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
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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.
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.
Thats a good approach and i do not want to argue but let me again quote your own initial posting :
Assuming you have basic tools like a 10$ volt meter and a compression tester changing heads , the alternator and the IAC for an engine that idles but just struggles to rev above 2000 in gear is about as useful s changing the toilet seat for your issue.
With a bit more diagnostic ( assuming you can verify its not overheating , not in limp mode ) changing tstat housing , impeller and housing is about the same.
Hard to comment you changed the entire outdrive just for this ... amazing.
I,m asking just to learn what the hell are you doing ??
I,m afraid you already have a frankenstein setup since IT IS a senseless shooting in the dark up to know .
If you want to go boating i would recommend to diagnose usefully and in future aim before taking a shot or we can go back to the carb conversion on an MPI ( since you ordered 8 injectors i guess its indeed a multiport injection , not a singleport EFI )
Sheesh John - It sounds like you want him to move over to carbs?
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 $1000 - more like 3 or 4K. Can a new marine distributor curved for that engine even be obtained these days for carburetors? It seems the poor guy can't get his head around the fuel injectors being the most probable issue at this point. More concerning is if the used Ebay injectors he acquired and tried to use were Peak and Hold, he might have really damaged the ECM. He did say that his resistance measurements were not in spec on them which is rare on an injector.
More concerning is if the used Ebay injectors he acquired and tried to use were Peak and Hold, he might have really damaged the ECM. He did say that his resistance measurements were not in spec on them which is rare on an injector.
@Hoplite808
You wrote that you have issues with an engine failing to acclerate the boat past 2000rpm,s - now you say it has beyond that issue problems everywhere . Cracked manifolds , shot gimbal , worn outdrive , bent push rods , scorched impeller pump etc.
Are we talking about an engine struggling to rev past 2000 ( where changing the alternator as trouble shooting is silly nonsens ) or are we talking about virtually anything worn or shot ?
Help yourself to get help here and clarify as good as you can what exactly you did , what parts you changed for what reason and where you got these parts .
Regarding compression : imho 120-125 might open room for a discussion if the engine misses 200-300rpm on top end but no if it struggles to rev past 2000 . I agree the compression is ok , the engine maybe a bit tired but acceptable . And it depends on the gauge and your procedure ( wot during testing ?)
Regarding IAC : iac might be an issue during starting and idle , it has zero effect at 2000rpm and above .
Regarding your 10$ voltmeter ? It shows if your alternator is charging or not Why did you replaced it?
You seemed to be questioning my diagnostics and as I understood, you were alleging I was blindly throwing parts at it.
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.
I had a couple of FAST setups then moved over to Motec and now Holley Dominator.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.
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.
Without the load (in neutral) it’ll rev all the way up to redline 4500 RPMs.