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#572643 - 08/04/19 02:24 PM Help - Acceleration Issues  
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athiker Offline
Admiral
athiker  Offline
Admiral

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Posts: 3,902
Lake Norman, NC
I have the boat in my signature, engine still starts great (after last year's repairs), idles fine and can cruise fine. The problem is any time I want to accelerate quickly it bogs down so I can't pull up skiers and wakeboarders. This happens even if not trying to pull someone up with only 2 people in the boat. If I accelerate slowly I can get on plane and run great at 40 mph +.

I have changed the fuel water separater/filter and the prop (it was getting old) with a new hub kit to no avail.

Fuel pump? Anything easier anyone would suggest checking? Thanks.

P.S. I haven't been around much lately as this has been kind of a lost boating summer. Knee surgery and other things have kept us off the water for the most part, but I'd love to make up some lost time the 2nd half of the summer.


2000 Cobalt 206 5.7L EFI Alpha 1
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#572652 - 08/06/19 11:07 AM Re: Help - Acceleration Issues [Re: athiker]  
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tpenfield Offline
Admiral
tpenfield  Offline
Admiral

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Cape Cod, MA
You could check the pressure at the fuel rail to see if it is within spec. Did this come on suddenly or gradually? If gradually, I'd go for a heavy dose of injector cleaner with a small amount of fuel. If suddenly, I'd check the fuel pressure at the fuel rail. There should be a schrader valve somewhere . . . idn


Regards, Ted

Formula 330SS

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#572656 - 08/06/19 12:29 PM Re: Help - Acceleration Issues [Re: athiker]  
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Frantically Relaxing Offline
Admiral
Frantically Relaxing  Offline
Admiral

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I'm going with injectors. Injectors will squirt pee-streams when dirty and still flow near their max- At high rpm the engine can atomize the raw fuel enough to use it, and make reasonable power, but at low RPM a pee-stream of fuel won't atomize; since liquid gasoline won't ignite the mixture that will ignite is extremely lean...

And guess what can clog up injectors, that every boater religiously uses...? ('cept me wink )



Stabil...

I have a bottle I found on board the SkipperLiner, I keep it around just to show people. The older it gets, the more it turns to glass. Pretty sure it's also the source of the carb issues in the Party Cruiser's outboard, it's the only possible reason for the green 'glass' buildup in the carb bowls that breaks loose and clogs the friggin jets...

Sorry for the rant-- I know the stuff works but it comes at a price. And Seafoam won't break it down.





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#572657 - 08/06/19 05:29 PM Re: Help - Acceleration Issues [Re: athiker]  
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Jack T Offline
Admiral
Jack T  Offline
Admiral

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Southern California
"Pretty sure it's also the source of the carb issues in the Party Cruiser's outboard, it's the only possible reason for the green 'glass' buildup in the carb bowls that breaks loose and clogs the friggin jets."

The bottles I have are stamped with a "use by" date. Perhaps your one bottle was produced before the use by date was standard.


Have a great day of boating
2012 Monterey 224 FS,
300 HP Volvo Penta with catalytic converters

#572658 - 08/06/19 10:21 PM Re: Help - Acceleration Issues [Re: athiker]  
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athiker Offline
Admiral
athiker  Offline
Admiral

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Lake Norman, NC
Thanks, I would say it came on pretty suddenly late last season. We have not used the boat a ton the last few summers so it could be some not so fresh fuel. I've always filled up with non-ethanal fuel, but haven't been too good with Stabil over the winters.

This engine only has a throttle body, its not an MPI, so really I think the fuel drops into basically a carb body from one spot, no multi-port fuel rail on each side of the engine. I will get some carb cleaner and spray around the intake area. I guess I could try a fuel additive as well.

I'll need to do some looking to see if and where I can test the fuel pressure. I have never done this nor do I know how. Thanks again for the suggestions.


2000 Cobalt 206 5.7L EFI Alpha 1
#572659 - 08/06/19 10:39 PM Re: Help - Acceleration Issues [Re: athiker]  
Joined: Dec 2003
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athiker Offline
Admiral
athiker  Offline
Admiral

Joined: Dec 2003
Posts: 3,902
Lake Norman, NC
Any thoughts on it being the fuel pressure regulator? I assume it has one?


2000 Cobalt 206 5.7L EFI Alpha 1
#572660 - 08/06/19 11:12 PM Re: Help - Acceleration Issues [Re: athiker]  
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Frantically Relaxing Offline
Admiral
Frantically Relaxing  Offline
Admiral

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Posts: 11,857
I was thinking you had multi-port injection-- with TB injection you can just watch the injector's spray pattern yourself as the unjectors are right on top of the TB, and spray right down the throat. Even at idle the injectors spray a fine mist you can see, it's surprising how much fuel DOES spray at idle. (With a carb you never see idle spray as that happens under the butterfly valves)

Clean injectors will spray a nice, uninterrupted 360° cone-shape of fuel. The spray will be intermittent at times which is normal, but always 'full circle'. If the circle is broken or the injector drips, it needs cleaning...

Open the throttle and you should instantly see lots more fuel spray. If it doesn't bother you to do this on the water, you can watch the flow under real conditions. If the spray itself looks good, does the amount fluctuate? At WOT, if you're starving for fuel you can probably see it happen...

And yes it could be the pressure regulator, should be a schrader-type valve somewhere to check pressure, they can get weak...

Found this video showing the injector spray, shows idling and getting on it a bit--

https://youtu.be/5A4a5OOGqPo


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#572661 - 08/07/19 12:47 PM Re: Help - Acceleration Issues [Re: athiker]  
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Jack T Offline
Admiral
Jack T  Offline
Admiral

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Southern California
Good info FR. Sounds like a good troubleshooting process.

ATH. Do you know how much fuel is currently in the tank? Maybe removing a good sum (half the tank or all) and adding new fuel would help diagnose. Or, I believe someone suggested using an auxiliary tank of some kind and hook it up to the intake of the fuel pump. Gravity feed would be helpful. Then run the new fuel though the system.. If the engine runs fine under the fault circumstances, then you might be able to say that the problem is not the engine fuel system but either bad fuel or a tiny air leak in the fuel tank or line.

I am not sure if there is a way to get a sample of fuel checked, but it might be worth finding out.


Have a great day of boating
2012 Monterey 224 FS,
300 HP Volvo Penta with catalytic converters

#572666 - 08/08/19 12:27 PM Re: Help - Acceleration Issues [Re: athiker]  
Joined: Dec 2003
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athiker Offline
Admiral
athiker  Offline
Admiral

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Posts: 3,902
Lake Norman, NC
Thanks so much for the info. I watched the video and can definitely check that out this weekend.

Re: fuel tank I have about half a tank, but its a 50 gallon tank. Since it starts and runs okay on plane, it just bogs down badly getting on plane, I agree we should take a nice long run this weekend and use up some fuel and refill with fresh stuff to help remove that as a problem source.

I will also look for the schrader valve to see if I can test it. If it has one it looks like I get to buy a a new tool. laugh I see they sell kits to let you cut and tap into the fuel line as well if it comes to that.

BTW, what you you expect to be "normal" psi? And should it be the same static as when the engine is running? I see a bunch of car videos that seem to be mid-40s but I think the TBI is around 15?

How does this procedure look to test? https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

To clean? https://itstillruns.com/clean-chevy-tbi-fuel-injuctor-7745248.html

Thanks again.


2000 Cobalt 206 5.7L EFI Alpha 1
#572667 - 08/08/19 03:10 PM Re: Help - Acceleration Issues [Re: athiker]  
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Jack T Offline
Admiral
Jack T  Offline
Admiral

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Southern California
"I see they sell kits to let you cut and tap into the fuel line as well if it comes to that."

Since I don't know about this tuff, if I were considering this, I would definitely find out if it is marine approved.


Have a great day of boating
2012 Monterey 224 FS,
300 HP Volvo Penta with catalytic converters

#572668 - 08/08/19 03:12 PM Re: Help - Acceleration Issues [Re: Jack T]  
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athiker Offline
Admiral
athiker  Offline
Admiral

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Lake Norman, NC
Good point, thanks....I would like to keep all explosions confined to INSIDE the engine.


2000 Cobalt 206 5.7L EFI Alpha 1
#572669 - 08/08/19 06:30 PM Re: Help - Acceleration Issues [Re: athiker]  
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Frantically Relaxing Offline
Admiral
Frantically Relaxing  Offline
Admiral

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I used to like the internet, but these days it's about worthless for finding actual information. I've spent 20 minutes trying to help out, googling every variation of "what is the fuel pressure range of a 2000 GM TBI 5.7 marine engine", and *almost* ALL that comes up is: a bunch of ads for everything injection, and a multitude of forum posts like this one with someone asking similar questions resulting in a lot of opinions but no firm answers.

But I did find this sentence at the top of This web page, which is copyrighted 2006-2018, so I suspect it's reasonably accurate as it goes into certain 1990's trucks...

Quote
The fuel pressure regulator is set for approximately 12 psi (30 psi on '94 & '95 BBC trucks). With a service range of 9 to 13 psi being considered good.


--the page is a lesson on how to set up TBI injection for high performance engines, kind of interesting reading...




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#572671 - 08/08/19 10:24 PM Re: Help - Acceleration Issues [Re: athiker]  
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kenhdog Online content
Admiral
kenhdog  Online Content
Admiral

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Oxnard, CA
My SELOC for Mercruiser shows for 2001 and 2002 5.7 EFI the fuel pressure is 30psi at 1800 RPM.

The book has some Fuel System Troubleshooting guides over a few pages, if you want me to scan them.


2002 Rinker 212 Captiva
Merc 5.7 EFI Alpha
Trail-Rite Trailer
1999 GMC 'Burb
#572674 - 08/09/19 12:00 PM Re: Help - Acceleration Issues [Re: kenhdog]  
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athiker Offline
Admiral
athiker  Offline
Admiral

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Lake Norman, NC
Thanks guys. I will read over that website this weekend FR and thanks Ken for the scanned pages. They look like they will help troubleshoot. I see the same 30 psi at 1800 rpms that you reference. Kind of odd vs the mid teens I've seen for cars and that FR referenced.

Good thing is from reading through the pages it looks I should expect to find a valve to test the fuel pressure.

Thanks again


2000 Cobalt 206 5.7L EFI Alpha 1
#572677 - 08/09/19 02:11 PM Re: Help - Acceleration Issues [Re: Frantically Relaxing]  
Joined: Jun 2005
Posts: 3,528
kenhdog Online content
Admiral
kenhdog  Online Content
Admiral

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Oxnard, CA
Originally Posted by Frantically Relaxing
.... "what is the fuel pressure range of a 2000 GM TBI 5.7 marine engine", and *almost* ALL that comes up is: a bunch of ads for everything injection, and a multitude of forum posts like this one with someone asking similar questions resulting in a lot of opinions but no firm answers.


Not much better results, but you have to use the Mercruiser lingo. rolleyes
"5.7 EFI" = TBI
"5.7 MPI" = Fuel Injected/Port Injection.


2002 Rinker 212 Captiva
Merc 5.7 EFI Alpha
Trail-Rite Trailer
1999 GMC 'Burb
#572688 - 08/11/19 08:10 PM Re: Help - Acceleration Issues [Re: athiker]  
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Jack T Offline
Admiral
Jack T  Offline
Admiral

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Posts: 3,962
Southern California
Do engines equipped with TB have oxygen sensors in the exhaust? Could that be part of the original problem?


Have a great day of boating
2012 Monterey 224 FS,
300 HP Volvo Penta with catalytic converters

#572690 - 08/12/19 01:28 AM Re: Help - Acceleration Issues [Re: athiker]  
Joined: Feb 2003
Posts: 11,857
Frantically Relaxing Offline
Admiral
Frantically Relaxing  Offline
Admiral

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Posts: 11,857
I was thinking, not on a boat, but thought I'd check some photos...

seems yes on a boat, 4 of 'em stickin' out like sore thumbs in the Regal...

[Linked Image]


===============
whether or not they could be contributing to the issue... idn
-could be, but...?


[Linked Image]
#572710 - 08/14/19 12:09 PM Re: Help - Acceleration Issues [Re: athiker]  
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athiker Offline
Admiral
athiker  Offline
Admiral

Joined: Dec 2003
Posts: 3,902
Lake Norman, NC
Unfortunately I didn't make it to the boat this weekend or this week yet...will post when I find out anything new. Thanks for the continuing suggestions.


2000 Cobalt 206 5.7L EFI Alpha 1
#572711 - 08/14/19 08:10 PM Re: Help - Acceleration Issues [Re: athiker]  
Joined: Jul 2003
Posts: 6,645
Dave R Offline
Admiral
Dave R  Offline
Admiral

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Posts: 6,645
Raymond NH
Check your water shutters (exhaust flappers) I bet you have one partially blocking the exhaust.


"Mischief Managed II"
1992 Tollycraft 44 Cockpit Motor Yacht
Twin CAT 3208TA inboards
#572713 - 08/15/19 08:55 PM Re: Help - Acceleration Issues [Re: athiker]  
Joined: Dec 2003
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athiker Offline
Admiral
athiker  Offline
Admiral

Joined: Dec 2003
Posts: 3,902
Lake Norman, NC
Thanks Dave R - yikes! Just watched this after reading your comment.

Mercruiser Alpha One Gen Two Exhaust Flappers

Hoping to get time this weekend to check some things.


2000 Cobalt 206 5.7L EFI Alpha 1
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