Low Speed Needle Valve's Purpose

[68wetboat]

I'm having trouble starting my 68 Johnson 40HP and have checked fuel, tank, lines and pump...now I'm up to the carburetor. I've messed with the "low speed needle valve" a bit. I've turned in a few rotations in each direction but didn't notice anything different when I'm trying to start up. My question IS...does the low speed needle valve have ANYTHING to do with starting or is it just an adjustment to make for fuel intake when the boat is cruising at low rpm's. <br />(low speed needle valve above carb in picture)<br />

<br /><br />Next question. I took apart my fuel pump and ended up having to buy a new one..gaskets were a wreck...being a novice, should I attempt to get a carb kit and try and see if the carb is the problem with starting. (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=2485001433&category=50439) Is this any good. I did learn my lesson the first time with the pump and didn't take pictures when I disassembled it...now I have the dig. cam and will be more careful. Do ya'll think the carb cleaning is do able for a first timer like me?<br /><br />Finally, last random question. How can I check if my spark plugs are getting a good spark. Should I be able to see a spark? I'm graduating Elec. Engineering in a month but when it comes to engines/parts, I'm pretty inexperienced.<br /><br />Thanks in advance.<br />Jason

 

[alcan]

Re: Low Speed Needle Valve's Purpose

Hi Wet<br />Have you ever had this motor running? The low speed needle meters fuel to the low speed circut in the carb. this only funtions when the throtle plate is closed. Begining setting for the low speed needle is 1 1/2 turns out from lightly closed. Works like a fauset. You really should have a repair manual for this work. The nice thing about a manual is it should line you out with the proper procedures and steps to having a healthy good running outboard. Right now you thrashing about in the dark. This costs lots of money and seldom yeilds good results. To test for spark remove the spark plugs and ground them to the block. Turn engine over and observe spark. Congrats on your graduation.

 

[68wetboat]

Re: Low Speed Needle Valve's Purpose

Hi alcan,<br /><br />I got this boat about 2 months ago and it didn't start. I took the back end off and sprayed WD-40 everywhere into the pistons and into the carb. Don't know if that did anything. Next I switched the spark plugs (it was backfiring) and it started right up!<br /><br />I've taken it out a few times and it worked fairly well. Lately though, it dies after a minute of running and now won't start at all. <br /><br />I'll check the spark. I have the Repair Manual specifically for my boat. I also went to the library and picked up a few more manuals for my era of motors. They helped alot. Thanks for the advice.

 

[68wetboat]

Re: Low Speed Needle Valve's Purpose

Oh yeh, I might also mention that it ran great in the beginning, then the boat ran at what seemed to be half speed after a few trips to the lake. It would sputter into full speed for a second and back to half speed.....after that day, it was tough to even get the engine started.

 

[alcan]

Re: Low Speed Needle Valve's Purpose

Hi Wet<br />It defenatly sounds like you need a full Service and tune. Start with a compression test, if that looks good, check the lower unit oil. If all is well procede to the ignition system,points, coils, condencers, plugs etc. Once all is well there move to the fuel system,Clean,repair,reajust the carb as needed. You have already installed a new fuel pump. Once this is covered move to the cooling system, replace the pump empeller,maybe the whole pump,test or replace t-stat if equipt and I believe it is. Do a link a sync, a little greese here and there and you'll be good to go.

 

[68wetboat]

Re: Low Speed Needle Valve's Purpose

Alcan, ...heard what you said and I started my trek to repair.<br /><br />The fuel pump has been replaced.<br />Next you said to test the compression.<br />Top Cylinder: 50<br />Bottom Cylinder: 45<br /><br />Rented a compression tester from autoZone, stems bent while in the spark plug holes...it was tough to get the plugs back in..(maybe stripped some of the hole)<br />Either way, the boat started about 2 weeks ago for the last time so I believe the compression is decent enough to start the boat...I know the head gasket has a little hole in it...I'll get that replaced and try again.<br /><br />Any ideas on the lowest PSI a 68 Johnson will run off...I heard 100 PSI minimum / cylinder. Maybe it was a cheapo tester....is there somewhere else I can rent from? OR maybe take into a boat/car place to check?<br /><br />I skipped ahead and drained and replaced lower unit oil. That stuff was smelly and nasty (old stuff).<br /><br />Next, I thought about ordering new points, coils, condensers....is there 2 of each of those parts for my engine? Looking at the manual..it seemed so. Should I try to take apart the ignition system and look for cracked coils or just buy them and replace.<br /><br />I really want to get the compression up before I spend more money though...or else all seems like a lost cause.<br /><br />Thanks for the help...keep it coming <br /><br />Jason

 

[alcan]

Re: Low Speed Needle Valve's Purpose

Jason If you have a manual you will need to read it. It should explain the proper way to conduct a compression test. If your pistons are hitting the adaptor on the compression gauge, this is not good. Get the correct adaptor. Your test results are not good, they may be false, do to incorrect use of tool or procedeure. How ever, you state you know the head gasket leaks. You will need to rememdy this. At least it will give you an excuse to pull the head and have a peek inside. Follow the systematic tune-up procedure as out lined in the manual, step by step. Always inspect and test parts before ordering new. Do not worry about making repairs until you are fairly confendent of what you have and what you need to make this motor go. A few hours spent inspecting, testing and sorting stuff out is money in the bank for you. Even if the motor turns out to be a total loss mechanicly, at least you will have gained the expirence for the cost of a manual.

 

[68wetboat]

Re: Low Speed Needle Valve's Purpose

alcan, <br /><br />I found out why I lost so much compression. The thermostat was missing when I bought the boat(didn't know this until a few days ago)...so the thermostat valve never opened when I had the boat going on the water (apprx 7 hrs) meaning no water flow and cooling around the piston casings. So a small pinhole from the piston cases developed(flush with the head gasket) into a hole a few millimeters wide...and the hot exhaust melted the outer piston casing...<br /><br />bottom cylinder (apprx 1 o'clock area)<br />

<br /><br />So, I'm having a friend weld the hole and we're going to use a dremmel tule to make the inner piston casing perfectly flush. I am going to install a new head gasket and a new thermostat.<br />I'll then pray a little bit and try to start her up.<br /><br />If it still doesn't start, I'll test/change the points/condensers/coils....b/c I think the fuel system is fine...sprayed fuel in carb and pistons and still didn't start....but first things first....I'll wait till parts get in and install and test<br /><br />You've given alot of good advice. I appreciate your help and time.<br /><br />Thanks<br />Jason

 

[alcan]

Re: Low Speed Needle Valve's Purpose

This type of job is usually better off handeled by the mechine shop. How ever in this case, the age of the motor and all. I don't see where you have a thing to loose. Go for it.

 

[lark2004]

Re: Low Speed Needle Valve's Purpose

if thermostat was missing, then water should always be flowing, hav you checked your impeller yet, no water flow would be caused by a faulty water pump, or blocked passage due to parts of old impeller getting jammed when the rubber falls apart. What condtion is the lower piston in now that it has been overheated, you may find that the piston needs to be replaced if temps got hot enough to melt the block...

 

[68wetboat]

Re: Low Speed Needle Valve's Purpose

I haven't checked the impeller. I will do that very soon. How easy/difficult is it to test for blockages? If I shoot some water from the impeller up to the upper casing and see water flowing, is this a good enough blockage test?<br /><br />I am not 100% sure how the thermostat mechanically operates, but when I disassembled the thermosat housing, the spring was pushing the valve up to the hole where the bottom of the thermostat should lie. This sealed off the hole allowing no water to flow. I'm guessing that when thermostat gets up to a certain temperature, it pushes the valve down and compresses the spring allowing water to flow through the piston casings. I guess I should have been more specific in saying the spring, valve and thermostat casing were in place but the actual "thermostat" measuring device was missing. Does that sound right Lark? If not, let me know...<br /><br />As for the lower piston's condition, I am hoping that the only damage is to the back end. I am aware though that extra damage could have been caused elsewhere in the piston casing or I guess to the piston as well. First things first though, I will replace thermostat and head gasket, test and then proceed based upon results.

 

[lark2004]

Re: Low Speed Needle Valve's Purpose

yep sounds right, I thought you meant the entire thermostat had been removed, Back flush your cooling system to make sure nothing is possibly blocking the pipes, other than that, should be easy enough, Q? is it manual shift or electric. They have diffent water pumps, the electric has two pipes that attach to the bottom of the engine. Also, what model number is your engine?

 

[68wetboat]

Re: Low Speed Needle Valve's Purpose

I'd kill to know what model number I have...I've been looking around the transom plate...can't find a number...any ideas?<br /><br />Also, it's a manual shift.

 

[lark2004]

Re: Low Speed Needle Valve's Purpose

take a photo of the engine, and one of the complete outboard, that will get us in the ball park, other than that there will be a serial number on the engine block, stamped into a welch plug near the top, that may help us track down a model, maybe.

 

[68wetboat]

Re: Low Speed Needle Valve's Purpose

I've got quite a few pics for ya. I have the service manual as well..it gives the following possible model numbers:<br />RD-30 <-- has spring loaded choke, ready pull start, rope only knob on steering bracket or remote control<br />RDL-30 <-- has spring loaded choke, ready pull start, rope only knob on steering bracket or remote control<br />RDS-30 <-- electric start, automatic choke and manual lever<br />RDSL-30 <-- electric start, automatic choke and manual lever<br />RK-30 <-- electric start, electromatic remote control, automatic choke and manual lever<br />RKL-30 <-- electric start, electromatic remote control, automatic choke and manual lever<br /><br />I have electric start AND rope start but manual shift remote control..not electromatic. Judging from that info., I can rule out RK and RKL <L means 5 inches longer><br />I also have a manual lever that has 3 positions "choke off", "automatic", and "choke on"<br />I don't know what "spring loaded choke" means but I'm guessing that I have the manual lever which rules out RD and RDL.<br /><br />So, quasi-educated guess yields...<br />RDS-30 or RDSL-30<br /><br />Asumming I guessed RDS/RDSL correctly..how do I check if I have the Longer model? Are there any measurements I can take?<br /><br />Pictures below...<br /><br />profile<br />

<br /><br />top (w/ pull start removed)<br />

<br /><br />WELDED AND DREMMELED(smoothed) new cylinder ..compare to previous post's pic above<br />

<br /><br />transom mount<br />

 

[68wetboat]

Re: Low Speed Needle Valve's Purpose

alcan and lark...thanks for the help.....THE BOAT RUNS....haven't tested on water...but it started up when i cranked the key<br /><br />just welded that hole on the piston casing and then installed the new head gasket...boy was that easy.....still gonna worry a bit about the cooling system so I don't screw things up again.<br /><br />thanks for being patient and all the advice.<br /><br />jason

 

[lark2004]

Re: Low Speed Needle Valve's Purpose

May just have to test engine temp by hand. I know that with mine, most of the water is recirculated back down the leg and exits underwater (hence the second pipe at the waterpump). So as a result I don't see much water coming out the back. Did your pump have one or two pipes connected to it?

 

[lark2004]

Re: Low Speed Needle Valve's Purpose

May just have to test engine temp by hand. I know that with mine, most of the water is recirculated back down the leg and exits underwater (hence the second pipe at the waterpump). So as a result I don't see much water coming out the back. Did your pump have one or two pipes connected to it?