Help with '81 Nautique engine (Ford 351)

Hello everyone,

I have a 1981 Ski Nautique (recently acquired). It has a little over 900 hours on the original Ford 351 (the Pleasurecraft variant). The engine has been stalling at idle, but only once warmed up. Symptoms: 1.) When the engine is cold, it starts up and idles without issue. It runs beautifully at speed (approx. 2400-2600 rpm). Once the engine has warmed up (after a run wakeboarding or so), the engine will not idle. It immediately stops under about 600-800 rpm. If we let the engine cool (Say 10 minutes or a little more), it'll start right back up. If we don't wait, it won't start without a lot of revving and if we let the rpm drop below 800 or so, it dies. The temperature gauge never registers over about 170 degrees (seems low to me), and it never seems like the engine is overheating (as long as we keep going the engine has no trouble.. it's only at idle or low speed).
It should be noted that I do not yet have electronic ignition (I will be adding this soon\ anyway), and the carb is the "7163" Holley 4 barrel (trying to add any useful information).
I'm wondering if anyone has seen behavior like this and what the solution might be. I considered vapor lock, but I didn't see any fuel lines close enough to the engine that they should heat up. I'm currently running HEET through the fuel (a bottle per tank), but that hasn't helped thus far.

Thanks for your help.

sounds like the idle may just need to be turned up a little most carbe v-8s should idle@700.

I am sure a good tune up would not hurt espically since the boat is new to you.

check to make sure your choke is all the way open at hot idle.

Temp of 170 sounds perfect remember you are using the biggest radiator in the world.

I would lean towards a carb issue but it shouldn't really be heat dependent, thinking more like coil or something but if so it shouldn't matter on rpm etc... I to am curious what position the choke is in.
I believe the spec. for temp is 160-180 depending on which thermostat your using.

idle/choke/mixture settings for sure. temp sounds good. Congrats on the boat.

check the impeller if you haven't. your temp doesnt' sound bad at all, just something to check/replace at season start.

(Message edited by denverd1 on June 19, 2007)

Power valve! Sounds like it is running richer than rich. Does it blow black smoke out the exhaust?

Peter,

The thing is, NO SMOKE. Ever. It sounds beautiful too. THe ONLY issue is when it is hot, no idle and no start until it's cool (or it'll start with some revving, but dies if I try to drop it to neutral in order to put it in gear)....

How about a leak in the intake manifold? Something dependent on heat, but that won't really hurt performance when hot and at running speed (2400 rpms)?

it sounds like the idle. it runs fine when cold b/c the choke is open. once its hot turn the idle screw in (clockwise) and bump the rpms to about 800.

but when messing with the screw only turn it maybe about 1/8 to a 1/4 turn then rev the motor up and let go to see where it sits.


and if you want to get into the air fuel mixture you can too. but if it doesnt load up then dont mess with it

You are looking at one of a few things… First I would look at the carburetor. Generally speaking, you will probably have to rebuild that thing every few years to keep your boat running right, so you may as well just do it now. If you want to just check your power valve like Peter said in the previous post, you can find the mixture screws (one little flathead screw on each side of the carburetor) and turn them both in to until they stop. It should be about 2 to 3 turns. Remember how many turns you go because you will have to back them out to the same exact position. Do not screw them in to tightly. If your engine dies, then you probably have a good power valve and do not have any other obvious leaks in your carburetor seals. If it does not, then you need to start troubleshooting a little further which will probably lead to a rebuild. ($30.00 for the kit + labor) If the power valve is bad, you can just get one of those from the auto parts store for $7.00. If you end up getting one of those, send me a private message and I will tell you exactly which one to get.

If you really want to get into checking the power valve, you can take off the fuel line, pull off the 4 bolts in the forward (front of the boat) float bowl, pull off the metering plate, and the float bowl, and check the power valve by sucking on it with your mouth. I would suggest wiping off all of the gas first. If you can move it by sucking on it, you have a good power valve. Make sure you do not rip any of the gaskets!

The second thing that I would check is only an issue if you have converted your ignition from points and condenser to an electronic ignition. (I am putting this in the post for someone who may have this problem in the future) If you have switched to an electronic ignition, there is a resistor that is prior to your coil that you probably need to eliminate. I had this problem on my boat. I searched and searched. I had the carburetor rebuilt, replaced the ignition coil, wires, cap, rotor, plugs and wires before someone told me about this resistor. This resistor can usually be found under a plastic cover toward the back of the boat. Mine was white and was about 3 inches long and was surrounded with a ceramic type material. I do not know why all of the sudden this resistor became a problem for me because I had the electronic ignition for years without a problem, but after I eliminated it, the boat ran fine! When you do decide on getting an electronic ignition I would suggest getting the Pertronix kit. It works well.

As for your choke, your carb has an automatic choke. There is a circular thing on the side of your carburetor with two wires attached to it. (It is located on the driver’s side of the carb) There is a spring inside the circular case and when you turn the key to the accessory position it applies a voltage to the spring heating it up and opening the butterfly valve in the throat of the carburetor. From when you turn your key to the accessory position, it should take somewhere under 5 min for the voltage to heat the spring enough to open the choke (butterfly valve) to the warm position. When your engine is warm (170 or so is where mine runs) the choke should hold the butterfly valve open. You can adjust this by unscrewing it and twisting the entire case to the spring clockwise or counterclockwise depending on weather you need the butterfly valve to be more open or closed.

Give us more details on how rich the engine is running… Is there black smoke coming out the back when it is idling cold? Does it smoke at any RPM? Is the smoke white or black?

Definately NO SMOKE at all. At any speed. White or black. I most definately kept an eye for that and I'd smell it instantly. I'll take a look at all that when I get back from Philly (work trip). Thanks for the excellent detailed post! I may PM you for more info.

Thanks!

i would say the idle is low... mine is about 800-900

i have a 84 351 SN2001 and my temp is never higher then 160.. once warmed up.. will get to about 165 170 before thermostat opens.. but never higher then 160 after that..

I would start by rebuild of carb. I would think the carb is most likely a 4160 - fuel bowl on either end, the front will have metering block the rear will not and look for a fuel transfer tube - a holley trick kit is around 80 bucks at a decent auto store. I would then take a look at the choke once the boat warmed up - make sure flap is open all the way - if it is not then you will need to fix this problem. Also, one thing to consider is pull off the aircleaner/flame arrestor and make sure to clean the air bleeds out real good - I always get some carb cleaner with the little red tube and start sprayin just be careful every once in a while the cleaner comes back at you and always gets in the eye it'll sting for a min or two. I would change the ignition coil out I actually think this is the main culprit without being able to see your boat/engine first hand. I would also consider changing the fuel filter just to be on the safe side.

I would then tell you that if this does not fix the problem you might have a cam/lifter issue, flattened cam lobe or collapsed lifter.

How is a collapsed lifter or flattened cam lobe effect by heat like he is saying.

Dont scare the guy!

Brian, try going over to CorrectCraftFan.com too. There you will find a bunch of motorheads that know your motor well.

To me...sounds like you need to tweek your choke and bump up your idle. This is assuming your timing is correct too. A sticky mechanical advance can do this as well.

Remember, divide and conquer. That is the troubleshooting mantra of every pro.


(Message edited by derby on June 19, 2007)

I am assuming a hyd. cam and lifter combo. I have observed cars with similiar characteristic's when they heat up.

I have had mech. adv stick and the idle just stays up and won't come back down until you shut the motor off. I would throw out the mech adv. theory.

I would also point out the motor maybe 26 years old and has 900+ hours and a hyd flat tappet is softer than a roller style cam. Why be scared of a simple cam and lifter change? What maybe 300 bucks total if you do it yourself.

I forgot about the sticky mechanical advance... Even if you think this is not the problem, it only takes 3 seconds to check, and you should probably oil it while you are down there. Here is how you do it…

Take off the distributor cap. (You should be able to do this without taking off the wires) Lift off the rotor. Do not worry about where it (the rotor) faces because it will only go back on one way. The center of that post is hollow and there is usually some sort of felt or cotton in there. Lift out that cotton or felt and put a drop (one drop) of oil down that shaft. Replace the cotton or felt. Since you said you have a points and condenser setup, you will need to look behind those, so pull them out. They should be mounted in there with a few screws or something. Below that are two springs. (different sizes) Each one of those springs attaches to a weight, one on each side of the shaft. This is what changes the timing depending on how fast the rotor shaft is spinning, hints the mechanical advance. You should be able to turn the rotor shaft just a little to flex the springs in one direction. The other direction will be like it is running up against a brick wall. I would not use tools to do this like I did my first time because you will probably break some of that plastic like I did when I was jacking around with my stuff. If it is really dirty down there, it is possible that the springs are not pulling the weights back in fast enough which would change your timing and cause your engine to die, maybe. Just make sure it is clean down there and that it appears as though things can move properly. That would be an easy free fix if it was the problem!!!

^ Great tip...except if ithe mechanical advance is frozen, rebuild the distributer. Cleaning the gunk out with a Dremel type tool and brake and parts cleaner, then greasing it, will be a more permanent repair. Plus oil being flung inside a distributer cap, could cause a miss fire. It would also be easy to check timing with a timing light, yet as suggested above, even simpler is to visually inspect the advance mechanism.

Often when a power valve gets a hole in it, they will run great except at idle. What happens is it will run really rich in the low end, causing a stalling condition. All it takes to blow a power valve is a single backfire through the carb.

FWIW that motor should idle at 500 RPM's smoothly.

When you do get it fixed the best way to adjust the carb is in the water, boat in gear then out of gear rev it, drop it back in gear, then rev it in gear, and back to idle, until you find the sweet spot for all the screws where everything runs just right. It might take a few trips out on the local water way to get it 100% dialed, especially if it is your first time.

Actually the PCM idle spec is 600 in gear. Any lower and the transmision load will kill it.

Out of gear that's around 900 on my boat...er, old boat.

If you suspect the distributor, which I really doubt is the culprit, I have one that you can borrow to test out.

its 650 for the 351 in the 2001. trust me, i got the manual, and have had to adjust it numerous times. seems that everytime we add a ridiculous amount of weight, things get off

Hate to be a stickler but page 9 of my original PCM manual states 600 rpm in forward gear.

No I did not run to get the manual. I have it sitting on the dining room table waiting for the new owner to pick it up.

However, I usually run it a little higher too because of the tendency for the idle to fluctuate. I'd rather it be higher then lower for the same reason as this post.

what nbeihl wrote sounds right. Only thing left out might be the fuel pump. MIne went out, It was pumping, but not enough pressure. after a carb rebuild, and new fuel pump. Im running strong.

(Message edited by rem_pss308 on June 21, 2007)

Geez, when I learn to type what I am trying to say maybe it will make sense to others...

The engine idle speed spec is above what it "could" idle at smoothly when everything is running correctly. The engine should be able to idle very low and still be smooth. I can get my big block to idle down into the mid 400's and still be smooth. It gets low enough you can hear each cylinder hit. Ever hear a flat head run at less than 150 rpm's? If so then you will understand what I am trying to say.

The spec is 600 in gear, but that also needs to be set with some load in the boat. Getting it dialed will take some finessing too, as I mentioned above.

If the fuel pump was bad it would have a lack of power in the higher speed range, or slowly stall out at idle as it ran out of gas. Restart would be next to impossible. Plus the aux line going to the top of the carb would be full of gas, and/or gas in the oil.

The fuel pump on your boat is a mechanical fuel pump and it has two diaphragms. This is for safety so that you do not get caught out on the water with a bad fuel pump. The two diaphragms are made of different material if I am not mistaken. There is clear plastic tubing that comes out of the side of the fuel pump. If you could cut open this pump, the clear plastic tubing would be trying to suck gas between the two diaphragms. The goal would be that if there is fuel in this line, you know that you have lost one (the first) diaphragm and you should probably start thinking about getting back before you do not have the ability to pump gas to your engine. You may not notice a problem operating your boat even when the first diaphragm is leaking, but you are soon to have a problem. I am not saying that if your clear plastic tubing is dry that you do not have a problem, but it is usually a good indicator and a quick check. I went to Autozone and got an inline fuel filter ($3.00) and inserted it inline right before the fuel pump. Doing this allows me to see if I am getting gas right away and helps when I am troubleshooting.



I have had my boat for a while and I have had every problem in the world… most of my problems have been owner educed as I am always jacking with something to learn about it!

Oh, as for the idle, I tune mine to about 621RPM and that is in REVERSE IDLE!!

Just giving you guys a hard time... I put mine where it sounds good and I try not to spend to much time idling around, I'd rather be wakeboarding!

620-621 what ever it takes.

Quick question:

If it turns out I have to re-build that carb.. how can I figure out which model I have? It's a Holley 4 barrel, but I can't find the model number. I've heard it's likely to be a 4160, but on the carb itself, I couldnt' find a number like that. I saw 7163... where should I look?

thanks!

Take a picture of it and post it up.

I'll do that when I get a chance

Hey, couldn't get a picture, however I have a quick question. It looks like the carb will need a rebuild, so I looked at the Holley on the boat and the only list number I could find was 7163... now I thought that was a big-block carb number and I have the 351....

Looking up the list number I did see it associated with the 4160 carb. odd?

Sound like Nbeihl has all of the bases covered. I wish I had consulted with him a long time ago.

IMO, it sould like a vaccum leak. I would rebuild the carb and put new gaskets on. They should come with the rebuild kit (about $50).

I think all of the carbs for the small block engines for those series of years was the Holley 600 cfm (4160) marine carb. I believe the 4150 is the same but for cars. That was for PCM and Indmar engines.(The 4160)

I would higly recomend just buying a new carb. I had mine rebuilt a couple of years ago and it only fixed it for 2 summers. Now I shelled out for a new carb, and it runs great. (But around $500-600) ouch!

My boat did the same exact thing.

1. started and ran fine
2. Ran great at high rpms
3. died when close to idle after running at crusing speed, but it would always start back up.

This is why I don't think it is and electrical or distributor problem.

My old boat had a ford 351 winsor on it, the smae as yours, my new boat has a gm 350. The reason I say this is that I had a distributor problem with my 351.

I would not recomend pulling off the white resistor. (The white thing on the back of the block). It is either in circuit before or after the distributor. (I think after)is is a converter/resistor 6V that deals converting a 12v sytem to 6v the distributor. Something that Ford does that Chevy doesn't do. If you remove this you will likely fry, he pick-up in the distributor.

I would also recomend buying the PCM Marine Engines Shop Manual, you can get this at www.skidim.com for about $25. It has the theory, and oem parts numbers, and how to install and maintain anything put that engine.

To find exactly what kit you need, you need to look right here...



Once you have the number, you can compare it on www.skidim.com

If your number is:
7159, 9393, 50418, 80264 and 50462, 9128, 9394, 50379, 80262, 7128, & 50399
You need the 4160 HOLLEY 302/454 rebuild kit.
Item 0419 from Skidim @ $45.00

If your number is:
9128, 9394, 50379, 80262, 7128 and 50399
You need the HOLLEY 302 4V rebuild kit.
Item 2004130 from Skidim @ $59.00

If your number is:
7163, 9392, 50419, 50463, 80265, 50469, 50469-1, 80456, 80319-1, 75009-1.
You need the 4160 HOLLEY, 351, 350, 5.8, 5.7 rebuild kit.
Item 0421 from Skidim @ $41.98

The kit should have parts something like this...



When you do purchase this stuff, make sure that you get the gasket for the carburetor spacer. It is only $4.00, and the part number at Skidim is 1127.



It has been said that you can use the kit from an auto carb, but the seals are made of a different material and may not last as long in a marine environment. I have not tested this theory, but they say it is possible.

As Craig said, I had to get my carb rebuilt every 2 years or so. After paying to have it done and it taking a weekend away from my skiing, I decided to try to do it myself and it was actually easy. If you have air tools with a wire wheel (maybe even a drill with a wire wheel attachment) and some carb cleaner, all you have to do is clean everything really well and put it back together the way you took it apart. If you have any questions, just post to this thread. I will check it each day. I have nothing else to do in the evenings… I am deployed to the Middle East for half of the summer so I have to live vicariously through you guys while my wife takes my boat out every day!!!

I just ordered that kit from skidim for my 1980 Ski Nautique with a 351 Commander, my carb is the same as yours, ID is 7163 but the carb model is HOLLEY 4160. you have to get the repair kit, the base gasket, 4 new screws for the primaries and other 4 for secondaries, and the 2ndary diaphragm, total for this is around 65bucks using some discount code, plus shipping.

I also bought the repair kit for the distributor last month, also changed coil, plugs and cables.

Boat is running much better now, next thing to buy is an ACME 540 or 542 prop.

Luciano,

Do you have that discount number? I'm looking to buy from the same shop, the same set of equipment..

Thanks so much everyone! I did replace the distributor (it was cracked and a little fried) but upon doing so I did discover that the previous owner had added electronic ignition! That's a nice surprise. Now, it was the Petronix, and I've been told that those can get fried by heat (apparently the purolator ones are all metal and don't have the same issue), but it's still nice!

Hey Nbeihl,

Air Force eh? What are you flying?

Thanks again for all the detailed responses. I'm starting to get this boat in shape and it's a really fun process for someone who's never really been a gear head (before I was just interested in the boarding, now I enjoy tinkering with the boat... plus my girlfriend loves riding--everyobody wins!) I had a friend look at the boat and after tinkering he thought compression leak as well. I'll start with the carb, and if that fails, move to the intake manifold.

Thanks! Take care everyone!

Currently I am flying the Lear35 for DV's, but I am up for an assignment and I am 99% sure that I am going to the mighty AC-130...

SWWWWEEEET! The A-130 is HUUUUUGE. I walked in the cargo bay of one of those beasts. Congratulations if you get to start flying them.

Hey nbeihl, can you post pics of your American Skier?

Hey nbeihl,

I sent an email to the accotn you have on your profile.... just making sure that's still your email.

Brian I responded the PM to the hotmail account in your profile.

Thanks, Luciano, I got your email back, but I couldn't figure out where to get the discount codes...

That is me... I responded to your email.

So, rebuilt the carburetor. At first, big issues because the gasket between the 2ndary bowl and the main body was lacking something in each corner. We had to add to the gasket, but once we did, it worked like a charm! The power valve was in bad shape, but otherwise the carb looked decent, so I would guess that was the issue.

I just re-finished the teak on the swim deck and the rest of the baot, and she looks Great!

Thanks everyone for all the help.

One last thing... Once you have the entire carb together, you can search for leaks like you are talking about by spraying carb cleaner along the parts that are connected by a gasket. Do this while the engine is idling, and if the engine increases in RPM you know you have a leak!

Gteat advice Nick! Thanks again!