Trouble starting 496 Mag
 

Hello all. Newbie here, with a few questions.

I just purchased a new to me, 01 Baja 272 w/40 hrs on a 496mag. I took the boat out for the first time today, and ran into trouble. The boat fired up on first try, and ran smooth at idle for about 10 min. When I backed away from the docks, it began to stutter/miss as if it were running out of fuel. I assumed my fuel gauge was faulty (reading 1/4-3/8 tank) and refueled the boat. Once back at the lake, the engine still would not start, and I nearly drained my battery trying.

Is there something I'm missing? Perhaps a fuel shut off valve? Air in my fuel system? Or something else all together?

What is the standard manufacturers warranty for Baja/Mercruiser? Is my boat covered?

I appreciate any input/adivce you all may have to offer.

Joe

Since you just purchased the boat, did you buy it from an individual or dealer? Dealer-warranty? Individual-call and ask about previous issues? Wish I could help further. Stick around and you'll get some good advice here on this board.

Welcome aboard and check out the Baja section!

The Merc standard warranty is 1 year, but can be extended to 5 years(more $$). If you bought it private, did you receive any extended warranty paperwork? Otherwise, it's probably out of the warranty period.

Anyway, have you replaced the fuel filter. Maybe some bad gas in there or a gummed up filter. Can you hear the fuel pump running when you turn the key from 'off' to 'run'(not start, just run)? Could be a bad pump.

Thanks for the quick replies.

I bought the boat from an out of state dealer. No indication of warranty extended or otherwise. Other than them assuring me the boat was in great shape/working condition.

I have not replaced the fuel filter. But will do so ASAP if that's the culprit. I can hear the fuel pump each time I turn the key. Is there anything else which could be causing this problem?

1. Fuel filter is the most probable item especially if it sat during the winter with little or no fuel which would result in heavy water build up.
2. If you boat has one, the fuel shut-off at the tank (most boats do not have them since the CG does not require them anymore).
3. Replace all gas with fresh.

There really isn't much more to break so if that doesn't work then get a Merc mechanic to run a diagnostic.

when engine running @ dock would it rev in neutral?
sorry for this basic one but was your kill switch in place after stalling?

Formulafastech: The engine would not even try to fire after it died the first time. I have not checked for spark yet.

Vyper340: I just picked up a new fuel filter, and I'm headed out to install it now.

28SS: Nothing is too basic for me right now. LOL
The engine would rev in neutral, and the kill switch was in place.

It seems the problem will be harder to diagnose than I had hoped. Before installing the new fuel filter, I tried starting the boat just to see what would happen. The boat started instantly. It continued to run smooth for approx. 10 minutes. It then began to run as if it were starving for fuel, backfired, and quit. The boat would not restart after this. I installed the new fuel filter, and tried again. Nothing.

I gave the engine 3 hours to cool, on a hunch that it would start again. It did, ran for 10 min, then same story.

My theory is that after 10 minutes or running (open loop), the boat begins to reach operating temperature (140-150 degrees) and then the computer (closed loop) is shutting the engine down.

Does this sound right? Perhaps a faulty sensor/sender? Has anyone here had this problem with a 496 mag before?

I don't see what alternative I have, besides taking the boat in and having it scanned for codes. Hopefully somone here will have another solution.

01 272 boss,

I did a search on the bleow site for any service bulletins that describe your problem. Unfortunetly, nothing was listed that fit your explaination of your trouble. But, here is the link for the site anyway. You or others may find it useful for something someday.

http://www.bravodrives.com/bulletins_main.html

checkmate454mag: I appreciate your effort. I'll check it out, maybe I can learn something.

I don't know if this information will help solve the problem, but I learned a few more things tonight.

I was going through the boat, checking fuses, tightening loose bolts, etc. I found one blown fuse in the engine compartment, and decide to try starting it again.

It had been nearly 5 hours since the last time I started it, so I knew it was cool. The engine fired right up, but quit in less than 3 minutes this time, at approx 120 degrees. Since I was watching my gauges the whole time, I noticed that when it began to stall, my tach quit working. Correct me if I'm wrong, but this should indicate that there is no spark.

Formualfastech: To be honest, I'm not sure what the fuse is for yet. It's a 2 amp 250v fuse located near the battery. The fuse did not blow again, and the fuel pump primes with or without the fuse.

The engine does not quit instantly, it's kind of a slow process. Stutters, back fires, fires, stops. The tach needle completely drops each time it coughs.

This sounds very odd. At first, I would swear that it is fuel related, but now it seems more and more like some kind of ECM related problem. No way to diagnose that without a scanner.

I agree with BD, it sounds like a fuel related problem. Just as you thought the first time, it sounds like it is running out of fuel for whatever reason. I am unfamiliar with the fuel delivery systems of this engine and can't really make an informed diagnosis.

I beleive the problem is with the coil.
if eng will rev in neutral but not under load
had eng that I replaced fuel pumps high/low prressure
because of same problem same symptoms was coil
coil gets warm and voltage drops i.e sputter/die coil cools
off and is fine till warm.
hope this helps

Cam Positon Sensor?

I agree with Kentz. In fact, I was out on the lake with a friend who had twin 496 Mags when his cam (or crank I'm not sure) position sensor was giving him problems on one side. It turned out to be faulty. His would start, backfire and run (if thats what you want to call it) up until the time he tried to plane then it would quit. He had some success in disconnecting and reconnecting it but ultimately it would die again crossing the lake. It's located on th top of the bell housing. It's a couple of wires terminating into a weatherpack connection.

Your right!, I think it might be crank sensor, the cam sensor is what quite on my PSD. i

Gotta admit, you guys are pretty good!

I took the boat to a Merc repair facility this morning. He ran diagnostics on it, and called me with the results.

#1 The computer is throwing lots of codes which are associated with the problem.

#2 He said he's not 100% sure yet, but its either the crank position sensor, or the camshaft position sensor.

#3 He also said the computer shows 15hrs use on the engine, but the hour meter shows 47hrs???

He's calling merc tech support right now to see if they have any ways to confirm which it is. I'll post with the results.

I just thought of one other thing that has failed on these engines (including 496 HO). The crank position sensor fails and won't allow the boat to rev under load. Once it fails it won't restart for some time but when it does it will run at idle but not under load.

The sensor is about the size and dimension of a cigar and it's located on the rear of the engine where it attaches to the transom and drive. It's an easy and inexpensive fix for a Merc mechanic. Unfortunatley it does not show as a fault when you run a diagnostic. The part cost about $50 and it's less than an hour to install, adjust and test.

Good luck.

Just picked up my boat, and all is well. It turned out to be the crank position sensor. Imagine that, a little $60 plastic sensor causing all this trouble. lol Thank you all for your help and advice.

Now I finally get to take out my new boat!!

Good call vyper 340!

01 272 go have some fun!

I was too late reading this but I was going to throw out the crank sensor too, I believe that there was a recall on this last year

Here are the two threads from last spring:

http://www.offshoreonly.com/forums/s...t=crank+sensor

http://www.offshoreonly.com/forums/s...t=crank+sensor

I just read the post and I immediately thought of you Vype340 and your crank sensor problem, but I see all is well now. With the new 496's they are so wired that anytime you have a problem remotely sounding familiar to this one it's gonna be one of the sensors...

01 272, I wold check to see if your serial number coincides with any of the 496 recalls that came out immediately after they started hitting the street. These include but are not limited to the fuel rail and the manifold water bypass adapter that corroded away on several motors causing water to pour into the bilge...

Reckless288: They found 3 other recalls on my engine. 1 involving the fuel rail, 1 on the manifold, and one involving the alternator. All three have already been corrected.

I finally got to enjoy my boat yesterday. What a ride!! It's everything I've always dreamed it would be. I have a new question for you guys regarding prop selection. My boat has an ss 23 pitch prop. The boat only reaches a max RPM of 4300-4400. If I were to change props, which one should I choose? 21,22?

01 272, Not so fast there!!!!! That 496 mag should turn a 23" with no problem to 4800-4950 if your trim is anywhere near. Make sure you are opening fully at the throttle. The rpms you sited is way low for that motor and prop.

Make sure your are trimming correctly! My friend has the same boat and same motor and he sees 4600-4900 consistently with his 496 MAG HO!!

Do you have the HO?

YES!

I was going to say the same thing. That engine/boat combo should be turning that 23"P prop no problem to about 4700rpm. How was the boat loaded?

272/275's with the 496MAG(375hp) are equipped with the 23P.
Even 25 Outlaws(a heavier boat, same size) with the 375hp engines are turning 23P MP's up to 4700rpms.

Yes.

I have an 02 25 Outlaw with 496 Mag 375 HP spinning a 23 pitch prop at 4700 to 4800 rpm no problem. 64.1 mph on GPS. Your 272 should have no problem doing that.

Hey guys, I apologize for the late reply.

Sounds like you guys are on to something, I cant wait till this weekend to give it another try. In terms of trimming out the motor, to be honest my gauge does not work. We found a broken rotor inside the trim sender and I'm waiting on the part to fix it.

However, I did trim the motor to what I "believed" to be a reasonable level by watching my speed. I was able to get the rpm's up to 4500, and a max speed of only 58mph. This was with 1/4 tank of gas, myself (165lbs) and two women (less than 110 each) in the boat.

I'll also look into the throttle issue to make sure it is fully opening.

Trim that Mutha' out until it starts to porpoise, then drop it back in just a bit. You don't need no stinkin' indicator on a single ;)

Boss, keep us posted. Something is definitely amiss. You should be getting more rpms and speed. I had a 272 with a 502mag that would run 70speedo and 68gps. You should be close to 65speedo for sure.

One more thing, those speeds were with a 23 Mirage. I switched to a 24 Bravo which gave me much better performance all around, but I did loose a bit off the top end.