1984 - 351W - High Idle, Mechanical Advance Stuck? |
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Tim_2001PNW
Newbie Joined: September-26-2017 Location: Covington, WA Status: Offline Points: 12 |
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Posted: January-27-2018 at 2:47am |
Hi Everybody,
Trying to figure out my next move. I have an 84' 2001 with the 351W and it runs really well but seems to idle high after warming up and running for a bit. When I bring down to neutral my idle stays at or slightly above 1,000 rpms. Also there is at times some slight hesitation when hitting the throttle (this could be as easy as a carb adjustment though, haven't really looked into it) I just got the boat in late September so only out a handful of times. My questions 1. At what RPM should it be idling? When warming up its around the 600's. 2. I have been trying to read up, could the mechanical advance be stuck after running and not springing back at idle? and if so, what would be the best way to resolve the issue? 3. How do i determine the engine rotation? Any thoughts and or other threads to read would be much appreciated. Thank you! |
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Jonny Quest
Grand Poobah Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2858 |
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Welcome. To answer your questions:
1. I like the idle to be 650 to 750 rpm. Any lower and my transmission damper plate will chatter. 2. Your mechanical advance could be hanging up. Might be time to give some TLC to the distributor. Everything should move freely and you can take the cap and rotor off and see how things look inside. 3. Engine Rotation. Based on the year, it's most likely that you have a reverse rotation engine. There are a couple of double-checks that you can do. Take your coil-to-distributor wire off. Bump the engine with the starter. When at the driver's seat and looking aft, a reverse-rotation engine will turn counter-clockwise. Most likely you have a Velvet Drive 1;1 transmission. If your propeller is a right-hand rotation with a 1:1 Velvet Drive transmission, then you have a reverse-rotation engine. Your "hesitation" on accelerating could be a balky carburetor -- particularly the accelerator pump. Might be time to give some TLC to the carb by way of a rebuild. JQ |
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2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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Along with what JQ said about the distributor, I'd also look at the carburetor when the idle hangs high.
When it's idling high, with the engine still running, see if you can push the primary linkage farther shut. If you can and the idle goes back to normal then it's time to look at the return spring on the carburetor primary shaft or the separate return spring that is a lot bigger and goes from the linkage to the intake manifold or a bracket on the manifold. The spring(s) could be weak or the throttle cable is not aligned very well causing the linkage to hang up.( Or the shaft itself is binding) You can also try pressing on the secondary linkage to make sure the secondaries are against their stop and not hanging open slightly The picture shows the primary linkage where the throttle cable hooks up,and also the separate spring and the secondary shaft linkage with the bent rod that goes between the primary and secondary linkages to insure that the secondaries are never more open than the primaries. You can't see the spring that goes around the primary shaft in this picture, it's behind the big plate that the throttle cable and other visible spring are hooked to. By the way, in the picture above either the primaries are open some or the link arm to the secondaries is way out of adjustment. Here's what it should look like at idle |
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Tim_2001PNW
Newbie Joined: September-26-2017 Location: Covington, WA Status: Offline Points: 12 |
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JQ
Thank you for the input and I will open up the distributor and take a look. If need be I will post some pictures. Appreciate the explanation on the rotation that makes sense and seems easy enough to figure out. It is the velvet drive 1:1. Keno I will take a look at the carb as it sits and see if anything is out of the ordinary and there again post pictures. |
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Tim_2001PNW
Newbie Joined: September-26-2017 Location: Covington, WA Status: Offline Points: 12 |
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Keno
Thank you for the input |
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3333 |
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As keno explained very well, i also suspect the secondary hanging open.
But the best solution is not to rebend the rod in most cases. now assuming the throttle cable end is adjusted to provide modest pressure to positively close the primary against its idle stop... Likely your idle throttle setting has been opened to far to make it idle some, to compensate for a clogged idle fuel circuit, making do with 'idling' off the primary transition slots that get fuel from the mains vs the clogged idle fuel orifices. This condition makes a properly bent secondary rod, go slack and permit the secondaries to hang open after a good romp. As an indicator, the condition often clears itself after a shutdown, after the ATM pressure on the throttle plates and shaft, has less effect from the removal of manifold vacuum. Also would answer the hesitation issue too |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
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Tim_2001PNW
Newbie Joined: September-26-2017 Location: Covington, WA Status: Offline Points: 12 |
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GottaSki, You are correct the condition clears itself especially if the boat sits for a little before going underway again.
How would you work to clear idle orifices? or where would you direct your attention to solve the issue? |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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Your best bet as far as the carburetor goes is to spend 25 bucks or so on a Holley Carburetor manual. ( the old fashioned paper version)
Most of them cover a bunch of different Holley's but they all have sections on a 4160 explaining theory of operation, overhaul and tuning. Lots of pictures to look at to help you understand what parts are where, and good explanations of each of the circuits. A much better learning experience than trying to get it explained over the internet Just do a google search on "Holley carburetor manual" and there are lots of choices. As an added bonus, it's great bathroom reading material And..............don't forget about inspecting your distributor too. |
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Tim_2001PNW
Newbie Joined: September-26-2017 Location: Covington, WA Status: Offline Points: 12 |
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Let the reading the begin, i am sure there will be some more questions to follow! Appreciate the help!
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MourningWood
Gold Member Joined: June-13-2014 Location: NorCal Status: Offline Points: 886 |
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To the op:
How many hours on the boat? Another possible cause of your symptoms as described is worn throttle shafts (carb base). They worsen with a hot motor. |
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1994 Ski Nautique "Riot"
1964 Dunphy X-55 "One 'N Dun" 'I measured twice, cut three times, and it's still too short!" |
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Tim_2001PNW
Newbie Joined: September-26-2017 Location: Covington, WA Status: Offline Points: 12 |
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There are around 1,250, what would that entail?
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SNobsessed
Grand Poobah Joined: October-21-2007 Location: IA Status: Offline Points: 7102 |
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Tim - You can check for vacuum leaks (including worn shaft) by spraying carb cleaner on the suspect areas. If it is leaking, even will sound different for a few seconds.
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3333 |
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The idle fuel orifices are in the metering block and behind press plugs that you don't wont to remove.
A thorough cleaning and compressed air check are in order. Teh orifices are so small the difference between plugged and not, is really challenging to resolve. Also the state of fuel filtration had to be considered for the fix to persist. Basically, compressed air to the idle mix screw (hole) should flow out two ports, one to the idle air bleed on throttle body side, one to below fuel level on bowl side. |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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Tim_2001PNW
Newbie Joined: September-26-2017 Location: Covington, WA Status: Offline Points: 12 |
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Thank you for that explanation, makes sense. I will start working on it once it warms up a little here in Washington!
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Tim_2001PNW
Newbie Joined: September-26-2017 Location: Covington, WA Status: Offline Points: 12 |
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Started to take a look at the issues and from just looking around the carb the link arms to secondaries seem to be where they need to (without running just looking). Looked at the distributor found out i have electronic ignition and looked below and the mechanical advance seemed to function properly. I did look at the choke and it was not connected properly. I first tried to just move the choke and it did not move the butterfly at all. As it sat butterfly was fully closed. I took off the choke mechanism and re hooked and adjusted the butterfly to be slightly open. I am going to make sure it has +12V probably today but this might help. I will continue to update once I start the boat here in a couple weeks as some of the recommendations involve the boat running.
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Tim_2001PNW
Newbie Joined: September-26-2017 Location: Covington, WA Status: Offline Points: 12 |
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Thank you for all the replies. Was running it on the fake a lake last night after a valve cover replacement and found that my linkage was getting caught up and not coming all the way down to the right idle. IT was getting caught right at 1,000 rpms. Some adjustments and it is down to where it needs to be. To the lake next to test it out.
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