1999 Supercharged 454 problems
 

Can anyone please help me? I have my boat into the repair shop and its getting expesive to try to diagnose the problem. What I have is a 1998 2330 Chaparral with a 7.4 Mercruiser and an addon 5lb boost procharger with inner cooler.
I noticed one that the thermostat has been removed. I put one in at 160 degree, but now am being told no thermostat is the way to go on this moter with the charger.
My big problem is the motor cuts out very badly at 3800 rpm. If I trim down and push water it cuts out even worse. Feels like there is much more rpm and power it wants to put out, but something is telling it to not go there. Any thoughts?

Is it getting fuel? Have you checked the plugs to see what they look like?

Becareful with the 7.4 under boost with problems. Don't want to burn a piston.

I would remove the thermostat, or go to a 140 unit. This will help to keep detonation away. Remember a 160 thermostat STARTS to open a 160, and isn't fully opened til about 180. Is the motor carbed or fuel injected?




Darrell.

It seems to be getting fuel although when its cutting out the pressure is bouncing from 10-50, but it seems to run rich. It's getting the plugs changed today and the compression is good at 150 on all cylinders. The plugs before where not the recommended plug so I put the in the NGK 5. It seems electronic based on how quickly it tries to recover after the cutouts.
I've checked vaccum lines but not the fuel filter etc. Have you ever heard of removing the thermostat in these motors with a charger to keep the charger cooler? Seems to me I want some heat in the motor? Also any idea what a the WOT rpm should be...46-4800?

So, you obviously have a fuel pressure gauge installed. If the pressure is erratic when it starts to cut out, I believe you have determined it is a fuel problem and not an ignition problem. Start with the easy stuff like changing the fuel filter, making sure you do not have a soft fuel line collapsing on you, etc. 4,600 is max RPM.

Exactly. Check all the easy stuff. Pump, filter, seperator, etc..

Pressure should not jump around.

Did you just add the ProCharger?

Or it has worked correctly and now is just experiencing this problem.

Like stated in the previous post, I would be looking at a fuel issue if the gauge is bouncing around to 10PSI.

Is the anti siphon valve out of the gas tank?

Procharger recommends no thermostat!

Thanks all! One more...
The mechanic just called and it doesn't appear to be pulling water in from the ports on the lower unit? I had it out two nights ago and it was moving water as I could see it coming out of the exhaust, plus I could see the water temp go up and down based on how I was running so I know it was getting water. could there be a blockage in the water movement to the engine causing it not to suck water? I'm sure the impeller was ok the other night.

You may have a water restriction problem, how high does the temp get while you are running? The water temp should not change that much. I am running without a t-stat and my oil temp creeps up when I run hard and comes right down but the water stays pretty constant.
Scott

The highest I've seen it so far is right around 170, but then as soon as I run full throttle (or as close to full as it will get now) it goes down to 120 in a matter of a few seconds.

At 3800 rpms you could be getting detonation which would cause this and possibly your fuel fluctuation. I run a t-stat without the guts and mine runes around 110-120.

kennyo, I think you are onto something here. My guts says its getting detonation. On an efi, how do I correct this? I ran it would thermostat at first and running at 110 has the same cutout at 3800. I wants to run faster I can tell and plenty of power it wants to make...it just can't.

Stock or aftermarket injectors? Same for fuel pump?

Believe the injectors would be stock, but the fuel pump seems to be upgraded. I unfortunately know nothing about this area. the fuel system runs though a red canister looking thing which appears to me aftermarket. My concern here is its not my dream boat and am at the point were I don't want to put much more into it so looking for the cost effective solution to get me through the next year or two till I upgrade.

A cost effective solution would be to take off the Procharger and put the motor back to stock. You could sell the Procharger and the boat would have better resale potential when you go to sell or trade it. Let's face it, a 2330 Chap is not a performance boat. And I'm not knocking Chaparral, I own one.

Be very careful with a blower on a non-Mag 454, you will cook a cast piston sooner or later unless your uber careful and have a perfetcly tuned setup.. I did it without a blower on my Chappy

I couldn't agree more on the fact it's not a peformance boat. I'd of never put a charger on it myself to begin with. If anyone has any other ideas, I'll keep playing around and paying my mechanic for a little longer then, the charger may just come off. Never running this boat without the charger...would I notice a big difference (its a 5lb boost), other than my hole shot?

If it ever ran right, you would notice a big difference removing it. Still, the boat will perform well in stock form.

:cool-smiley-011:
Presume it's an Alpha outdrive - sounds like the impeller, as the highr temps until you goose it - exactly what mine does every 5 yrs or so. As soon as new impeller, much more stable temp.
When did this start, or has it always done this cut out thing at 3800 rpm, I mean since you owned it?

No Alphas on 1998 7.4's. All Big Blocks in '98 came with Bravos.

I agree with removing the procharger and selling it. Expect to loose around 7mph off the top speed. You may not even know what top speed is though, since its doesn't run right. You'll need a smaller prop as well.

Thanks again all!
Yes it is the Alpha. I suppose the impeller should be replaced either way, but don't think that is what's causing the water not to pass thru as it worked fine the other night on the water.
I just picked this boat up this last winter so I'm not sure if it cut out last year. The previous owner said no and that it ran 5-10mph faster than I can get it up to. It was an ebay purchase though?
Feel like since I have the charger on it, I need to give it a chance and like the additional power, but running out of ideas and petty cash quick.

Typo...Bravo

Lose the T-stat. Does it cut out while hitting the trim button or all of the time? Check your connections on the fuel pump. Are you running the vacuum activated regulator to increase fuel pressure with boost? If it is runnibg out of fuel as others have suggested you will melt down the pistons for sure. Do you know if the ECM has been reprogramed? It could be detonation and the knock sensor is shutting it down. There is a chance also that the rev limiter is set up incorrectly in the ECM program. As the others say check the simple things first, clean fuel filters, check for flow, etc.
I am also ProCharged and do not run a stat. I make about 100 in running temp with little to no fluctuation. About 80 psi fuel pressure at wot and full boost. You may have a bad impeller with that kind of water fluctuation. The Aeromotive fuel system can put a huge load on your charging system causing the same issue cutting out if you have a weak alternator or battery.
A few things to look for.
Bob
A couple of things to start with.

It seems to be worse when the engine needs to work harder at those rpm (i.e. trimmed down). I'm not sure on the vacuum activated regulator though. Can the ECM be reprogrammed using standard Mercruiser programming or does the charger require something else. My shop is hesitant to work on this on since it's not stock. I'll check the batteries and filters first. Is your exhaust clean coming out of the pipes or do you see steam and maybe some whiter unburned fuel mixture at full throttle

Mine runs a little fat, I get some soot on the transom. It does get some steam at idle. If you are blowing white smoke at WOT I think you smoked a head gasket, that would explain all of it. It could have been caused by an overheat again go back to the impeler on the sea water pump. You should not see a flucuation in temp as you described.
Bob

Maybe I missed it, but are you running a fuel pressure guage? It would be interesting to know what fuel pressures you are running... I just removed a 7.4 mpi with a procharger running a stock ecm that ran very well for the last 100 hours....

I would guess you are using the stock "cool fuel" pump with a piggy back pump... looks like this:
Attachment 338845


It should have a bypass on the stock fuel pump to replace the stock rugulator (this is usually red also and is tucked way down under on the stock fuel pump) and then you should have an aftermarket boost referenced regualtor (also probably red)

If you check your base pressure, probably 40-45 or so and then see if it begins to climb as you loose vacuum and go into boost, you will know if it is working correctly.

I just put my charger system on a 454mag and had the ecm programmed and it runs like total ****!!! turns out the program is just plain too much fuel and it won't hardly plane out, and just bogs out from over rich condition around 3000 rpm.

You definately don't want to go lean on that engine, but you might be getting to much fuel when the regulator see's boost
and raises the pressure... Does it take a second to "clean up" when you bring the throttle back ?

Another thing is if you are runnig a thermo with no bypass for the ehaust, they will get nice and hot until the stat opens and that could be the steam you are seeing ????

Try this guy @ www.mefituning.com

If the problem is electronical the issue I would agree. If it is a mechanical problem that would nedd to be addressed first.

lilwigs, I don't mean to hurt your feelings but youand your mechanic are obviously in over your head. There are literally hundreds of posts on here to read that will cover all your ???. Either take it to a MARINE mechanic with blower experience or get ready to learn many expensive lessons.
The search feature will answer almost all your ?? because all of us running a procharger have asked or found out the hard way before!

Good luck Brother, hope you get it fixed,Ken.

P.S. I've had a fuel pump work at cruise and fall off at WOT. It good be simple as that. I would recommend taking it off also. You won't regret it.

Thanks kennyo! You are correct about me being in over my head. My problem is I'm in Nebraska and can not find a shop willing or able to workon my setup. They did find two fouled plugs and replace the impeller, but that was all the marine store could do for me.
I hear the general concensus and think taking it off is the way to go. Thanks for all of your help and wish me luck...giving it another month, then there may be one heck of a steal on a 99 Chappy on ebay for the right person.
Thanks all!

Don't give up, but DO NOT run the boat hard untill its figured out.

If the fuel pressure is jumping around that is a main problem. Make sure your fuel pressure regulator is good. Make sure your fuel pump is good. Make sure your filter is clean.

Are you running this boat on 93 pump gas? I'm sure it needs it.

Get in there and get your hands dirty.

[QUOTE=lilwigs;2541741] My problem is I'm in Nebraska and can not find a shop willing or able to workon my setup. giving it another month, then there may be one heck of a steal on a 99 Chappy on ebay for the right person.

Wigs before you put it on ebay let us know if your gonna move on to another boat and we'll come get it :cool-smiley-011::D good luck

[QUOTE=RunninHotRacing158;2541786]Where are you at in Nebraska?

I'm running 91 octane pump fuel. I'm located in Lincoln, NE unfortunately. I pick it up from the shop today and afraid it'll be another few weeks till I can get this in someplace else but not sure where. I'm pretty mechanical, but never really had to troubleshoot this type of deal. When the fuel pressure guage jumps I'm not sure if it's the "cause" or effect of it missing at those rpms. I did find out the impeller did need replacing and they removed a piece of plastic that was blocking my upflow of water. It was still pumping though? I did have them replace the old fouled plugs with the NGK 5 or 6. Is advancing the timing something anyone has done with the computer. I was under the assumption the taking the tstat out was to trick the motor into dumping more gas and the charger wouldn't need any additional setting changed on the motor.

For anyone not tired of my questions I think I have my problem narrowed down, but could use some final advise. With new plugs and impeller replaced it is running better. This was not my issue, but in running it for an hour last night I did notice my fuel pressure when I turned on the key was right at 40, then under normal running it would run 30-35. Under full boost at around 4000 rpm I can see the pressure fall to 20-25 and then it starts to cutout and surge as the pressure goes from 20 - 40. Just out of curiosity, I put a kink in the vaccum line to the regulator and to my surprise no performance difference. So that said I'm almost positive its in the fuel supply somewhere. Unfortunately I know nothing on this topic. I'm assuming the pump is fine since it hits 40 on turn key, but somewhere in the process I am unable to keep pressure. Looking at changing the seperator and fuel filter, but is my next step a new regulator? How can I test without just changing piece by piece? Thanks in advance to anyone who can help!!

Just a couple things. First NGK 5/6's are HOT plugs. Be sure this is what you should be running. Call procharger and ask. Second, the fuel pressure should not be falling off. I believe this is where your problem lies. I personally wouldn't run the boat with it doing that.
That is the PERFECT way to damage a piston. You are on the right track, change out all of the fuel filters, and water seperators. And, be sure there are no blockages in the lines. After this is done, then, start to look at the regulator and pump.


Darrell.

Just my. 02. You have a fuel problem no doubt about it. There is a difference between a fuel pump and/or system making pressure at idle and it not being able to keep up with demand at higher rpms. My guess is the entire fuel system is inadequate or improper and that the prior owner couldn't make it work.

I will second all of those that have said that you are going to hurt the motor running it that way. I learned the hard way years ago. I would never again guess at the problem. You really need to get someone who knows what they are doing or forget the procharger. I hope you don't learn an expensive lesson.

Make sure your fuel tank vent is not plugged of restricted. When you fill will fuel can you do it on full flow without the gas station pump nozzle clicking off?

I agree with the fuel regulator on an aeromotive fuel system. The vacuum regulated fuel regulator is to increase pressure with boost. I think you have a bad diaghram in the regulator. It is kind of common.
Bob