has a large blue wire going to the block as a ground, remove the screw and disconnect this ground, then tape it up so it will not ground, I used a zip tie to hold it to the wire harness, be sure to reconnect the other wires grounded there. BE SURE TO PREMIX YOUR FUEL AND PUMP THE PREMIXED FUEL THROUGH YOUR FUEL LINE BEFORE RESTARTING YOUR MOTOR. (your fuel line will be filled with unmixed fuel unless you do this) Also test your over heat alarm, on the right side or your motor (from behind) there is a wire going from the top/center of your head (your overheat sensor) to a post with a couple other wires, turn on your key then ground that post (I used a screw driver across the block then touch the post) it should buzz.

 

[17rogue70]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

thanks again sparkie, i will be performing this tomm. as today i was busy building a kickin oyster steamer for buddys girlfriend that shucks for small parties . thanks again you have helped so much.

 

[SparkieBoat]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

cool...post a pic of the steamer...you making it out of SS or alum? just had an oyster roast sat night..umm good. If you need some pics of the conversion let me know.

 

[17rogue70]

Re: 1986 xr2 150 falls boggs after 4200 rpms.

ill get some pics of the steamer as soon as i get around it again. if you could send some pics ,that would be great. havent been able to get to it yet any ways.