496MAG HO seems down on power for planing.
07-20-2021 | 02:58 PM
#11
Thread Starter
VIP Member
Joined: Jun 2021
Posts: 3,486
Likes: 2,115
From: SW Ohio
Had the boat sitting on the ramp until the drain plug stopped dripping. Have not tilted the boat on the trailer. May have to do that.
Starter seems to be fine. I'll keep an eye and an ear on it.
Thanks. Brad.
Model Machine and Precision LLC
(937)545-8991
07-20-2021 | 03:07 PM
#12
Registered
Joined: Oct 2012
Posts: 2,230
Likes: 536
Underpsi,
It has always been my assumption that these EFI engines couldn't NOT have O2 sensors. Seems like I read a discussion thread a number of years ago where somebody was asking if EFI could be installed without one; if a baseline could be established with the sensor, and then remove the sensor, because of the whole water issue, and the resounding answer was "No". To be honest, I really don't know. This is about 83 steps above my paygrade in the field.
Thanks. Brad.
Model Machine and Precision LLC
(937)545-8991
It has always been my assumption that these EFI engines couldn't NOT have O2 sensors. Seems like I read a discussion thread a number of years ago where somebody was asking if EFI could be installed without one; if a baseline could be established with the sensor, and then remove the sensor, because of the whole water issue, and the resounding answer was "No". To be honest, I really don't know. This is about 83 steps above my paygrade in the field.
Thanks. Brad.
Model Machine and Precision LLC
(937)545-8991
07-20-2021 | 04:09 PM
#13
Registered
Joined: Jul 2014
Posts: 670
Likes: 117
From: Denton, MD
Brad,
Just went through this with a Sunsation 288 at the shop with a 496 Mag HO. May not be your issue but this is how we got it diagnosed and back up after the owner reported lack of power after sitting for three years.
1. Check Voltage - Ensure you have proper levels with key off and key on running. These are CPU driven engines, important to ensure the proper voltage is present for sensors. We installed new batteries anyway at request of owner
2. Check Spark to Verify Coils - Use in-line spark plug tester to ensure spark is making it to plug. We did this test after replacing the spark plug wires due to deterioration.
3. If you have access to the Mercruiser Scan Tool you can complete an injector cycle test to ensure all injectors are firing. We found three injectors that we not operating
4. You can also use the scan tool to perform a Misfire test, the tool will shut down each cylinder for 10 seconds while under load (1500-2000 RPMs in the water). You should feel and hear a difference in power with each cylinder test. If no change in power or sound then you have found the dead cylinder. This helped us further deduce the three dead cylinders.
5. Compression Test - Ensure no damage to cylinders. This is a standard practice for us after sitting for some time or any chance of water intrusion
6. Clean all connections that may have been under water. Standard practice after water exposure.
7. Check fuel filters, pump internals, and fuel pressure regulator. Since the boat had been sitting for three years we replaced the filters and regulator for good measure.
Like I mentioned before, these were steps we took for this particular boat. In your situation I would recommend the following:
Voltage Check, Connection Cleaning, Induced Misfire Test then go from there with the additional tests/corrections as needed. These engines have a good amount of electronics and are sensitive to fuel pressure.
Just went through this with a Sunsation 288 at the shop with a 496 Mag HO. May not be your issue but this is how we got it diagnosed and back up after the owner reported lack of power after sitting for three years.
1. Check Voltage - Ensure you have proper levels with key off and key on running. These are CPU driven engines, important to ensure the proper voltage is present for sensors. We installed new batteries anyway at request of owner
2. Check Spark to Verify Coils - Use in-line spark plug tester to ensure spark is making it to plug. We did this test after replacing the spark plug wires due to deterioration.
3. If you have access to the Mercruiser Scan Tool you can complete an injector cycle test to ensure all injectors are firing. We found three injectors that we not operating
4. You can also use the scan tool to perform a Misfire test, the tool will shut down each cylinder for 10 seconds while under load (1500-2000 RPMs in the water). You should feel and hear a difference in power with each cylinder test. If no change in power or sound then you have found the dead cylinder. This helped us further deduce the three dead cylinders.
5. Compression Test - Ensure no damage to cylinders. This is a standard practice for us after sitting for some time or any chance of water intrusion
6. Clean all connections that may have been under water. Standard practice after water exposure.
7. Check fuel filters, pump internals, and fuel pressure regulator. Since the boat had been sitting for three years we replaced the filters and regulator for good measure.
Like I mentioned before, these were steps we took for this particular boat. In your situation I would recommend the following:
Voltage Check, Connection Cleaning, Induced Misfire Test then go from there with the additional tests/corrections as needed. These engines have a good amount of electronics and are sensitive to fuel pressure.
07-26-2021 | 12:00 PM
#14
Registered
Joined: Oct 2010
Posts: 1,621
Likes: 402
From: Cheboygan, MI
I had a similar experience on my brothers boat. His boat was outside and covered and we had had a week of major rain. We got the water off the cover and towed it to the ramp. When we tried to launch it we noticed we had to back the truck down the ramp further that usual, we just figured it was the slope of the ramp. We idle out and get out on the lake and he could not get the boat on plane. He opened the hatch and I look inside and water is shooting everywhere. I yelled head to shore and beach it before we sink. He hit the manual override on the bilge pump and nothing. While he's heading to shore I checked the power at the switch and the breaker was toast. So while he's driving I rewired the bilge to a different breaker and got the pump working. Fortunately he had some monster bilge pump. We could see that the water was going down so we stopped to see how fast the water was going down and realized the cover wasn't completely water proof and the boat had filled with rain water. It's amazing what 50 gallons of water will do.
I also had a similar situation on my boat. Put the boat in first time in the spring, get it started and warning it up and all of a sudden the bilge pump turns on. Open the hatch and I realize I had forgotten to put one of the block drains back in. Grabbed a spare out my tool box and got it back in and now after I winterize the boat, I put the drains right back in to make sure I don't do that again.
I recommend checking your drain holes, you may have debris blocking them and holding water. I'd also check your bilge pump and float switch. That should have turned on before you left the dock.
I also had a similar situation on my boat. Put the boat in first time in the spring, get it started and warning it up and all of a sudden the bilge pump turns on. Open the hatch and I realize I had forgotten to put one of the block drains back in. Grabbed a spare out my tool box and got it back in and now after I winterize the boat, I put the drains right back in to make sure I don't do that again.
I recommend checking your drain holes, you may have debris blocking them and holding water. I'd also check your bilge pump and float switch. That should have turned on before you left the dock.
07-27-2021 | 01:37 AM
#15
Platinum Member
Joined: Sep 2001
Posts: 5,769
Likes: 150
From: tn
1) loosen plug wires at the distributor. With motor running 1000 rpm in gear (in the water, or backed into water on trailer) lift the wires off the cap one at a time listening to make sure each cylinder is doing the same work. You may have a bad plug wire or 2.
2) small electrodes make the best spark. The only reason to have fat electrodes is so the tip takes longer to burn away. The more exotic and long lasting the electrode metal is, the smaller they can make em.
3) water into the supercharger gets chopped into mist. As long as it is just mist going in your motor, no big deal. It's when water comes backwards from the exhaust into the head that you see problems. Hot exhaust valves just after a hard run tend to snap off their heads when liquid water comes at them from exhaust reversion. That's not what's going on in your case.
4) I would imagine you may have a bunch of trapped water in your hull. With boat on trailer, get it VERY nose-up. Run long rods up thru the bulkhead drains to see if you can get it flowing out the back.
5) you need to at least temporarily put a boost gage on your motor to make sure you are making proper boost. Belt slippage is a common issue on Prochargers. And once a belt slips for a while, it can "glaze" and lose grip. You'd think that a slipping belt would leave black dust, but it doesn't always do that.
2) small electrodes make the best spark. The only reason to have fat electrodes is so the tip takes longer to burn away. The more exotic and long lasting the electrode metal is, the smaller they can make em.
3) water into the supercharger gets chopped into mist. As long as it is just mist going in your motor, no big deal. It's when water comes backwards from the exhaust into the head that you see problems. Hot exhaust valves just after a hard run tend to snap off their heads when liquid water comes at them from exhaust reversion. That's not what's going on in your case.
4) I would imagine you may have a bunch of trapped water in your hull. With boat on trailer, get it VERY nose-up. Run long rods up thru the bulkhead drains to see if you can get it flowing out the back.
5) you need to at least temporarily put a boost gage on your motor to make sure you are making proper boost. Belt slippage is a common issue on Prochargers. And once a belt slips for a while, it can "glaze" and lose grip. You'd think that a slipping belt would leave black dust, but it doesn't always do that.
07-29-2021 | 10:02 AM
#16
Registered
Joined: Jun 2004
Posts: 329
Likes: 1
From: MD
Fellas,
I've got this PowerQuest 280 with a 496MAG HO and a factory build M1 intercooled Procharger. So far, it's been golden. But then, we pulled the ultimate bonehead boater's move and dropper it in without the drain plug. We were out of routine. Don't judge... We got it back on the trailer, but it it took keeping it on at full throttle, plowing around the inlet to the ramp area until the wife could get the trailer back into the water. Luckily, there was nobody at the ramp, so no harm, no foul. After letting it drain, we dropped back in, drain plug in, of course, and headed out for an evening cruise. Upon exiting the no wake zone, I throttled up as I usually would, but the boat didn't want to get out of it's own wake. It took forever to climb up on a plane. A few details... First time with a full load of fuel. First time with this many people (four adults, two of them fairly good size, two small children). typical 496 transom soot seems excessive after this event. Take-off power seems off considerably, even with lighter load (fuel and people). Fuel consumption seems excessive, although this is the first time we've made an extended trip with this boat (and hour or so, one way, at modest cruise speed). Obviously boat seems to run fine once it's on plane. One service shop suggested new spark plugs, which I've done. While the engine seemed to like them, the issue is still there, even if slightly improved (maybe). Old plugs seemed slightly fouled, but not horribly. Center electrode seemed very small, as if eroded, but pics of the Denso plug seemed to indicate they are made fairly small. New plugs, ACDelco 41-983, had much more substantial center electrodes. I've spoken to Mercury. I've spoken to a total of three shops. I've gotten suggestions about the O2 sensor(s) and I've gotten suggestions about a locked open injector. Both seem like reasonable possibilities, but I'm not of the mind to just start throwing parts at it. With the intercooled Procharger, the intake for the engine is actually pretty low in the engine well, and I wonder about ingesting small amounts of water as it sloshed around while the boat was loaded down with the drain plug missing. I have not had a chance to plug into the ECM and see if there are any codes, but I have gotten a commitment from one of the local Mercury service shops to do so. I wouldn't be about purchasing one of these scanners for my own, if they aren't to spendy, but I'm not really sure what to get. My last boat had an old school 454 carb engine. This is my first go with a "smart" engine. Don't know if the attempted sinking, or the subsequent heavy load plowing had anything at all to do with this, but the coincidence is there. That's when the behavior changed and the performance dropped off. While planing, the tach hits a wall at 2900 RPM until the hull starts to break loose. After that, I can put it wherever I want it within it's normal RPM range. While planing, boost gage shows zero manifold pressure at that 2900, which is different from on a plane, where it hits zero manifold pressure at about 3700 RPM.
Thoughts?
Thanks. Brad.
Model Machine and Precision LLC
(937)545-8991
I've got this PowerQuest 280 with a 496MAG HO and a factory build M1 intercooled Procharger. So far, it's been golden. But then, we pulled the ultimate bonehead boater's move and dropper it in without the drain plug. We were out of routine. Don't judge... We got it back on the trailer, but it it took keeping it on at full throttle, plowing around the inlet to the ramp area until the wife could get the trailer back into the water. Luckily, there was nobody at the ramp, so no harm, no foul. After letting it drain, we dropped back in, drain plug in, of course, and headed out for an evening cruise. Upon exiting the no wake zone, I throttled up as I usually would, but the boat didn't want to get out of it's own wake. It took forever to climb up on a plane. A few details... First time with a full load of fuel. First time with this many people (four adults, two of them fairly good size, two small children). typical 496 transom soot seems excessive after this event. Take-off power seems off considerably, even with lighter load (fuel and people). Fuel consumption seems excessive, although this is the first time we've made an extended trip with this boat (and hour or so, one way, at modest cruise speed). Obviously boat seems to run fine once it's on plane. One service shop suggested new spark plugs, which I've done. While the engine seemed to like them, the issue is still there, even if slightly improved (maybe). Old plugs seemed slightly fouled, but not horribly. Center electrode seemed very small, as if eroded, but pics of the Denso plug seemed to indicate they are made fairly small. New plugs, ACDelco 41-983, had much more substantial center electrodes. I've spoken to Mercury. I've spoken to a total of three shops. I've gotten suggestions about the O2 sensor(s) and I've gotten suggestions about a locked open injector. Both seem like reasonable possibilities, but I'm not of the mind to just start throwing parts at it. With the intercooled Procharger, the intake for the engine is actually pretty low in the engine well, and I wonder about ingesting small amounts of water as it sloshed around while the boat was loaded down with the drain plug missing. I have not had a chance to plug into the ECM and see if there are any codes, but I have gotten a commitment from one of the local Mercury service shops to do so. I wouldn't be about purchasing one of these scanners for my own, if they aren't to spendy, but I'm not really sure what to get. My last boat had an old school 454 carb engine. This is my first go with a "smart" engine. Don't know if the attempted sinking, or the subsequent heavy load plowing had anything at all to do with this, but the coincidence is there. That's when the behavior changed and the performance dropped off. While planing, the tach hits a wall at 2900 RPM until the hull starts to break loose. After that, I can put it wherever I want it within it's normal RPM range. While planing, boost gage shows zero manifold pressure at that 2900, which is different from on a plane, where it hits zero manifold pressure at about 3700 RPM.
Thoughts?
Thanks. Brad.
Model Machine and Precision LLC
(937)545-8991
07-29-2021 | 11:09 AM
#17
Thread Starter
VIP Member
Joined: Jun 2021
Posts: 3,486
Likes: 2,115
From: SW Ohio
Guys,
Thanks for all the replies.
I had the ECU read, and we got no codes. Tried doing a cylinder dump, both ignition and injectors, but we couldn't get it to respond. Don't know if it's the tune on the ECM not allowing this function or just that the software on the laptop, that had the function, wasn't properly communicating. All seems good with the engine.
The more I think about it, the more I think it was just excessive water in the boat, even after allowing it to drain on the ramp. After swapping the spark plugs, we took it out for a quick test. While it still seemed sluggish, it was slightly better. The interesting thing was that, upon pulling the boat out and dropping the drain plug, we got a crap ton more water out of it. After being out for about an hour, no rain and nobody in and out of the boat, dragging water in, I wouldn't have expected any at all, so I'm assuming it had to be in there still from the initial sinking attempt. The next time we took it out, a week later, the boat hopped up on plane fairly quickly, even with no trim tab help, which I had been using, while not having to prior to the issue popping up.
I'm really thinking this was a case of kind of a perfect storm of a full tank, excess bodies and a ton of unwanted water in the hull.
Repeat of details....
PowerQuest 280 Silencer
4800lbs dry
496MAG HO w/M1 Procharger and stage 2 Whipple tune
Bravo 28P prop, 1.5 drive ratio.
How much water do you suppose it would take to overload a boat like this?
Thanks. Brad.
Model Machine and Precision LLC
(937)545-8991
Thanks for all the replies.
I had the ECU read, and we got no codes. Tried doing a cylinder dump, both ignition and injectors, but we couldn't get it to respond. Don't know if it's the tune on the ECM not allowing this function or just that the software on the laptop, that had the function, wasn't properly communicating. All seems good with the engine.
The more I think about it, the more I think it was just excessive water in the boat, even after allowing it to drain on the ramp. After swapping the spark plugs, we took it out for a quick test. While it still seemed sluggish, it was slightly better. The interesting thing was that, upon pulling the boat out and dropping the drain plug, we got a crap ton more water out of it. After being out for about an hour, no rain and nobody in and out of the boat, dragging water in, I wouldn't have expected any at all, so I'm assuming it had to be in there still from the initial sinking attempt. The next time we took it out, a week later, the boat hopped up on plane fairly quickly, even with no trim tab help, which I had been using, while not having to prior to the issue popping up.
I'm really thinking this was a case of kind of a perfect storm of a full tank, excess bodies and a ton of unwanted water in the hull.
Repeat of details....
PowerQuest 280 Silencer
4800lbs dry
496MAG HO w/M1 Procharger and stage 2 Whipple tune
Bravo 28P prop, 1.5 drive ratio.
How much water do you suppose it would take to overload a boat like this?
Thanks. Brad.
Model Machine and Precision LLC
(937)545-8991
07-29-2021 | 11:17 AM
#18
Registered
Joined: Nov 2004
Posts: 14,093
Likes: 3,683
From: On A Dirt Floor
When back, did you tiot trailer up as humanly possible in case eater got up frt where maybe not set up to easily drain ? I use a farm jack, others use steep hill near the house, just to do once in a while. I know one person who forgot his drain plug and smartly brought it up nearby shallow water beach.
Glad it all worked out for you ! :thumbs
