MarineEngine.com - Your online store for all types of marine engines and boat parts.
PHONE ORDERS
Monday - Friday
9:00 AM - 5:00 PM EST
Click for TOLL-FREE Number
Online Checkout
Special $9.95 Flat Rate Shipping
(800) 209-9624 | Home | Contact | Shipping | Returns | Cart View your shopping cart.
Part Number Search
Shop by engine/drive part number.
Original & matching parts for sale.
Manuals & Accessories
Shop by description, item number
or manufacturer's model number.
Boat Repair Forum Boat Repair Forum   Boat Video Gallery Video Gallery
   
Get instant online access to repair manuals for your Mercury / Mariner outboard. Online Manuals
MercuryMariner
Order printed Mercury / Mariner service manuals — shipped to your door! Printed Manuals
MercuryMariner
Use engine diagrams to find & order parts for your Mercury / Mariner engine. Engine Diagrams
MercuryMariner
Find parts quickly with Mercury application guides. Quick Parts Guide
MercurySierraCDI
Results 1 to 21 of 21
  1. #1
    Join Date
    Jan 2008
    Location
    , Victoria, Australia
    Posts
    157

    Default "Hi guys Brent from Aus again,

    "Hi guys Brent from Aus again, my 40hp merc revs up well out of the water with muffs on, sounds like it has plenty of power, in gear also, it sounds good and revs hard and responsive. When I get it into the water it starts easy enough but when I put it into gear to take off I cant get any more than about 3 knots out of it?? no power what so ever! If I try and throw the lever forward it just stalls! If I do it slowly it just putters along like a paddle steamer, I dont have the same problem in reverse though!! It revs up in reverse in the water no probs but nothing in forwards gear. NB: this is my first time out in this boat (new for me) I have looked at all the linkages and cables but I cant work them out, when I put the controls forward it has about 30% free play before anything happens which has only gotten worse since I tried to adjust the idle. Please HELPPP!!! P.S compression good, spark good and carby checked out ok for blocked slow idle jet. I need help on adjusting/ setting these throttle, idle, power, cables I have stuffed around with them a bit to much i think now i fixed the idel but the rest is kaput!! I can see they all work together in unison but i have no idea how to set them up."

  2. #2
    Join Date
    Nov 2005
    Location
    , il,
    Posts
    2,198

    Default "I have the same motor and fac

    "I have the same motor and factory manual. The reason it had 30 percent freeplay before the carb moved is because they change the timing of the engine first and that causes the engine to acceleratee. This is how its done on outboards. First, with engine running at its slowest speed in gear, the throttle pick up(carb cam link) should be just off the cam. Second, initial timing is 3-5 degreees BTDC. Third, max timing is 27, crank engine and set max timing to 24 with throttle all the way forward, it will go to 27 when running. With the linkage adjusted correctly the butterfly in the carb at full throttle should be almost fully open at WOT.

    None of these setting will help if it has low compression on one cyl. Test compression. Test for spark on each cyl. Remove brass plug on bottom of carb and or remove main jet and clean.
    Main jet is the one to clean, slow idle jet is 5 small holes on side of butterfly. The jet on the top side is the vent jet(changes mixture at full throttle). Float height is even with carb base when held upside down, and the sping on top of float is 3/32. Needle drop in 1/4 on metal arm.
    Email for help, or post follow up.


    Edit, float height is when top arm is even with carb base, bend lower arm to adjust."

  3. #3
    Join Date
    Jan 2008
    Location
    , Victoria, Australia
    Posts
    157

    Default "thanks JB i did compression t

    "thanks JB i did compression test 150 on both cylinders. I have had a bit more of a play with the linkages but I will have a go at your seetings. I also put fresh fuel mix in the tank (drained the old stuff) incase it was also fuel but i am now convinced it is carby as today when i took it down to the boat ramp i had the idel set well and the motor sounded good, i disconnected the linkage from the mounting bracket so I could rev the engine just by pulling on the cable at the back of the boat and it but it sounded laboured when I pulled it quickly as if a major flat spot, not sure if it was starving or flooding the engine I will take the carby off in the next few days and report back once I have tried everything you suggested. i have also ordered a CD Rom repair manual for Mercury 40hp engines from eBay so hopefully that also helps me with diagrams etc.... thanks again."

  4. #4
    Join Date
    Nov 2005
    Location
    , il,
    Posts
    2,198

    Default "check the timing base, linkag

    "check the timing base, linkage is just under flywheel on the left, veiwed from behind. When you advance the throttle it should rotate smoothly and easilly to advance the timing, then the carb linkage moves. To check the fuel pump, squeeze the fuel bulb while running to see if that helps. To check float and needle, squeeze fuel bulb with engine off and at WOT, look down carb, if any fuel is leaking out then the carb needs work. Carb setting should be about 1 1/2 turns on idle mixture screw.
    http://i129.photobucket.com/albums/p...elProblem.jpg""

  5. #5
    Join Date
    Jan 2008
    Location
    , Victoria, Australia
    Posts
    157

    Default "Greetings JB, I checked the t

    "Greetings JB, I checked the timing base linkage on the left it slides freely around towards the rear of the motor when advancing the throttle, but i noticed it only goes about 1/2 3/4 the way around then when i bring the throttle back down it does not go all the way back there is still about 10-15% more free movement back towards the front of the slide. is this because the linkage settings are all wrong? it moves freely and is well lubricated and i cannot see any obstructions or broken parts near it. I have also checked the carby linkage and when i advance the throttle to full the butterfly on the carb is wide open with no free play in the linkage. Once i have stripped the carb and cleaned it all i will attempt to reset the linkages and see if the timing advance linkage works within its full range of movement and report back. P.S is there any guide as to where the linkages should be set ie: should the top and bottom linkage be set at similar lengths on the thread or at opposing ends etc. at present both are wound so 90% of the thread is behind the clamps towards the rear of the engine."

  6. #6
    Join Date
    Nov 2005
    Location
    , il,
    Posts
    2,198

    Default "don't worry about the amo

    "don't worry about the amount of travel, it will work right when set correctly.
    THROTTLE PICKUP(PRIMARY)
    start engine, put in gear, idle, adjust turnbuckel or stop screw (foward screw) so throttle cam is just touching carb lever when at specified timing(3-5*).
    MAX TIMING engine in fwd, adjst screw (top screw)so it is just touching spark advance lever at max timing.
    THROTTLE PICKUP(second)with engine not running, advance max timing arm against top screw, do not move throttle lever, adjust throttle pickup screw(rubber cap) so it is just touching the carb throttle lever.
    FULL THROTTLE STOP (bottom adj screw) with engine off, move throttle wide open and adjust screw so carb shutter is wide open. Make sure carb shutter does not act as full throttle stop.

    Keep starter bolts tight, when they get loose the engine casting will break. Do not exceed 27* max timing. Its buttt cold here, good luck"

  7. #7
    Join Date
    Nov 2005
    Location
    , il,
    Posts
    2,198

    Default "[url=""]http://www.usboatsupp


  8. #8
    Join Date
    Jan 2008
    Location
    , Victoria, Australia
    Posts
    157

    Default "Pulled the carby off today bl

    "Pulled the carby off today blew a bucket load of air through it and the jets, all seemed clean and well, i noticed though when i pulled the fuel line and filter off there was a bit of muck there but surely not enough to restrict any fuel flow. I had a bit more of a play with the setting of the linkages as you described and i think i'm getting there, although i cant seem to get the 1st 30% of the throttle movement to activate the timing advance throttle pickup(primary) first before the (second) pickup starts moving. Mind you I did manage to get it to idle smoothly and when i get it into gear and advance the throttle forwards it revs up and sounds crisp and without sounding laboured, it will be interesting if it reacts the same with the leg in the water. I will continue to have a bit more of a play with the linkages over the next few days and report back. PS: the adjuster screw that is on the throttle spark advance linkage for the throttle is that used for timing advance only or is it a secondary idle adjuster? i wound it back so it retarded the timing a bit at idle and it seemed to run smoother. i noticed on the diagram on the merc parts catalog link it doesnt show it?"

  9. #9
    Join Date
    Nov 2005
    Location
    , il,
    Posts
    2,198

    Default "you say 30% freeplay, is this

    "you say 30% freeplay, is this just moving the shift lever out of neutral? It must shift into gear and then advance the timing/throttle 2nd. When tring to accelerate the carb will open slightly, the timing will advance, and then the carb will open fully once you have reached max timing. There is only one idle speed adjustment, that is a screw in front(philips) with a 7/16 lock nut. That screw was not part of the procedur I sent you, but should be adjusted to maintain a slow idle. All adjustments are to be done in gear and running unless otherwise stated. The reason for this is to prevent the engine from accelerating when you shift from neutral to fwd. If you set the linkage in neutral, there won't be enough freeplay. Base timing 3-5, max timing 27."

  10. #10
    Join Date
    Nov 2005
    Location
    , il,
    Posts
    2,198

    Default "I just re-read your first pos

    "I just re-read your first post. It runs fine in reverse because the engine only changes the timing and doesn't open the carb while in rev. This indicates a fuel problem, runnig lean. Open the idle mixture screw(right side of upper carb) 1/4 turn and try again. Be sure main jet is clear of dirt."

  11. #11
    Join Date
    Jan 2008
    Location
    , Victoria, Australia
    Posts
    157

    Default the 30% freeplay does shift th

    the 30% freeplay does shift the engine into gear the engine revs do not go up. i was looking to see if when the forwards gear was engaged that the timing would also advance slightly but obviously it will only advance further when more acceleration is given. I have been adjusting the linkages with the engine in gear at the first 30% without it opening the throttle then checking it at WOT with the engine off its nearly at the stop screw and the carby butterfly is wide open so i'm nearly there.as far as timing 3-5 degrees i am yet to locate an significant timing mark on the flywheel or near it?

  12. #12
    london marine's Avatar
    london marine Guest

    Default The lever on the control box f

    The lever on the control box first shifts the engine without giving throttle that is the way it is supposed to work! Now you can put your own timing marks on the flywheel just a bit of math and measuring involved. You need to be careful in the " I think I will adjust this " approach as it can cost you a lot of money in the long run.

  13. #13
    Join Date
    Nov 2005
    Location
    , il,
    Posts
    2,198

    Default "the timing mark is to the rig

    "the timing mark is to the right of the switch box, its a black plastic pointer, it could have been broken off at some time. there are timing marks on the flywheel and the top plug is #1cyl. As london marine said, don't be guessing at this. Too much timing will destroy the engine quickly. If you have the timing close, put a load on the engine and briefly have someone go to full throttle, check the timing, no more than 27* on 87 octane. If I remember the flywheel has a 0(tdc) then a couple of slashes, best guess here, thats why its 3-5*"

  14. #14
    Join Date
    Jan 2008
    Location
    , Victoria, Australia
    Posts
    157

    Default When you say NO more than 27 d

    When you say NO more than 27 degrees advanced on the timing is this measured by timing light once top dead center has been established or does it have to be measured and marked out on the flywheel?

  15. #15
    Join Date
    Nov 2005
    Location
    , il,
    Posts
    2,198

    Default "this should be done with timi

    "this should be done with timing light, and is marked on the flywheel. If you have a manual start model the timing mark(pointer) is part of the pull start casting. If you are having trouble understanding this wait for the manual."

  16. #16
    Join Date
    Jan 2008
    Location
    , Victoria, Australia
    Posts
    157

    Default "It just so happens I bought a

    "It just so happens I bought a new timing light a while ago so I can now put it into use. I do have the pull start option model i'll have a good look over it to establish the correct markings. Well I'm off for a 2 week holiday from work now for fun in the sun, Summer here in Australia averaging 35-38 degrees celcius everyday, so I'd better get this boat sorted so I can get on the water pronto. Thanks for all your help JB it has been invaluable. I will post again in the next few day to let you know how I got on."

  17. #17
    Join Date
    Nov 2005
    Location
    , il,
    Posts
    2,198

    Default "front right corner I think fo

    "front right corner I think for timing slot. 5-8 inches of snow to be here tonight, fun fun fun"

  18. #18
    Join Date
    Jan 2008
    Location
    , Victoria, Australia
    Posts
    157

    Default "I completely gutted the thing

    "I completely gutted the thing today found water getting into the bottom cylinder removed motor from leg and found the gaskets all dodgy cleaned areas and replaced gaskets put it all back together and replaced powerhead water jacket cover gasket and the one on the coils. adjusted all settings and fired it up, it idled well revved well and even had power with water going in the system. the water had been getting into the bottom piston when it was on its backwards stroke as the water was getting sucked in because the gaskets had perished, and causing it to run on only one cylinder. all sealed up all fixed i'll be out on the water tomorrow"

  19. #19
    Join Date
    Nov 2005
    Location
    , il,
    Posts
    2,198

    Default nice job!

    nice job!

  20. #20
    Join Date
    Jan 2008
    Location
    , Victoria, Australia
    Posts
    157

    Default "update, it spat the impeller,

    "update, it spat the impeller, overheated and blew the gasket betwen the power head and the mid section again. got towed back to boat ramp, got home and found a heap of muck in the bottom of the leg before the impeller which had blocked the impeller inlet. Iv'e had it going again and compression is still strong no damage caused as I shut it off as soon as i felt there was a problem. I have the top of the motor off again redoing the gaskets, I have also gutted the midsection and lower leg and flushed all water jackets out with high pressure water and removed all debris that was lost and floating around in system. New impeller kit installed(again after two weeks) this time if it gives me grief I'll undo it from the transom and tip it into the drink. Although it would make a good anchor!!"

  21. #21
    Join Date
    Nov 2005
    Location
    , il,
    Posts
    2,198

    Default "check the gasket on the exhau

    "check the gasket on the exhaust transfer plate, the plate behind the linkage(left side). there are 2 gaskets there that allow the exhaust/ water to mix if bad. Water pump pieces like to get trapped there also. Pull me out a piston before you kick in the pond, I need it for engine #2."

Similar Threads

  1. 1983 40HP Mercury Water Pump complete
    By bearclawchris in forum Mercury Mariner Outboard Archive
    Replies: 1
    Last Post: 07-09-2008, 12:11 AM
  2. 40hp mercury 1983 gearbox trouble
    By brentle in forum Mercury Mariner Outboard Archive
    Replies: 6
    Last Post: 02-17-2008, 03:13 PM
  3. Throttle problem Inside Engine Mercury 1993 40hp
    By kozak in forum Mercury Mariner Outboard Archive
    Replies: 2
    Last Post: 05-30-2007, 09:36 AM
  4. 1983 Mercury 40hp outboard lower unit question
    By L.Marquith in forum Mercury Mariner Outboard Archive
    Replies: 7
    Last Post: 04-20-2004, 08:21 AM
  5. Looking for a Mercury Shop Manual for 1983 40hp
    By L. Marquith in forum Mercury Mariner Outboard Archive
    Replies: 2
    Last Post: 03-12-2004, 11:00 AM

Posting Permissions

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