6.2L Mercruiser Engine Alarms

[jwaymer]

I recently bought a used 2002 Caravelle with a 6.2L Mercruiser. The previous owner had modiifed it. The Bravo I was replaced with an Alpha I SS (low water pickups, no gear lube monitor) and the captains call exhuast was replaced with straight thru the transom exhaust.<br /><br />The day I bought it, on the test drive it ran great. The first day I had it home and took it out on the local lake, the engine alarms started going off. It has not run without alarming since then. <br /><br />I have replaced the impeller twice (2nd time replaced the whole assembly). I have also taken it to a shop and had the computer diagnosed. The diagnosis was that I had overheating, low waterpressure, knock sensor, and overspeed alarms. The alarm occurs at 4638rpm (everytime). The gages indicate everything normal (tach, water temp, oil pressure), yet I cannot get it over about 4500 rpm without it alarming.<br /><br />I haven't had much luck with the local repair shops with anyone being able to tell me what is truly wrong with it. Any suggestions would be appreciated (if you think I got screwed on this used, modified boat let me know too).<br /><br />Thanks,<br />J

 

[Richard Petersen]

Re: 6.2L Mercruiser Engine Alarms

Call Mercruiser directly. Follow the phone prompt to get to the engine type you have. The LIVE VOICE will help or put you over to a more quailfied person. They will definately send you prints in the mail. Have all the engine info you can get including the stuff on the block and the sterndrive metal tag # numbers when you call them. It worked for me 2 times.--------Be sure to tell them first about the drive changes. That and a loose plug or connection could cause all those alarms.-------late idea. The reason for alarms 1 day later is the "silence jumper" they put in, fell out and it is ringing like it should be, if they could not do the job right.

 

[Limited-Time]

Re: 6.2L Mercruiser Engine Alarms

First off welcome to iboats you will find the help you need here. You need to know just what is tied into the audible alarm system...on my boat only Oil pressure, water temp, and the outdrive oil level are monitored. 4500 RPM could be an over rev. alarm. you should get a manual, that will tell you whats monitored, and also how to trouble shoot the system. There ma be an on line manual available for your power plant. Good luck.

 

[newport dave]

Re: 6.2L Mercruiser Engine Alarms

The beep you are hearing at 4500RPM is the probably an overspeed alarm. You mentioned an overspeed fault, did it have a high frequency count (100+)? <br /><br />It sounds like you have an active fault code that is causing the engine to go into "Gaurdian Mode" and reduce the Available Power to 90%. When you are at 90% Available Power the rev limit is reduced to 4500RPM.<br /><br />You didn't say if were those fault codes were in the freezframe memory or if they were active faults. An active Knock Sensor fault will cause a reduction of available power to 90%. That may be your problem.<br /><br />Could also be high exhaust manifold temps, even if the analog gauge on the dash shows normal engine temps.<br /><br />The dealer should have been able to diagnose this.<br /><br />Dave

 

[jwaymer]

Re: 6.2L Mercruiser Engine Alarms

Dave,<br />Thanks for the info. The time it cuts out and alarms is at 4683rpm (exactly 90% of the rated 5200 rpm). The count on the overspeed was 31, stbd overheat - 39, knock sensor - 14, guardian mode was 32 times for 583 seconds. The dealer did not tell me if they were active or freeze frame.<br /><br />I just got back from the lake for another test drive after changing the spark plugs and cleaning the water pressure sensor. The alarms still occur. I noticed alot of steaming from the exhuast, even though the dash gauge showed normal.<br /><br />Additional info, I have an intermittent beep that beeps twice every 2 minutes or so. This is NOT the gear lube monitor since it has been taken off. I also verfied this by jumping out the wires for the monitor and it caused a much faster pace intermittent alarm.<br /><br />Do any of you think that the low water pickups on this Alpha SS are not suitable for a 6.2L engine, meaning they can't supply enough water?<br /><br />The local marina that I launch at (not the one with the computer) has offered to let me try an Alpha with normal side pickups to see if it cures it. I like wrenching on things, but would rather avoid this if someone has info on the low water pickup's ability to supply water.

 

[newport dave]

Re: 6.2L Mercruiser Engine Alarms

The key here is to find out which fault code is active and causing the reduction of Available Power.<br /><br />The starboard side manifold high temp fault may be the problem and the excessive steam in the exhaust suggests that there is a problem there. Does the riser feel real hot? It should be about 110-120 degrees at idle and you should be able to touch it with no problem. The fault will be active when the temp reaches 212 degrees.<br /><br />I think it is possible that the Alpha drive inlet may not flow enough. Is there still a pump in the drive? But why would it run great with no alarm the day you tested the boat? <br /><br />This is from the 6.2MPI installation manual. Note that closed cooled models need two inlets (don't know if yours if closed cooled or not).<br /><br />

<br />Dave

 

[jwaymer]

Re: 6.2L Mercruiser Engine Alarms

It is not closed cooled. Interesting note though, with the Bravo, it had the engine driven seawater pump. The Alpha has the impellor in the lower unit. I noticed this the other day, that the engine driven was still in the loop. I bypassed it and went strictly off the outdrive's pump. No affect.<br /><br />The day I test drove it, the previous owner pointed out that the risers were "cool" to the touch after running. They are not now.<br /><br />Also, yesterday when I was running it I noticed that when it was cool (just started) that it has quite a bit of water pouring out the exhaust. When I brought it back to the marina it was hot and the water was just trickling out. So what would cause flow to decrease as it gets hot?<br /><br />I'm going to pull the exhaust risers off today to see if something is clogged.

 

[newport dave]

Re: 6.2L Mercruiser Engine Alarms

You may have some debris somewhere in the cooling system. Probably won't be at the risers, but at one of the coolers (power steering cooler, oil cooler, or fuel cooler). <br /><br />You said there was no change when you bypassed the engine mounted pump. Did you pull the pump apart and check the impellor? If the impellor is damaged, the lost blades could be whats clogging the system.<br /><br />Dave

 

[Richard Petersen]

Re: 6.2L Mercruiser Engine Alarms

Check all your coolant hoses for being FIRM when cold. Then check them when hot and the trickle of hot water is on. DO NOT COOK the engine for any test.You may find collapsed water hoses any where.

 

[jwaymer]

Re: 6.2L Mercruiser Engine Alarms

Cyclops - yeah I started taking hoses off yesterday to check for blockages and noticed the very short one with two 90* bends coming out of the fuel cooler to the distribution block is somewhat collapsed (cool). I don't know if this is normal for that hose, but it is not round and feels a little soft.

 

[TilliamWe]

Re: 6.2L Mercruiser Engine Alarms

You are CERTAIN of this?:<br /><br />

The Bravo I was replaced with an Alpha I SS (low water pickups, no gear lube monitor)

<br /><br />Why would anyone do that?<br /><br />That said, shouldn't the Bravo raw water pump have been by-passed? Or would you eliminate the Alpha impeller in the lower unit? Either way, you have a water flow issue. After checking your hoses, remove the thermostat housing & look for impeller pieces there. Then figure out which impeller you actually have operating... the one in the drive or the one on the motor.

 

[jwaymer]

Re: 6.2L Mercruiser Engine Alarms

Tilliam - yes, I am certain of this. I have the original paperwork from when the previous owner bought it. The S/N for the originall drive is a BravoI. The one on it now is definetly an Alpha SS....Why would anyone do that??? - it was for speed. Now the question is, why would anyone buy it (meaning dumba$$ me)!?....it seemed like a good deal at the time. <br /><br />The Bravo was not bypassed, but I did the other day. I am definetly running on the drive's impellor now. One test drvie like this, but still same problem. <br /><br />....tearing off hoses now, still looking for blockages.

 

[jwaymer]

Re: 6.2L Mercruiser Engine Alarms

Cyclops - i tried calling Mercruiser, but they couldn't help - just directed me to a local dealer. What is the number that you called? <br /><br />Also, I just re-read your first reply post. And had to laugh. I didn't catch the part about the "silence jumper", but that thought has crossed my mind - lol.

 

[waterone1@aol.com]

Re: 6.2L Mercruiser Engine Alarms

Just thought I'd add that the beep you hear every minute or two is telling you that there is an active fault code in the ECM. All of the above is good advice. It would help to get a scan tool on this and write down the trouble codes. Also, start at the begining and pull the raw water hose as it comes through the transom. Fire it up on the muffs for 30 seconds and see what your water flow looks like comming from the drive. If weak, pull the lower and inspect the impellor, pump housing and seals.

 

[jwaymer]

Re: 6.2L Mercruiser Engine Alarms

I have all of the hoses off. Haven't found anything. Also, have taken off the thermostat housing and all is clean.<br /><br />I checked the flow the other day coming through the transom and it looked good.<br /><br />Could this be a water circulation pump (engine driven) problem???<br /><br />What scan tool do you recommend? Are these readily available without being a Mercruiser dealer?

 

[jwaymer]

Re: 6.2L Mercruiser Engine Alarms

What should the compression be on a 6.2L?

 

[newport dave]

Re: 6.2L Mercruiser Engine Alarms

If you don't have a restriction, then you have a pump problem of some type. With the dual pumps it hard to say what is happening. <br /><br />The solution? Install a thru-hull pickup like they do for closed cooled models. "Y" it in to the existing engine mounted pump. Disassemble both pumps, make repairs as necessary. No more flow problems.<br /><br />Dave

 

[jwaymer]

Re: 6.2L Mercruiser Engine Alarms

Excellent idea Dave!<br /><br />Thanks for the help y'all. I'll post an update when done.<br /><br />This is an awsome site by the way.

 

[jwaymer]

Re: 6.2L Mercruiser Engine Alarms

Oh yeah, what do you think about trying an AlphaII with side water pickups first (before I drill my hull or transom)?

 

[jwaymer]

Re: 6.2L Mercruiser Engine Alarms

Could this be my problem?<br /> http://pg.photos.yahoo.com/ph/jwaymer/detail?.dir=c66c&.dnm=abbd.jpg&.src=ph <br /> http://pg.photos.yahoo.com/ph/jwaymer/detail?.dir=c66c&.dnm=ac26.jpg&.src=ph <br /> http://pg.photos.yahoo.com/ph/jwaymer/detail?.dir=c66c&.dnm=a9d5.jpg&.src=ph <br /><br />The pictures are of the exhaust manifold and elbow. Whoever installed the elbows used an excessive amount of RTV gasket maker. It appears that it was not sealed everywhere either....maybe water was dumping into the exhuast ports. I wil clean these up and install the correct gasket. Also looks like I will need to backflush the elbow to make sure there are no pieces of RTV clogging it up.