3.0 Promax problems.

[Jonesy23]

Hello, I am new to this forum so I am hoping I am posting in the right place. I bought a 2000 31 ft Cobra predator a few months that has a pair of 2001 300xl Promax with Sportmaster lower units with about 250 hrs on the motors. I know its not a bass boat but was hoping you guys could help me out. I will put the link to another forum that I had been on discussing my problems with, it will be easier than trying to got through the whole story. I greatly appreciate and help or feedback.
http://www.screamandfly.com/sh...e-low.

[EuropeanAM]

Welcome to BBC!

Since both engines are experiencing the SAME problem- it's something COMMON to both engines.

I would strongly recommend starting with the SPARK PLUGS. You should be running ONLY Champion QL77PP plugs- I'd recommend STARTING at .030" gap (I know that's not what you've read... but your engines MAY perform better- some find that .035" is helpful).

Fuel quality and delivery are another area to look at, if changing the plugs doesn't help.

I wouldn't sweat your compression readings. We often find the 300X engines with compression substantially higher than the "original OEM Spec".

Feel free to stop back for further assistance if needed.

[Nikon Man]

[b]Jonesy,

Don has touched on a few of your questions and I agree with him.

Here's your S&F post and my answers <u>(underlined):</u>

I'm new to the forum and I recently purchased a 2000 Cobra Predator 31ft with a pair of 2001 Promax 300x.

##My first question is about compression, I had the compression check done during the survey with myself and the seller present. All plugs removed and the throttle at full, both motors numbers were between 143 and 150 psi. I know this is within 5% but are these numbers too high <u>(NO)</u> ?

##I have read some post that these motors should be around 135 <u>(DEPENDS ON HOT, WARM OR COLD CHECK).</u>

##Next question is, the motors have 120 deg thermostats and both motors run at 120 deg. are these temps too low ? <u>(NO THEY ARE CORRECT)?</u>

##My main question is, I had the boat out for only the third time this past weekend and had only myself and my wife onboard, I could only get the motors to turn about 5300 rpm's. The motors seemed to run good without any hesitation, I have jackplates and trim tabs as well as the normal trim of the motors. I trimmed up until my water pressure started to drop below 12 psi or until the steering got real tight, trimmed down, lowered motors and could not get over 5300 rpm, I was only hitting about 65 mph. I contacted the previous owner and he said it would turn about 6500 at about 75 mph with the props that are on it. The props are Bravo 1's 4 blade, labbed 24 pitch. Both motors were running at the same rpm's. The plugs are the cheaper ngk replacement for the champions and were new prior to me buying the boat. I am going to try a new set of the more exspensive ngk's next weekend <u>(ONLY USE CHAMPION QL77PP @ .030-.035 GAP).</u>

I have changed the fuel/water seperators on the motors and the boat has another set of Racors in the bilge that were changed also. Do these motors have another filter inline? (EFI PUMPS HAVE A SCREEN ON THE BOTTOM)

##The motors pull from seperate tanks and I have put about 40 gallons of 93 octane in each tank along with a bottle of Restore. I am hoping the plugs help and I will play with the trim some more but max rpm's as listed on the motors is 6800, I am a long way from that. An old data sheet from the manufacture says the boat with these motors should run 83 - 88 mph, mine has a t-top but still. Any advice or thoughts are greatly appreciated.

Since both are running the same RPM's then it sort of falls in to the fuel system or set up all else being equal. Go over all the fuel hoses from top to bottom, hoses have been known to de-laminate internally with the E10 fuel he have these days (been there & done that). Otherwise look at your set up again and verify everything. Since previous owner made a statement on speed & RPM's based on that same set up and you didn't (I assume) go out and witness said speed & RPM's, it may have never really happened, it's just something to question and think about............. Good luck

[Jonesy23]

Thanks for the replies. I had put the Champion plugs in and they ran good the day I put them in but the next day the motors would not idle and the plugs were fouled. I cleaned them up and will re-gap them and try again . I will also check the fuel lines and was thinking about sending the injectors to Bracato (sp). Any other thoughts about what may be causing my issues? I hit 70 mph last weekend at 6200 rpm but could not get the motors to rev any higher than that, my props are labbed 24 pitch Bravo 1's, I am thinking I should be able to turn a much bigger prop. Also, these boats are known to hit speeds close to 100 mph with these motors and should be getting over 2 mpg at cruise, I get 1 mpg. Any chance I need reed valves?

[Nikon Man]

The possibility of reeds is not out of the question and would be worth looking into at a last resort. How's your idle, if it's good than I wouldn't suspect reeds and I surely wouldn't think both sets are bad......... There's just something very fishy (no pun intended) about this especially since it effect both motors.............. hummmmmmmmmmmm.

Did you test drive the boat before you bought it and witness the claimed speed & RPM's ?

As for cleaning & flowing your injectors, send them to Don. Not saying Tony is bad, just saying Don eats, sleeps and breathes Merc's, and being that he's a Merc Dealership, he's the best in my book for an honest cleaning and flow, trust me you'll be very pleased with the service you'll get from Don @ European Marine, just look at this section that Don supports on his own free time and the help he's given to us all over and over again.

[Jonesy23]

I did a sea trial along with the surveyor but I asked the seller to not run wot as the surveyor would record max speed and at the time I was undecided which insurance company I was going with. A few of the insurance companies wanted a copy of the survey. We did hit 65mph before we turned the gps off and went quite a bit faster afterward so ?? The issue is the poor fuel burn numbers as well as not being able to hit 6800 rpm (max). The seller said when he got the boat it had 28 pitch props on it and ran terrible so he got the labbed 24's. Perhaps this was an ongoing problem and the boat use to run good with 28 pitch props but due to lack of performance needed to go down to a 24p and now the 24p are not hitting max rpm?? Just a theory.
I have seen test date of this same boat with 225 hp Suzuki motors with 29p props with a top speed of 77.5 mph at 5900 rpm (independent test) With a cruise of 47 mph at 4000 rpm at 2.26 mpg and at 4500 rpm was 60 mph and still getting 2.26 mpg.
My idle was good when I got the boat but was terrible after some use because the plugs were fouled so I am not sure what bad reeds would do to the idle. Would the bad reeds cause a bad idle due to running rich or would they automatically cause idle problems?
I am new to high hp outboards so I am a little clueless as it pertains to this.
It really doesn't matter to me who cleans the injectors, I said Bracato because thats who the guys on the S&F forum rave about. Really price and turnaround time would be a deciding factor.
As

[EuropeanAM]

We'd be more than happy to clean/flow/calibrate your injectors.

This particular injector is NOTORIOUS for high-RPM problems- ESPECIALLY if there's EVER been moisture in the fuel system.

Our equipment is SPECIFICALLY designed for the injectors utilized in your Mercury engine. For information, or to download a Service Request Form, visit:

http://www.europeanmarine.org/injectorservice.html

PLEASE... whoever you send them to: Make sure you NUMBER your injectors (corresponding to the position they are in... and the engine they're mounted in). A permanent marker is a good choice- we'll etch the corresponding numbers during service (safely).

[Nikon Man]

If it were me I'd start by letting Don clean the injectors, it's a good investment to know there good to go and it's easier than taking the intake off for reed replacement, which may or may not still need to be done. But the injectors would be where I'd start first....... I also sent you a "IM".

By the way, as for numering the injectors...... DO NOT USE METAL STAMPS AND A HAMMER TO NUMBER THE INJECTORS . If at all possible use a vibropeen marking pen to lightly etch the numbers onto the injector body, <u>(use small numbers as I'll explain later),</u> if that's not available a good high quality perm. marker.

When you get the injectors back some maybe renumbered because of the flow capability and would be better suited in another location, as an example o'l #6 is now the new #2. If that's the case, lightly re-etch the new numbers onto the injector body as received and "X" out the old number, that's the reason for using small numbers as the numbers may changed after cleaning & flow.

And yes, bad reeds will cause, poor idle, poor mileage, and reduced power, but again highly unlikely that both sets went bad together......


Modified by Nikon Man at 6:15 AM 10/5/2011

[kllr bee]

Have you verified that the throttle is opening the motors to wide open. Gap the champions to .035. This sounds like a salt water boat so the throttle position sensors may be messed up. Also if one motor is running bad it could be holding the other motor back.
Richard

[frknu]

Jonesy,
Dont know if this helps, or if you fixed your problem.?
But had a similar kind a issue with a PM 300 (not x)
Thing was, engine was idling and running sorta good on low to mid Rpms but when trying to rew the engine it just didnt want to go further than ca.4500-5000 RPMs. Just like a rew limiter kickin in or something.. As engine was used (not by me before) just been sittin around for a while we didnt know what it was.
-whent trough the complete fuel system, (as sympthoms was as not to get fuel) when that didnt help we could rule out any fuel issues. So only thing remained was electrical related.
After checking almost everythin else we tried with disconnecting the "shift interupt switch" (Shuts off 1/2 engine, or somethin, while shiftin to save gearcase)
--&gt; Took it for a test run and whoala, 90mph.! ,) Obviously the switch kikked in for some odd reason while rewing upp(maby vibrations)..? Anyway on the PM this sits under the Gear shift linkage, suppose 300x has the similar? just disconnect the 2 wires going to th switch n try..? (watch out for you gearcase tough)

-So this all before I blew my engine earlier this summer,, running lean
Now completely rebuilt, but still need to figure out some strange fluctuating rpm readings.. peraps trigger related issues..?

-Fred

[EuropeanAM]

Welcome to BBC, Fred!

I'd encourage you to open another thread on your engine to discuss the fluctuating RPM's, ESPECIALLY since you commented on a lean running condition causing a powerhead failure.

Be sure to indicate whether or not your injectors were cleaned and FLOW TESTED... very critical. Also indicate FUEL PRESSURE at idle, mid, and WOT (as well as whether or not pressure HOLDS after keydown).

Good point on the shift interrupt.... some had a different setup (older models such as yours).

[frknu]

Thanks Don,
I'll probably open a new thread once I got some new parts fitted n tested.
Fuel injectors were cleaned and flow checked tough, not to have any issues..
One thing I did noticed while re assembling was, injector connectors might not have been connected correctly, prior..?! and reeds (carbon) all beaten up..
Fuel press seamed to be in good shape in spec on Idle n Mid RPM, alltough didnt take the gauge out again once got engine running (big mistake) ,/

-anyway I'll get back to you guyes once I got some new figures on the engine..

P.s. great boards here

-Fred


Modified by frknu at 2:01 PM 10/25/2011

[Jonesy23]

So I finally got some work done on the boat. I had the injectors cleaned, raised the motors, put the champions back in and opened the gap to .30 and de-carbed again. I took it out last weekend and no change in how it ran, in fact I think it ran a little worse. So I took it to the mechanic and he hooked the computer up and the starboard motor has multiple codes for the map sensor. Would a bad map sensor explain my issues? No codes on the other motor. He is going to hook up the computer while running it this time to see if there are any other issues after he does a compression check and do a fuel analysis.

[EuropeanAM]

Jonesy23:

YES. The Map Sensor is the "Density" sensor for a Speed/Density Injection System (that's what your engine operates on).

Without it... the ECM has to essentially try to assign a default value (or if the problem is with appropriate vaccum supply, it may actually THINK you're at WOT all the time).

Start there... preferably by first confirming that the MAP sensor is connected to continuous MANIFOLD VACCUM (it's possible to mix up the connection points on these, BTW).

[Jonesy23]

Well the mechanic cleared all codes and could not get the map sensor to re-code so he is thinking that it may be an old code or is intermitten. However, it turns out I had two bad coils on that motor, they wern't firing at all. He also said most of the plug wires were arcing out the bottoms of the boots. So he replaced the coils and all plug wires on both motors and all appears to be good. I am taking it out Sunday and am anxious to see what having all cylinders firing feels like. Thank you all for your help, especially Don.

[EuropeanAM]

Be sure to report back after you've had a chance to run them.

A couple cylinders down (due to no spark) will DEFINITELY have an adverse affect on performance!

[Nikon Man]

Jonesy,

I'm hope'n you got it all taken care of now. Kinda weird that both motor took a crap at the same time though, that's still kinda puzzling.......but all that matters now is that it's all good on both now........

[Jonesy23]

Well, maybe I spoke too soon. Took it out Sat and the first issue was the Smartcraft gauge on the starboard motor is no longer working. It gets power and turns on and has all the menu's but does not give any info, not even hours. Went ahead and ran the boat, the smartcraft still beeped when I turned the key so I figured it was still operational. Starboard motor pulled stong, big difference from before, hit max rpm of 6800 with throttle to spare (hoping for bigger props once i get everything running right). However, the port motor would still not get over 5800 rpm. The bad coils were both on the starboard motor but both motors got new plug wires. Took it back to mechanic same day. Talked to him today and he says the gauge went bad, was a coincidenc, says he switched the plugs from one motor to the other and it worked fine on port gauge and no info on starboard gauge from port motor. Hooked computer up to port motor and no codes, he checked for spark coming out of coils and all was good. He is thinking its a bad plug somewheree on that motor. Keep in mind that that motor has never turned over 6000 since I got it even after the new set of Champions. So now I am operating under the assumption that a new plug was coincidentially bad and my only option is to swap plugs from the other motor to see. Any thoughts? Anyone have options for the gauge, dont have the extra money right now to get a new one. Am thinking of looking for a used one or see if there is an option for a new single unit that works both motors, to buy in the future.

[EuropeanAM]

Plenty of "Options" in the Smartcraft area... a good starting point would be to have a picture of your current "defunct" instrument (or better yet, a picture of your dash).

Spark plug inspection on that port engine would be a good starting point, as well as all the other "basics" (Compression, spark, fuel quality-pressure-delivery).

Monitor MAP SENSOR, perform a sweep test of the TPS to confirm it's operating properly, and if those check out ok, check the reeds.

One other common item: FLOODING or RESTRICTED INJECTORS.

[Jonesy23]

Well, no luck with the plugs. I swapped from one motor to the other, starboard still runs great, port not so great. The mechanic did a fuel sample and all was good, did another compression check and all good, no codes from computer, he did a spark test and all coils are working, he says the computer says the motor is running at 100%. Both motors fell about the same up to about 4k rpm then the port stats to lag behind. The mechanic really has no other suggestions other than more diagnostic time, I cannot continue to pay for diagnostics with no results. I just had the injectors cleaned before I took it in. Any thoughts on the next step in order of most likely to least? I am thinking of just swapping parts from one motor to the other until I find the problem. Do these motors have O2 sensors? I can check the reeds but am not seeing any idle issues. Map code was on the starboard motor and has not re-codded. The port motor still seems to be running rich, it smokes more than the other motor at idle. Thanks again for any help.