Logo
Page 2 of 3 FirstFirst 123 LastLast
Results 31 to 60 of 77
  1. #31

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Did something I shoulda done at first: check the Anti-Siphon Valve (ASV). Put a quart jar in the bilge, pulled the fuel line off the tee and stuck in the jar, which proceeded to fill up. Hardly think 6 ft of 3/8 fuel line could have a quart of gas in it. Re-attached the fuel line, pulled the back seat and removed the ASV. The ball valve was jammed part way open with a thin but stiff wire. So it couldnít close when it was suppose to, or open all the way either. Your guess is as good as mine how it got there. Yanked the wire, reinstalled the valve, started the engine and let it warm up for a test run. As soon as I tried to throttle up, the engine died and wouldnít restart. So does this mean the ASV is shot, or that the mechanical fuel pump canít generate enough suction to pull the valve open? ASV pics below. Pretty sure its original and 23 years old just like the boat. Anybody know what the screw on top is? Any way to bench test the valve? Itís an inexpensive part, so Iíll go ahead and replace it. Looking forward to yr advice.

    Click image for larger version. 

Name:	ASV1.jpg 
Views:	6 
Size:	29.5 KB 
ID:	16410

    Click image for larger version. 

Name:	ASV2.jpg 
Views:	9 
Size:	33.4 KB 
ID:	16411

  2. #32

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Oh. The fuel tank is stainless steel if that makes any difference.

  3. #33
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,758

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    you could use a 90-degree hose barb adapter for "temporary" testing purposes....

    the screw is likely just to secure the spring and the check ball....

    the ASV works similar to a check valve - it only passes fuel when enough suction is applied to the outlet....you be hard pressed to find the spec on any given valve even though they are made with different 'cracking pressures'.

    given the aftermarket high pressure pump, I'd think its pretty easy to 'T' your pressure gauge into that hose....and not knowing if the pressure to the TBI is adequate makes the rest a guessing game. If there are any ID marks on the high pressure pump, that could help resolving the issue too...

  4. #34
    Join Date
    Nov 2005
    Location
    Mt. Zion, Illinois,
    Posts
    491

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Looks like lots of corrosion and junk in the ASV. I'd take MakoMark's advice and install a temporary 90* hose barb adapter and try your lower pressure pump test again. If you're low pressure is good and steady with the ASV removed then it's narrowed down a little.

    The problem could be the ASV only. You might be able to use carb cleaner or let the ASV soak in SeaFoam for a day or two. Then, work the ball valve back and forth rinsing with cleaner until the ball moves freely with very little resistance. If you can get the ASV into good shape, reinstall it and see if the pressure looks the same as with the regular 90*. If the pressure stays the same take it for a load test and see where you are.

    If the pressure drops with the cleaned ASV then your next step is to either assume the low pressure fuel pump is bad or the ASV is just sticking. At that point you'll need to replace parts to see which one is the problem.

    KJ

  5. #35
    Join Date
    Jun 2008
    Location
    Island Heights, NJ,
    Posts
    2,566

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Stainless should only be used as a material for gas tanks, if it never gets wet. Otherwise use Marine-grade aluminum, type 5052, 5083 or 5086.

    Also ASF's are so cheap, readily available and critical for boat safety, that cleaning/rehabbing one is only something I would do if I was at sea and could not get towed.

    http://newboatbuilders.com/docs/PY_JAN09_51-54_FUEL_TANKS.pdf



    Capt Bob
    1969 23ft ChrisCraft Lancer
    Merc 5.7L 260HP/ Volvo 280
    1972 22ft Bristol
    Honda 7.5HP 4 stroke Long shaft

  6. #36

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    VICTORY! No more surging and WOT is 4450! Per makomark, installed an open test elbow. BINGO! I think there may still be minor fuel pressure issues, but I have all the gear to test that and wiil do so. But top speed is still only 37mph according to the GPS app on my phone. Maybe tachometer is wack? Anyway, very happy to have solved this with all yr help. THANKS!

  7. #37

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Glad to hear it was something simple. On top speed yes would verify the tach but also what prop pitch is on it? Most ski boats are set up for low end pull vs top speed.

  8. #38
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,758

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    2X on the simple....

    Would be a good time to get some baseline data to add to your log book in case it happens next time.....and don't forget to replace the 'test elbow'....

  9. #39

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Prop is factory OE: 13x13 Cup OJ Legend. On the 3 other tournament tow boats I've owned, direct-drive 1:1 systems with factory props usually produce speeds that correspond to 1mph per 100 rpm. If the current boat follows that rule, top end should be 43-44 mph. Will check with the boat builder to see what they say.

  10. #40

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Uh.. what's a logbook? I'm not that buttoned up. New anti-siphon valve arrives Tuesday.

  11. #41

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    According to this Waterski Mag test of my boat when it was new, top speed was 46.7. Looks like I still have some work to do.

    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	Screen Shot 2017-09-02 at 12.22.45 PM.jpg 
Views:	68 
Size:	25.5 KB 
ID:	16429  

  12. #42
    Join Date
    Jun 2008
    Location
    Island Heights, NJ,
    Posts
    2,566

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    What max wot range is listed on the flame arrestor decal? Also are you SURE that the factory prop is the one that is actually on the boat?
    Capt Bob
    1969 23ft ChrisCraft Lancer
    Merc 5.7L 260HP/ Volvo 280
    1972 22ft Bristol
    Honda 7.5HP 4 stroke Long shaft

  13. #43

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Flame arrestor decal states WOT is 4400-4800rpm. I've inspected the prop markings: 13x13 LH cup; 1-1/8" OJ Legend. Per the image posted above; if it's not the original prop, it's the same spec.

  14. #44
    Join Date
    Nov 2005
    Location
    Mt. Zion, Illinois,
    Posts
    491

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Quote Originally Posted by pwskicat View Post
    According to this Waterski Mag test of my boat when it was new, top speed was 46.7. Looks like I still have some work to do.
    Are you sure? The image you posted is pretty low quality and gets grainy when I enlarge it. But, if I'm reading that chart correctly, the highest value on the Y-axis is 40MPH and the dot on the chart looks to be at 36.7MPH. Is that correct? If so, it sounds like you're right on spec.

    KJ

  15. #45

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Sorry for the lo-res screen shot. The dot on the chart is the 0-36mph time. Kinda like 0-60 for cars. Here are the stats from the boat test under the "ACCELERATION/TOP SPEED" header on the chart:

    To 36 mph, 7.04 seconds, 237 ft.
    To 40 mph, 9.50 seconds, 375 ft.
    Top Speed: 46.7 mph

    I have a few more tests to run on the fuel system to make sure fuel pump pressures are OK and that everything is up to spec once I get the new anti-siphon valve in. I also have a test tach coming to see if my boat tach is reading right or is way off. Finally, if the prop was ever repaired, it might not be pushing all the water it's supposed to. My buddy in California has the same boat, and he just got a GPS speedo for it. He'll be doing some speed runs this weekend, including WOT. He'll tell me what his speeds/tach readings are, and that will hopefully give me a baseline to work from.

  16. #46

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    The electric fuel pump that was used to replace the Vapor Separator Tank (VST) is a Walbro GSL395. It’s an automotive part and I don’t think it can replicate the function of the VST fuel pump. Here’s why: I did the high-pressure fuel pump test per the service manual. Key on, the electric pump runs for two seconds and the test gauge indicates 30psi, which is right on spec. The pump shuts off, and the pressure is supposed to hold, but in my boat, the gauge immediately drops to zero. Then I did the fuel pressure regulator leak down test, plumbing a fuel shut off into the fuel return line and applying 12V to the pump. The gauge shot up to 60psi, which is right on spec, and held, which is exactly what it’s supposed to do. So, does the VST have some kind of check valve to hold the initial pressure from the 2-sec pump operation? Is that functionality missing from the Walbro pump? If so, I’m screwed, because there is no part number other than the VST, which, while I said I found one earlier, is actually no longer available. The pump that goes in the VST is available for $725, but you gotta have the rest of the assembly for it to work. Lastly, I took the boat out today, and with my buddy driving, saw that the test gauge on the high-pressure pump held 30psi steady at all throttle settings, and the gauge on the mechanical pump rattled between 4-5psi at anything above 2000rpm. Took the test gauges off, and ran the boat. The surging is still there, but not as pronounced, and the boat still only tops out around 36mph, and the tach goes wonky when I try WOT, so I’m not even sure how high the boat is revving. None of my buddies or I ski faster than 30, and I drove it around the lake a few times at 30 and it was OK. Not perfect, but OK. I guess I could replace the electric fuel pump with a new one and see if that improves anything. That would only be $135. Or convert the TBI to carburetor. That would cost probably $1k. That said, there’s a new anti-siphon valve on the fuel tank, a new Tygon sight tube running from the mechanical fuel pump to the flame arrestor, USCG Type 1A fuel line throughout and new stainless-steel hose clamps at all unions.

    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	Screen Shot 2017-09-10 at 4.55.06 PM.jpg 
Views:	45 
Size:	21.3 KB 
ID:	16469  

  17. #47
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,758

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    I don't think the Walbro pump provides enough fuel to satisfy the engine at elevated RPM....so I'd suspect that's a big contributor to the surge....

  18. #48

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Thanks, mako. I'll contact Walbro and.see what they say.

  19. #49
    Join Date
    Nov 2005
    Location
    Mt. Zion, Illinois,
    Posts
    491

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Quote Originally Posted by makomark View Post
    I don't think the Walbro pump provides enough fuel to satisfy the engine at elevated RPM....so I'd suspect that's a big contributor to the surge....
    That spec sheet shows 130 LPH which converts to 34 gallons per hour max flow rate on the Walbro.

    According to these numbers on boat fuel economy, that flow rate should satisfy just about any Mercruiser engine except for the thirsty 8.1L and 8.2L. I know your pressure readings come out right, but is it possible that you're maintaining pressure but not sufficient flow? Maybe there's a restriction in your pressure regulator that is limiting flow to the engine but is maintaining correct pressure?

    http://www.boat-fuel-economy.com/mer...ion-us-gallons

  20. #50

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Kevinj: Good info about the Walbro fuel capacity. Good question about fuel restriction. How do I test for/remedy it? Thank u.

    Found out that I can get an aftermarket check valve to hold pressure in the system after the initial pressure up created when the ignition is turned on. Keeping the system pressurized would show if the injectors are leaking. The part runs anywhere from $32 to $50. Does this sound like a wise investment?

  21. #51
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,758

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Quote Originally Posted by kevinj View Post
    That spec sheet shows 130 LPH which converts to 34 gallons per hour max flow rate on the Walbro.
    not at 30 PSI......

  22. #52
    Join Date
    Jun 2008
    Location
    Island Heights, NJ,
    Posts
    2,566

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Nowhere does it say the WALBRO is USCG /NEMA certified. QS9000 is an automotive certification.
    Why not just replace the mechanical with the same marine electric used on other 5.7's ( with appropriate oil pressure cutoff of course).
    Doubt that your current system's inability to hold pressure when not running has anything to do with not enough fuel at speed. Your problem could be as simple as a vacuum leak on the system's suction side.
    Last edited by sandkicker; 09-11-2017 at 05:39 PM.
    Capt Bob
    1969 23ft ChrisCraft Lancer
    Merc 5.7L 260HP/ Volvo 280
    1972 22ft Bristol
    Honda 7.5HP 4 stroke Long shaft

  23. #53

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    @makomark So quantity of fuel delivery decreases as psi increases? Do you know of a formula or chart that shows what the fuel delivery rate for a 130lph pump is at 30psi? Many thanks for yr help.

  24. #54

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    I've tested for vacuum leak and found none. The marine pump for this engine works only with the no-longer-available Vapor Separator Tank (VST), which my exhaustive web search reveals is indeed no longer available, new or used. I know that the Walbro pump, which a previous owner installed when they took out the VST, is an auto part, is not the right part. So I'm stuck with devising a workaround with whatever the market can provide.

  25. #55

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Given the tach is wonky I would recommend disconnecting it at the negative post on the coil (grey wire) and take a trial run. I understand you've been focusing on fuel, which makes sense, but a bad tach can short the ignition system.

  26. #56

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Apologies may have given you bad info on the tach wire color, on the EFI coil i believe it may be a white wire in the efi harness. Long story short the easiest way to take the tach out of the equation is to disconnect the grey wire at the sense terminal on the back of the tach.

  27. #57
    Join Date
    Jun 2008
    Location
    Island Heights, NJ,
    Posts
    2,566

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    using an automotive part in the fuel system...
    1) Illegal
    2) Dangerous
    3) Insurance won't pay if there is a fire problem...
    Capt Bob
    1969 23ft ChrisCraft Lancer
    Merc 5.7L 260HP/ Volvo 280
    1972 22ft Bristol
    Honda 7.5HP 4 stroke Long shaft

  28. #58

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    Today I installed a Walbro GSL393, which has a flow rate of 38gph at 30psi, as opposed to the old GSL395, with a flow rate of 0gph at 30psi. Also put in a 10-micron fuel filter/separator with a flow rate of 90gph, which is required as a prefilter. Took the boat out and it ran to 4400 WOT, but gradually dropped off RPM to below 4000. After cruising at 3000 for awhile, engine began coughing and stalled. I sat in the lake for 5 minutes, and got it started, took if up to 2100, and it stalled again. After getting it started one more time, I idled back to the dock. Here is a quote from post #30 by Dieter:
    Looks to me that the low pressure pump is inadequate, would expect a constant output pressure. This maybe a result of the fact this pump is discharging directly into the suction of the high pressure pump with no accumulation. The set up originally on there had in effect a reservoir the low pressure pump pushed into, the drop to zero you see now may just be the cycling of the diaphragm in the pump. I would think with no reservoir between the two pumps this would lead to a fuel starvation and surging.

    The only "reservoir" in the current set up is the filter/water separator, which is supplied by the mechanical pump on the engine. Is the new high-pressure pump sucking all the fuel out of the filter/separator and the mechanical pump can't keep up?

    Ski season is over and I'm at a loss. Will any remedy work without the damned unobtainable Vapor Separator Tank? Should I remove the mechanical fuel pump and try using the electric pump alone? Remove the mechanical pump and install the low-pressure electric pump I just removed in its place? Should I buy another high-pressure pump and substitute it for the mechanical pump? Should I put a carburetor on the damned thing? Your guess is as good as mine.

  29. #59

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    NOTE: The fuel return from the TBI is dumping into the filter/separator. That is sending a huge amount of fuel back to that "reservoir." How can the system be starving?

  30. #60
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,758

    Default Re: Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed

    without some pressure measurements, its hard to say what's happening where.....

    does the new pump 'require' the low pressure pump? It may not, in which case if you locate it lower, the better it will be as far as heat collection goes.

Page 2 of 3 FirstFirst 123 LastLast

Similar Threads

  1. Inboard '95 Mercruiser GM 350 EFI Magnum Skier limited top speed
    By pwskicat in forum Other Gas Inboard Mfgs IO and Sterndrive Questions
    Replies: 1
    Last Post: 08-02-2017, 06:10 PM
  2. Mercruiser 4.3 262 Magnum EFI Gen +
    By 650 in forum Mercruiser Sterndrive Forum
    Replies: 0
    Last Post: 06-14-2015, 10:42 AM
  3. Mercruiser 350 Magnum Inboard Help
    By 98sanger in forum Mercruiser Sterndrive Archive
    Replies: 2
    Last Post: 05-26-2009, 04:45 PM
  4. Replies: 21
    Last Post: 08-28-2008, 08:00 PM
  5. 1997 alpha 1 carbureted Chevy 2 bbl speed limited
    By xz95xj in forum Mercruiser Sterndrive Archive
    Replies: 5
    Last Post: 07-09-2008, 06:34 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •