forward idle and stalling

so have had the boat running very well after replacing the distributor and having the carb completely rebuilt.

we've been chasing a forward idle forever, and it still is not corrected 100% of the time.

sometimes the engine runs perfect in all categories, and other (like just now)it will sputter and stall in forward idle.

had it out for a ski this morning and no problems.

just went out for a cruise and I could tell it wasn't running right. pulled it back to neutral and then into gear and yep... it stalled out.

so I opened the hatch and started it up to tune the idle speed screw. didn't help... I backed it off almost completely and the idle would hang high. then I got it into gear by throwing it into gear and past idle. got up to speed and gave it some good gas. then it stalled out at speed, which it has never really done before, at least not since rebuilding the carb and new dist.

when it stalled I opened the hatch and could hear a hissing sound coming from the alternator side of the motor, from the top of the engine by the carb or valve cover, riser area. couldn't pin point it.

I pulled the vacume hose off the carb and tried to suck and blow. didn't seem to do anything. put it back on and went to the idle speed screw...
so I backed the idle screw right out after starting it up (no problem starting it) until it almost died and turned it in until it wouldn't stall. put it in gear and turned it in 1/4 turn. then tested it by putting it in neutral then forward and repeat.

was perfect.

then gave it nearly wot and it ran flawlessly. took it back to the dock. shut it down. start, neutral, forward, reverse. no problems and no hissing like before.

I'm completely stumped. how does it run flawlessly one minute and horribly the next without really doing anything?

Check your fuel pressure. Also, even with a rebuilt carb, you can still have some trash in it causing problems. A piece of debris trapped in the needle and set valve. Also, who rebuilt your carburetor and how thoroughly did they clean the metering block?

as per the recommendation on PN I sprayed quick start around the base of the carb and intake manifold.

I am hearing a hissing coming from the alternator side of motor near the carb and valve cover, so this rec makes sense..

what I found when I sprayed it was the rpms dropped drastically, almost stalling, when I sprayed at the base of the carb. but seemed to increase very slightly when I sprayed at the top of the manifold, where it meets the spacer plate.

both sites have helped a ton, lots of great info and I think most people go back and forth, as I have because you want to get as much info as possible. thank you nautique owners!!!

anyways.. as per the original recomendation; rpm should increase and it seems as they did very slightly (hard to tell) when I sprayed along the intake manifold gasket side, but dropped drastically when I sprayed higher up along the bottom of the carb.

I would assume nothing should happen if there's a seal, right? up or down?

what do you think I should order from skiDIM? the gaskets are cheap, but the 2 carb gaskets were just replaced.

could the spacer plate be warped or even the head?

thanks again!

i don't know what was used. the carb gaskets are new from the rebuild, not sure about the intake manifold, but the reaction to the quick start on it was minimal if at all. will replace anyways.

I was going to order the ones from skidim, the pcm ones.. whataya think about them?

just to clarify, there are 2 carb gaskets and 1 intake manifold gasket, correct?

anything I should know or do before or during the install? can I just pull the carb, install and put it back on? or will I have to adjust and tune the carb after? thanks!

this is what I was going to order:

x1 http://skidim.com/prodinfo.asp?number=RM0186
x2 http://skidim.com/prodinfo.asp?number=RM0054B

Answer to the gasket question...two gaskets not three. One between the carb and spacer and the other between the spacer and the intake. Yes...unbolt carb and add the gaskets and bolt it back on. If there was a vaccuum leak and that corrects it...then you will need to adjust the idle screws and idle speed....very simple!
Now the however part!Throttle plate bushings worn? could be...but you said the rebuild was someone who is good, right? He should have dianosed that if it was so...also a new power valve and secondary diaphram are part of the rebuild kit.

Yes..gaskets are cheep! Even though the gaskets a new, they may not be the right ones....there are a bunch of different ones for holleys and can be a bad fit if not the right ones!Go with the Skidim ones and see what happens.
Spacer...yep it can be warped...Check while the carb is off ...lay it on a flat serface(table top etc) and see!
Also...if you have not checked...make sure the PC valve is good(located on the valve cover with a hose that goes to the rear of the spacer). Shake it and see if it rattles...if not , it is bad.

thanks Bob, the last piece of info I got was from a mustang tuner from around my neck of the woods, no boat experience, so he was just giving me his piece on it. I only got 1 reply on PN and it was to replace the gaskets. I appreciate both sites, but do refer here for more technical info and really appreciate the help. sometimes it seems hard to get an answer and I know someone has gone through this, and here it comes!!

I've had the boat looked at by 3 different marine guys, 1 is Pride of Muskoka (the Nautique dealer for Ontario) all were told that there was an idle issue and none have fixed it. The biggest reason I suppose is that it seems somewhat random, but in actuality it only happens when the motor has been run the same day and seems to happen more/worse when the air temp is hotter - very hard to find the pattern (that's me sticking up for shotty work again that I paid $$$ for).

so my guess is that the "pros" didn't run the boat long enough to find the actual problem & my diagnosis has been weak, but we've replaced so many parts to rule things out that it now makes it much easier to determine.

I will check the pcv, I pulled it because I had the motor stall years ago and found it pulled out (looked into what it was lol). I don't recall if it rattled or not, will check!

I was refering to 2 carb gaskets and 1 intake gasket because the spacer plate sits on something. I assumed this was also a gasket.

I am going to order the gaskets and take a look at the spacer plate. I can't seem to find a replacement from skidim...

the one constant on all topics which I'm experiencing is an improper seal or leak at the gaskets... I will start there first.

piss off is I could have bought a new carb for the $ I've spent on it... my fault, I should and now am learning this stuff myself. I just don't have the time or proper tools (slowly accumulating)...

thanks guys, will let you know how the gasket install goes and I'll check out the other recs while I'm at it.

any idea of where to get a spacer plate if I need one?

You can go to the auto parts store and pick up Fepro gaskets...(O'reillys has them)
felpro #60059. That gasket works on three of my rigs 1972 302 and 1984 351. I would assume it will be right for yours....(take the spacer with you and make sure the gasket fits the spacer dimentions).
On one of my 302's I use a #60058 between the spacer and intake(just because I had one sitting arround)...it's a thicker gasket.

You will know soon if you have any other issues once you know that area is leak free.

You can get a new spacer...but the old one can be leveled out(sanded). It may be fine anyway???

Carb removal...while your at it...disconnect the fuel inlet fitting at the carb and you should have a filter screen in the fitting...check it to make sure there is no crap in it.

The process of finding the source of your problem , is to go though a check of all the simple things first before you start dropping a bunch of cash!

What about looking over the coil, some times those go bad.

if the coil was bad would it not also be hard to start?

it fires up like a charm hot or cold.

Kylecraft...your racing ahead here! When your boat is running well but having idle issues , I would say the first place to look is for vacc leaks...you need to determine where they are and stop the leak! Vacc leaks will raise hell with your idle.

Have you even yet checked the spacer...no need to grind the spacer unless it needs it. You can buy a brand new Holley if you wish and still have the same issues if it's not a carb issue!

1)make sure your spacer is not warpped , the carb base is not warpped(if it is...get another) and the gaskets are the right ones.
2)Intake manifold,manifolds or risers...these could be a leak source.
3) and yes it may be an issue with the carb.

I would try to rule in or rule out leaks in the suspect areas before moving to the carb. I have found leaks by either spraying carb cleaner or blowing cigar smoke...a leak will suck the smoke in! Maybe others can offer more help on finding vacc leaks!

If you can rule these factors out...maybe then it's time for a new carb....I purchased a remanufactured marine carb from Allcarbs for about $225.00 and have been very pleased with it!
Lots of folks have dropped cash on a bunch of parts only to find it was a simple fix!

Of course , some times this sh*t is hard to find!!!

Kylecraft,

I ordered this book directly from Holly a few years ago. I found it quite helpful.   Also, there is a lot of free information on the holly site including exploded illustrations of the 4160.

http://www.holley.com/Store/product.asp?ID=36-133

Also, you need two RM0054B gaskets. One for between the carb and spacer and another for between the spacer and the manifold.

Kylecraft,

You will be getting a total of 2 gaskets(no more, no less)Once you remove the carb, it will be obvious where each goes.When removing the spacer, remeber which is side is up.
Removing carb....you will disconnect the gas line at the carb(keep towel with you for gas from line)disconnect throttle linkage....unbolt the four nuts and pull it off!There will be a gasket between the carb base and the spacer...now pull the spacer off and you will see a gasket between spacer and intake.
Once you have done this...check the spacer for to see that it's not warpped...check the carb base for warppage....and check the screen in the gas line fitting you just removed to make sure there is no crud.
If all is well put it all back on with new gaskets and that area will no longer be suspect! Perhaps even solving the prob. If issue still existists....we will more to other check points!
From all you have said ,I suspect a vacc leak(or leaks)and if there are some....it will NEVER idle right period!rule in and rule out!

3-4 years chasing the problem...I assume this was happening before the rebuild on the carb?