scoflaw
Well-Known Member
- Aug 10, 2011
- 6,395
- Boat Info
- 1999 Powerquest legend 260 sx 502 mag
2005 Baja 242 islander 496
- Engines
- 502 mpi Bravo 1
496 mag B1
Yabba dabba doo
Absolutely frustrated with this Mercruiser engine
- Thread starter Hoplite808
- Start date
Sheesh John - It sounds like you want him to move over to carbs?I suppose we can entertain ourselves for the next few weeks as the injectors are being serviced.
In regards to the heads and a cam.....nope. 120 psi compression won't care if it is a carb or EFI. It is an old and tired engine that hasn't run right for some time. We sit back in the contiguous 48 States and it is easy to get parts, diagnostic equipment and help. Some places that just is not true. Most people simplify when they don't have access to those things.....not double down but he owns the boat.
At least Fred Flinstone's car worked.
If a carbureted engine sat with old fuel in the bowls, jets and accelerator pump, emulsion tubes, and wet air in the air bleeds the issues would be similar and we'd be trying to talk the poor devil into fuel injection. Most folks are just as technically challenged properly setting up a carb as they are with fuel injection.
There are more fuel injected engines in boats these days by a long shot - they've only gotten better but vastly more complex than what he has now. If it starts and runs albeit poorly then his issue is 99% assuredly neglected fuel injectors. Worse yet the ethanol carnage on the older fuel injectors can't be overstated. The fuel must be treated or else. He seems to be confident the basic engine is solid and not the issue - I would tend to agree, at least from the information in his cylinder head thread. I do agree that the engine harness needs to be gone over and every connector inspected, cleaned, and sprayed with a corrosion prevention. Intake manifolds for carb's on a Gen V or VI engine is a performance manifold as GM didn't really produce any; so now he is into a rather costly conversion far exceeding what someone said around $1000 - more like 3 or 4K. Can a new marine distributor curved for that engine even be obtained these days for carburetors? It seems the poor guy can't get his head around the fuel injectors being the most probable issue at this point. More concerning is if the used Ebay injectors he acquired and tried to use were Peak and Hold, he might have really damaged the ECM. He did say that his resistance measurements were not in spec on them which is rare on an injector.
Hoplite808
Well-Known Member
- Jan 11, 2022
- 507
- Boat Info
- 1996 Sea Ray 270 Sundancer
- Engines
- Mercruiser 7.4 LX MPI EFI (Gen. V)
I suppose we can entertain ourselves for the next few weeks as the injectors are being serviced.
In regards to the heads and a cam.....nope. 120 psi compression won't care if it is a carb or EFI. It is an old and tired engine that hasn't run right for some time. We sit back in the contiguous 48 States and it is easy to get parts, diagnostic equipment and help. Some places that just is not true. Most people simplify when they don't have access to those things.....not double down but he owns the boat.
At least Fred Flinstone's car worked.
Yes, Hawaii is a special place where we are 4 to 6 weeks away from everything and shipping costs as much as the parts themselves.
Scott215
Well-Known Member
- Jun 4, 2022
- 2,204
- Boat Info
- 2006 215 weekender 5.0 mpi
- Engines
- 5.0 mpi alpha 1 gen 2
I really want to see this get figured out. I love mpi. I don't touch my throttle at all when I start my boat. A 5.0 mpi. Just let it prime and it fires right up. I have spent thousands on a boat that I just bought last year and know the pain of thousands of dollars going out. I wish I could help point you in the right direction
Hoplite808
Well-Known Member
- Jan 11, 2022
- 507
- Boat Info
- 1996 Sea Ray 270 Sundancer
- Engines
- Mercruiser 7.4 LX MPI EFI (Gen. V)
The MEFI1 ECM will only give me trouble codes and little other data even with the most expensive tool. The repair manual I have details a procedure for which to read said codes with a jumper lead and a continuity tester. Currently my engine is not throwing any codes except for code 12 which means the ECM’s self test says it’s working within parameters. Please explain why I need an $800 tool to tell me what my $10 volt meter already does. Also the gimbal bearing had failed and needed to be replaced. I know this because it sounded like a midget had become trapped in the transom with a hammer at one point. When I did the haul out for this repair I found severe damage to the leg that the previous owner had not disclosed so the safest thing to do was install a rebuilt one in its place. This was literally the only repair I could find a professional mechanic locally to assist me with. During the sea trial when I bought it the mechanical issues never presented themselves. Although to be fair we didn’t push it hard during the sea trial. That happened later after I completed the purchase and then everything seemed to fail at once. The gauges I have tested and repaired any wiring issues and know for a fact they work and are accurate now. I did not know how old the impeller was and the circulation pump showed signs of wear. All of that and the thermostat were changed because those are preventative maintenance items anyways to keep it running well. The exhaust manifolds I found cracks on when I removed them so I replaced them. Fun story, porch pirates stole the replacements twice which of course delayed my receiving the replacement parts for months and tripled the cost for me as well. The IAC and other sensors are also relatively inexpensive and the troubleshooting index in the manual indicated they might be the issue. I also found no compression at one point and found that sever valves had seized and bent the push rods. I pulled both heads and had them repaired and resurfaced at a machine shop. The issue with the valves was because mercruiser and General Motors in general went cheap for a while and came up with a valve set up they would expedite assembly to save a few bucks of labor. Unfortunately it leaves you with no wiggle room in the tolerances with the valves. The resurfacing and reseating of the heads and valves changed the geometry just enough that the valves would be held open when I would torque the retaining bolts down. I had two choices then. Spend another $2000 on new heads and gaskets or $200ish on a kit that would convert the valves to adjustable. Making them adjustable worked fine and the valves are no longer being held open. The ignition components I replaced are preventative maintenance items as well so no diagnosis needed there to determine to change them. The fuel system I was able to acquire the proper adapter for the fuel rail and found low pressure so I first changed the mechanical pump as the old one had a fair amount of surface rust on it. The gauge still showed low pressure so I found a kit to rebuild the vapor tank and replaced the electric pump in it. Pressure then returned to normal. The compression in the engine per the repair manual I have says 125 is acceptable. There is no scoring or damage to the cylinder walls or pistons and there is no evidence of oil intrusion into the combustion chamber or excessive blow by into the crankcase when running. The spark plugs show me no signs of lean or rich and none show signs of oil. I hope this helps explain sufficiently the diagnostics performed that led to most of the work I’ve performed so far.
scoflaw
Well-Known Member
- Aug 10, 2011
- 6,395
- Boat Info
- 1999 Powerquest legend 260 sx 502 mag
2005 Baja 242 islander 496
- Engines
- 502 mpi Bravo 1
496 mag B1
So what's your next move?
@Hoplite808
You wrote that you have issues with an engine failing to acclerate the boat past 2000rpm,s - now you say it has beyond that issue problems everywhere . Cracked manifolds , shot gimbal , worn outdrive , bent push rods , scorched impeller pump etc.
Are we talking about an engine struggling to rev past 2000 ( where changing the alternator as trouble shooting is silly nonsens ) or are we talking about virtually anything worn or shot ?
Help yourself to get help here and clarify as good as you can what exactly you did , what parts you changed for what reason and where you got these parts .
Regarding compression : imho 120-125 might open room for a discussion if the engine misses 200-300rpm on top end but no if it struggles to rev past 2000 . I agree the compression is ok , the engine maybe a bit tired but acceptable . And it depends on the gauge and your procedure ( wot during testing ?)
Regarding IAC : iac might be an issue during starting and idle , it has zero effect at 2000rpm and above .
Regarding your 10$ voltmeter ? It shows if your alternator is charging or not Why did you replaced it?
You wrote that you have issues with an engine failing to acclerate the boat past 2000rpm,s - now you say it has beyond that issue problems everywhere . Cracked manifolds , shot gimbal , worn outdrive , bent push rods , scorched impeller pump etc.
Are we talking about an engine struggling to rev past 2000 ( where changing the alternator as trouble shooting is silly nonsens ) or are we talking about virtually anything worn or shot ?
Help yourself to get help here and clarify as good as you can what exactly you did , what parts you changed for what reason and where you got these parts .
Regarding compression : imho 120-125 might open room for a discussion if the engine misses 200-300rpm on top end but no if it struggles to rev past 2000 . I agree the compression is ok , the engine maybe a bit tired but acceptable . And it depends on the gauge and your procedure ( wot during testing ?)
Regarding IAC : iac might be an issue during starting and idle , it has zero effect at 2000rpm and above .
Regarding your 10$ voltmeter ? It shows if your alternator is charging or not Why did you replaced it?
PlayDate
Well-Known Member
Actually I really like modern fuel injection. Every go boat I play with junked the GM EFI systems and went with Fast XFI a long time ago which are super easy to calibrate, test and use. I just take a step back and look at the situation he has which is really complicated by where he is. In the absence of local help he has done a lot of solid work sorting through the boat and its systems.
It isn't fair to second guess every decision that he has made.....yet here we are. Other than seeing him enjoy his boat on the water......it appears we want to push him to make a decision that he isn't comfortable with yet.
Keep in mind he already dropped $300 on a set of Ebay injectors (not to mention all the hours working on it) and the engine did not even start. So there is that and that concerns me as well. Sure an entire batch of China injectors could be bad.....or maybe they aren't and something else is the issue. For the record I have used Ebay injectors before and never seen an entire batch that didn't work so that is rolling around in my head and I would guess the OP's. That gives me pause about telling someone to drop a $1,000 on injectors when I can't put my hands on the engine.
It doesn't help to minimize or criticize what he has done or act annoyed that he hasn't acted on our suggestions.....that is not helpful and usually shows up on CSR when a thread goes over a 100 posts.
I want to see him enjoy his boat as I believe most of us want him to do. So the ball is in his court. There is only so much you can do remotely.
PlayDate
Well-Known Member
Exactly. Fortunately putting the old ones back in at least confirmed nothing had changed.
I just have one of those feelings that we are missing something.
Hoplite808
Well-Known Member
- Jan 11, 2022
- 507
- Boat Info
- 1996 Sea Ray 270 Sundancer
- Engines
- Mercruiser 7.4 LX MPI EFI (Gen. V)
You seemed to be questioning my diagnostics and as I understood, you were alleging I was blindly throwing parts at it. I tried to explain as a response to that in my last post a condensed but detailed response to all the major repairs and diagnostics I’ve done so far. Where I’m at is all now is it runs but won’t accelerate past 2000 RPM’s, it’s not throwing any codes. Limp mode doesn’t exist in the ECU on this as it was built prior. Fuel system has clean fuel and appropriate pressure. @Scott215 if flow were an issue then pressure would drop. In order for pressure to be maintained there has to be sufficient flow. The compression test was done with the same gauge I’ve used on several other engine builds I’ve done successfully and gives me no indication of defect. The procedure I use is with the engine cold I remove all the spark plugs and then open the throttle all the way. Then connect the gauge one cylinder at a time and crank the engine over. I changed the alternator because the old one had the bearings fail and then it stopped charging. The IAC I changed out of caution as they are known to fail and I figured the price was comparatively minimal and I thought changing it would lead to less headache later.
@scoflaw I might have a lead on a reputable mechanic who will come “take a look” in a few weeks when he can squeeze me into his schedule. In the meantime I have to try and locate another shop that can correctly test the injectors and knows the parameters for the marine application. I suspect the shop I took them to did an improper test which gave me bad test data as they specialize in automotive rather than marine. The only marine injector shop here only does diesel.
Hoplite808
Well-Known Member
- Jan 11, 2022
- 507
- Boat Info
- 1996 Sea Ray 270 Sundancer
- Engines
- Mercruiser 7.4 LX MPI EFI (Gen. V)
@Scott215 I appreciate all the help and knowledge this forum is sharing with me. As the title of this thread says I am frustrated by this engine. For those who are befuddled by the lack of qualified mechanics and other services I mention. Hawaii has rated dead last by the NMMA out of all 50 states in boating for decades. Kansas has better boating industry infrastructure than Hawaii. For some reason Hawaii likes to keep the local government very liberal and even more incompetent.
You understood correct since you mentioned in your opening post just engine does not go over 2000 rpm,s and a list what you changed .
If i did not missed it its the first time yoy say now the alternator had worn bearings and stopped charging , as well i hear first time today your pushrods were bent and your manifolds cracked .
Nevermind and just to be crystal clear : when without gear you "drop the hammer" for a moment you say the engine revs up powerfully without any hesitation but in gear it is not able to push the boat past 2000 rpm - in any case unable to put it on plane . Correct ???
I asked about the alternator : can you exclude the voltage regulator was bad / overcharging and before you changed it it might have shot the ecu partially ?
If not and the engine is mechanically ~ healthy it has to be the injectors . You said you checked spark , spark advance etc.
Hoplite808
Well-Known Member
- Jan 11, 2022
- 507
- Boat Info
- 1996 Sea Ray 270 Sundancer
- Engines
- Mercruiser 7.4 LX MPI EFI (Gen. V)
Yes everything performs normally until about 2000 RPMs under load and then it just stops accelerating. Without the load (in neutral) it’ll rev all the way up to redline 4500 RPMs. It makes no noises currently to suggest an issue with mechanical parts in the block. It does not throw any codes or sound any alarms. Engine temp and oil pressure are within specs. The alternator wasn’t giving any issues to suggest overcharging. I think the previous owner let it sit unused too long and then when I went to use it the bearings just gave up. Also again the ECM is repeating code 12 which is it saying it’s self tested and working supposedly.
I had a couple of FAST setups then moved over to Motec and now Holley Dominator.
So on injectors I usually buy three sets of 8 and try to get them all from the same manuf batch. All 24 go to the calibration company and they test and select the 8 that have the closest volume and pattern - a matched set by test and calibration. There are usually a group of people I know that want the remaining 16 as I have the calibration sheets at no cost for them. For my applications all are Peak and Hold as I can get very large mass volume injectors to flow very small idle volumes and get an engine to idle quite respectably yet keep duty cycles less than 90 percent. Anyhow my method to get 8 matched injectors is not much more expensive even though I purchased quite a few.
I to really hope @Hoplite808 can get to the bottom of the issues he has to deal with. As news it appears he can rev the engine without load but when load is applied it hobbles at 2000 RPM - again, all the earmarks of injector flow problems. I suspect though his wallet isn't going to feel the same when this all done.
PlayDate
Well-Known Member
I have heard great things about the Holley Dominator EFI system. I haven't had the chance to work on one but Holley has acquired a lot of good companies along the way (MSD for one). They have found a way to stay relevant and make solid products.
My money is on the injectors as well.....or should I say I have 90% confidence. I'm glad he is looking for some local expertise to validate the injectors.
Ok , it revs up to 4500 but when you ( of course do it just for a split of a second ) in neutral slam the throttle full down , does it respond "aggressive" and "explosive" ?
I,m asking to know if you think the injectors give full fuel spray in this scenario .
This is a bravo drive ? Does your boat has a shift position sensor ?