Problems with my 300XS

[Capt Ryan Rachunek]

I have a Merc 300xs with about 35-40hrs on it and it won't get out of the hole. I run a SCB and others with this same setup have no problem getting out with a 28 or 30 pitch Bravo I. I have tried everything that I can think of and I cannot diagnose the problem. I tried running a 24 pitch Bravo I and I still can't get the holeshot out of my 300XS that I can get out of the same boat rigged with a 255 Sport XS. I am also running about 8-10mph slower on top end as compared to identical boat running the exact same setup with no more that 10-20lbs difference in load. The issue continues to get progressively worse. I have had Merc techs run it on a computer, but they say everything is within specs. I am lost for ideas, maybe someone on here knows of something I have not thought of. I want to run it on a dyno, but no one that I have found has one that they will run a 300XS on.....:mad:

[WILDMAN]

I had one that had a bad coil pak. It did'nt show up on the puter either. I changed them under warrantee and it's run great since.

[Capt Ryan Rachunek]

Any idea on what the output should be on a good one? Best method to test?

[WILDMAN]

There really is no way to check it. Sometimes one will seem bad, but it's another one. I took all six off another motor and it worked fine. Then my dealer got me six new ones.

[Capt Ryan Rachunek]

I'll try that, thanks for the info.....

[Dutch]

if you can find a dealer with a test tank. they can keep the tester hooked up and try to run the snot out of it.

[Capt Ryan Rachunek]

if you can find a dealer with a test tank. they can keep the tester hooked up and try to run the snot out of it.

Thanks, but it has already had the snot run out of it with the tester on it......and it wasn't in a tank :thumbsup:

[WILDMAN]

I've talked to several good Merc guys. They all say the coils or ECM's, or whatever they are called have no tests. Just swap them with another motor and see what happens. The motor I had the problem with did the exact same thing as yours.

[Capt Ryan Rachunek]

I've talked to several good Merc guys. They all say the coils or ECM's, or whatever they are called have no tests. Just swap them with another motor and see what happens. The motor I had the problem with did the exact same thing as yours.
I appreciate it.....I've got a really good Merc guy in Port A, but I haven't been able to get it down there for him look at it yet. I'll let him know what you said when I drop it off Monday.

[WILDMAN]

If he has any questions, call me and I'll give you my guys number. My work no. is 386-761-8050

[Wayne Cammidge]

Put the boat on the water with the computer and while running at WOT do a cylinder mis-fire test. Only way to find a bad coil. Swap it out and retest to make sure it is the coil and not an injector or other problem. Could also have a bad spark plug.
Cheers Wayne

[merctech5591]

as randy said there is a bulletin on the coils. a simple spark output test will verify a bad coil.. also fuel air pressure are critical on the hp motor's . a loss of air will drastically reduce power to the motor and will not be seen by the computer..

[Fast Fig]

as randy said there is a bulletin on the coils. a simple spark output test will verify a bad coil.. also fuel air pressure are critical on the hp motor's . a loss of air will drastically reduce power to the motor and will not be seen by the computer..

Just noticed the the location on your post......................When did you finally moved to Texas?
Hope everything worked out well for ya.
How different is Texas from So.Fl.?
Peace!FIG

[Capt Ryan Rachunek]

Thanks for the info guys.....I'll post what the outcome is ASAP.....

[merctech5591]

Just noticed the the location on your post......................When did you finally moved to Texas?
Hope everything worked out well for ya.
How different is Texas from So.Fl.?
Peace!FIG

texas is good, deff different from so florida.. i really miss the water's and location's to run to. but everyting here is fresh water.. engine are alot easier to work on cause there aint no salt.. later rick

[Largemouthlou]

Just a shot in the dark but if ya have the 1.62 gears then the props need vent holes to get her turning.. Have ya tried an overhub prop to see if the holeshot changes??

[WILDMAN]

Just a shot in the dark but if ya have the 1.62 gears then the props need vent holes to get her turning.. Have ya tried an overhub prop to see if the holeshot changes??

I also thought about that, but he's losing it on the top end too.

[Capt Ryan Rachunek]

Dropped her off with Merctech5591 today, thanks for the help guys.....

[Capt Ryan Rachunek]

Talked to Merctech5991 and he said the gaps on the plugs were all over the place and one plug had an electrode that was twisted. No one that I know of has been in the motor since it was shipped from the factory. Weird.....Hopefully I'll be picking her up tomorrow.....

[merctech5591]

took the boat out today for a ride.. lake was really nasty so only got 71 mph.. @5200 with a 27 trophy there's plenty more to get but had no water to run in.. . i'll be taking it to the river tomm and ive got 5 prop's to try.. i'll keep you posted..

[merctech5591]

well took the boat out this morning was at the lake by 7:00, it was awesome no boat's and plenty of clean water.. i tried a 30p lab bravo, 27 std bravo, 27 trophy, 25 tempest, and a 5 blade hill 26p. all prop's ran in the 70's.. best prop's for the boat was the 25p tempest, better hole shot and much more acceleration. and the 26p hill..both of these prop's ran 75-76mph. a 28 5 blade may yield a bit more speed as it would turn it up to 6200 rpm.

ryan call me up, the boat will be ready for p\u tomm.. thanks rick

[stokernick]

so what was the problem?poor spark plug gaps??

[Capt Ryan Rachunek]

Rick, PM me your phone number, my Blackberry died and I lost all of my numbers....

[merctech5591]

so what was the problem?poor spark plug gaps??

spark plug gap's were from .024 to .030. spec is .032. also one electrode was bent and one would not fire under load.. so two bad plugs was the problem. i haven't had many problem's with the 300xs and i have rigged and sold a ton..

[Markus]

i haven't had many problem's with the 300xs and i have rigged and sold a ton..

Well, given the weight of today's DFI and 4-stroke engines, a ton of engines is not as many as it used to be... :eek:

[merctech5591]

well, Given The Weight Of Today's Dfi And 4-stroke Engines, A Ton Of Engines Is Not As Many As It Used To Be... :eek:
I Should Refrase And Say A Few Ton.. :d:d

[diamond-back]

ugh. well now I can add to this post.

Our 300XS has 104 hours on it. A couple weekends ago, I was out with some friends when the motor started not being able to turn the RPMs like normal (only around 5000 to 5200) and after more cruising, it got worse, and worse. No horns or error messages on the Smartcraft gauges. So then, it gets so bad, that the boat cannot even plane out.

After pulling all the plugs, the #6 plug was fouled pitch matte black.

We replaced the plug, and took it back out. It seemed to be back to normal (thank god), but that only lasted about 5 minutes. I was able to get my 6200 RPMs out of it for a brief 10 seconds or so... but then it just keeps missing (i guess) and is only good for about 5000. And the hole shot is TERRIBLE. I tried to have my dad tow me for a barefoot pull. He was WOT trying to get me surfaced... and then, once I was on my butt on the surface of the water (being very very little drag at this point) the engine KICKED and rreally messed me up.

So anyway, we pulled the #6 plug and there is carbon on it, too. Anyway... off to the shop... I'll keep yall posted.

[merctech5591]

sounds like a bad fuel injector dumping too much fuel in that one cyl.. or a coil failing.. i guess i've been lucky with mine no problems yet.. :thumbsup:

[Capt Ryan Rachunek]

I just wanted to give a big THANK YOU to Merctech5991. Rick has bent over backwards to help me out in one of the busiest times of the year for boat mechanics. He was able to quickly fix my problem and has been a pleasure to do business with. Anyone in the Houston area who needs a good Merc mechanic should look him up at Capt. Kirk's Marine in Spring. Top notch guy and a top notch outfit. THANKS AGAIN RICK!

[Michael Dixon]

Got a close friend with three 300xs and has had a bunch of coils go out lately. May not be ur problem but there are some with bad coils out there. Just something to keep in mind

[diamond-back]

two things were wrong.

The tracker valve was torn, and then they found one bad wire in a harness that goes to all six coils... causing it to malfunction.

Can't wait to get it back in the water... it's been too long!!!!!!!!!!!!! :cool:

[Capt Ryan Rachunek]

I know the feeling.....I thought mine was just the plug problem, but it is still not running right.....:mad:

[TUNNEL T]

have a pair ,changed fuel filters regularly ,lost one lower at 60 hrs , changed plugs at 100 hrs ,then lost diaphragm in fuel rail on port motor.thank godfor warrantee cuz that would have been 1200$ . but all in all these things run awesome 184hrs and still singing 6200 with a set of 35 cleavers !!!!!TUNNEL T

[diamond-back]

ours was outta the shop for like two weeks... then, the compressor froze. Lost a needle bearing...... good thing we were just goin slow takin it easy (40mph)... and like TUNNEL T said - thank god for warranty that compressor was over 1,000$ !!!

But 124 hrs and runnin strong too :) i love this motor. just a freak issue.

[War Canoe]

Issues have been
1. Cracked head...caused rough running while in gear at slow speed.
2. bad computer brain...alarm stayed on
3. lightning et 4 blade labbed props....Had 3 blades come off in 60 hours...
4. Little oil tank mounted to block cracked.

All warranty stuff including 3 new props...went to 28 and 30 choppers.

I run a 19' Cougar...What hull are you running? My friend gets only 100 MPH out of his 20.4 Stoker w/ 300xs, while I get 107+ out of mine. He was spinning only 6K rpm, I get 6400....make sure your computer brain is a 6400 rpm brain, they tried to give me a 6K brain when I had it replaced !!!:mad:

[blkmtrfan]

Hey War Canoe how about some more pics of your boat, from what I can see your paint combo looks awesome :thumbsup:

[Markus]

Issues have been
1. Cracked head...caused rough running while in gear at slow speed.
2. bad computer brain...alarm stayed on
3. lightning et 4 blade labbed props....Had 3 blades come off in 60 hours...
4. Little oil tank mounted to block cracked.

All warranty stuff including 3 new props...went to 28 and 30 choppers.


Ouch. This is getting expensive for Mercury... :(

[War Canoe]

Ouch. This is getting expensive for Mercury... :(

My '06 22' Daytona 275 Verado has 502 hours ...

The 300xs is 1 year old with 120. If anybody is going to eat up parts, its me. First Protection Corp offers a 2+4 warranty....For 2900.00 you get 4 more years coverage on all oil lubrcated parts...I have been using outboards for 15 years, I have used 175K in warranty parts total..That spans 15 engines...Money I didn't have to dish out. I am ahead of the game :cheers:

[War Canoe]

Hey War Canoe how about some more pics of your boat, from what I can see your paint combo looks awesome :thumbsup:

I built this with my brother...Started a a four seat 1984 19' Cougar tunnel $1700 with trailer.

We went in line seating for balance...28 inch custom car floor shifter with Tiki Head, custom in line 27 gallon fuel tank with twin 9 gallon side tanks (stock tanks) for 45 gallon capacity. Built custon hatch cover to prevent swamping and cover the oil, battery, fuel, and trim pumps. Reinforced every interior stress point and added the 300xs for power. It has run 107 mph to date and can maintain 100 mph all day. Wide open 5 mpg from the 300xs...cruise at 75 mph and get 6+mpg...Here's a couple more pics of the build.

[War Canoe]

and a shot of the Northern California fires from the boat...:)

[blkmtrfan]

Cool boat :cool:

I like it :)

[1BadAction]

Tiki-man, Classic hotrodder stuff. Nice rig. :D

[R.grover]

mines got 110 hours on it mainly used for family skiing or ski racing.
light boat running merc et props from 26 to 32 pitch only had a set of plugs at 92 hours as could not get over 6050 rpm when it would pull limiter with 32 et boat only all day. u guys running bravo props any gd? what bout on light boat 4 ski racing?

thanks guys

[War Canoe]

mines got 110 hours on it mainly used for family skiing or ski racing.
light boat running merc et props from 26 to 32 pitch only had a set of plugs at 92 hours as could not get over 6050 rpm when it would pull limiter with 32 et boat only all day. u guys running bravo props any gd? what bout on light boat 4 ski racing?

thanks guys

300xs 19' cougar tunnel
27 bravo labbed 4 blade....great for turns and accel..93 mph
28 merc chopper 2 ....102 mph great hole shot
30 merc chopper (ordered)expect 105+
30 lightning et labbed 4 blade ...decent holeshot, great mid and top, great cornering...105 mph on the limiter 6400
28 Lightning et labbed 4 blade...great holeshot, great mid 102 mph on the limiter Best overall performance. Problem...props good for 30 hrs max.(blades break)
32 3 blade Hoss...best top end 107 mph...does not like smooth water...
34 merc 4 blade cleaver...hated it...102 mph ..squirrley on my hull.

[Wizard]

I got the third motor off the line in Aug. 06. I've had it for two and a half years and still only have 66 hours on it. :eek:

When I got it I had the same problem. It just did not seem that strong. When I went to check the plugs I found the number six plug cracked through the electrode. Ran and idled fine but just down on power. That's one tight fit for that plug. I'm sure some of them came from the factory with pharked up plugs in the #6 hole.

Once I replaced the plug WHAM! I picked up 400 rpms and a whole crap load of power. Holeshot doubled and midrange acceleration came alive.

I have mine on a 22ft Bullet bassboat and I run low 90's loaded to fish with an 80lb trolling motor on the nose of the boat.

It's a bad azz motor. :D