Yamaha 50 hp Four Stroke, difficult Starting " Cold "

Hoggy

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Feb 18, 2004
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I have a Yamaha 50 hp Four Stroke O/B ... year of manufacture 1996, its a carburettor model, 4 cylinder.<br />Problem is when cold, it’s very difficult to start, taking many attempts, as of yet it has always started, but with difficulty. When hot there isn't a problem starting.<br />There appears to be no fast Idle when it eventually catches, in fact it barely idles, struggling to fire on four, given a minute or two its raises and from then on runs fine, never giving an ounce of trouble all day, starting fine as many times as I try. <br />I'm supposing there is a problem with the cold start enrichment system and or Idle up system ... anyone shine any light on this problem? ... thanks in anticipation, …… Hoggy.
 

rodbolt

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

hello<br /> without actually looking at your engine I willgo out on a limb. the F50 and T 50 motors I see have a dual cold start function. it has a solinoid tyat acuates anytime the key is in start position. and it has an electro thermal plunger that assists with cold start but allows less choke when the ambient temp is higher. sounds like one of them is either not working or out of adjustment. this motor has choke butterflys and needs periodic adjustments.<br /> this set up is fairly complex and has many joints and linkages but can be done if you use the proper manual.<br /> sounds like your on the right track with the cold enrichment. and this motor has no fast idle per se. it is controled by the choke solinoid and the electro-thermal plunger. as the choke opens it allows the throttle plates to close.<br /> good luck and keep posting
 

Hoggy

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

Cheers rodbolt .... I certainly intend on going down that road you have kindly suggested. With regards to tracking this fault, I will check out supply is getting to the solenoid and if the component is functioning correctly. Basically if I can locate a manual this would undoubtedly be a great help, I have on the net found CLYMER YAMAHA 9.9-100HP 1985-1999 OUTBOARD REPAIR MANUAL code # B788 .... the engine in question being the “ F50 “ model<br />I'm pretty sure this is the correct manual for the afore mention engine, would you suggest this is the best one to go for, not with standing the works manuals are inherently more comprehensive and expensive if indeed I could locate one in the first place!<br />Off the main issue, this site is the best most knowledgeable site of its nature I have ever come across, it’s a minefield of knowledge, thank you for such a swift response, and I will post how I get on, or not! … with this problem, and will also keep looking in on this site regularly ….. cheers again ;o)
 

bossee

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

Hi,<br />You should be able to buy a orginal "Service manual" for Your 1996 Yamaha F50 4-stroke, it is out of stock at Yamaha US online store:<br />http://www.yamahapubs.com/html/itemsearch.jsp?type=OB&Year=1996&model=F50TLHU&x=72&y=11 <br /><br />Rather expensive. Maybe You can get in from some other place.<br /><br />(I assumed it is the F50TLHU model You have, there is a F50TLRU model also of this outboard)
 

Hoggy

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

I’d guess being a realist, that to obtain the Clymer manual is going to be more convenient for me and speedier to obtain. That way I will be able to start tracing the problem on this engine sooner.<br />Would you guys say the Clymer manuals are ok? … the only other manuals that I have managed to come across are Seloc Marine Manuals …. Which would you say out of the two makes of manuals would be best suited to repairing and locating a fault on the cold start system ….. cheers guys!
 

bossee

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

Hi,<br />I had a Suzuki DT65 (2-stroke) before and I bought first the Seloc manual. It cover most things but the electrical wiring diagrams was so bad scanned that I could not read them so I had to buy a Clymer manual also where this was scanned just fine and was readable.<br />I like the Seloc manual little better, at least the manual for Suzuki that I still have (but I have sold that outboard, I use Yamaha F115 now instead). I had also the Service manual for Suzuki DT65 and that was best (I sent it with the outboard when I sold it).
 

Hoggy

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

I am still waiting for this manual too arrive !<br />Tried the other day to start engine from cold, cold as in it was 0 Celsius.<br />The solenoid rods on either solenoids failed to operate, so I manually shifted them myself, basically wondering if it would start this way ... and it didn't, think I might have put the rods into a position that over enriched the mixture or something, anyhow a couple of hours later I tried to start the engine just on the key, touching nothing and it did fire up, so I'm presuming I flooded it .... wish this manual would arrive and soon.<br />Do these Clymer manuals show electrical circuitry by any chance?
 

BillP

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

I bought a carbed Mariner 50hp 4s new in 96 and guessing your electric choke isn't working. The coldest I've started this beast is about 40F-45F. It starts right up at these temps but takes 2-3 minutes to warm up. I see no difference in starting time no matter what the temp. I squeeze the bulb until hard and push the elec choke until it starts, which is 2-3 seconds. <br /><br />Get rid of those NGK plugs and it may start easier. My motor eats a set of NGKs in approx 100 hrs and Champions only get changed when I feel guilty. <br /><br />About the Clymer manual. Mine is #B710 and advertised as "Clymers OFFICIAL SHOP MANUAL". Basically it is the same as most Clymers...some details good and others not so good. This one groups too many engines into the same repair article. Hopefully your motor is the one they show pics and descriptions on.
 

Hoggy

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

I'd guess your more up on outboards than I am, then who isn't.<br />One rule I have followed is always use NGK or Nippon Denso plugs with the jap engines, I have found as an automotive mechanic of 28 years mind, that the jap engine tend to run better with these plugs.<br />I would however use Champion or Bosch plugs with European engines, these tend to be ok, that said so to do the Jap offerings.<br />Most NGK plugs are French manufactured in Europe, Champion being English Manufactured and some Bosch being Indian manufactured as well as Germany!<br />But I'm strictly talking automotive Bill, and in no way challenge your experience/knowledge, it being more than mine, hence I need all the advise possible from you guys!!!<br />Anyhow just hope this manual indicates the wiring colours and their usage.<br />Cheers for your help Bill ;o)
 

rodbolt

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

hello<br /> hahaha patience.<br /> wait for the manual.<br /> you will find the tinest bit of trash or shellac in the carbs will affect cold starts on that motor. you will also find that the choke closing is critical and proper adjustments are imperitive.<br /> keep the NGK's but really on that ign system it doesnt matter.<br /> good luck and keep posting
 

Hoggy

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

Well !<br />I have as some suggested quite rightly, bided my time and waited in anticipation, and the manual has arrived.<br />As was mentioned by some, the manual is to some extent general, but nevertheless a distinct advantage having it.<br />It covers from 9.9hp …. Up too the 100hp Yamaha four-stroke O/B engine.<br />Having looked at the cold start system the 50 hp motor uses, I am still unsure as to just how it fully operates. I understand it functions via a thermal switch, and that when the temp is at a set low level the choke solenoid comes into play.<br />Basically looking at the ” Starboard side of the engine “ there is the choke solenoid and an electrothermal valve, also two thermal switches. This is all straight forward, in the manual it goes into some detail how the function of most of the various models cold start systems operate, but when it comes to this system which incidentally differs from the majority of the other engines this manual covers, it really doesn’t explain it operational function.<br />I’m aware at a given temperature the circuit will bridge bringing in the choke solenoid, its initial feed coming from the ignition switch bridging, this in turn being dependant upon the thermal switch, either #1 or #2 thermal switch “ I will study the circuitry more “!<br />Given that the thermal switch sensed it was at a temperature to function, would I be right in presuming that the choke solenoid operates, if so, is it basically an on off type solenoid, in this I mean its not gradual, whether it be coming on or going off? … ( not like a stepper motor ? ) … would it’s travel depend on the thermal switch resistance even ? … or does it just operate then retract when the resistance value is met? <br />What is the function of the electro thermal valve?<br />Can the choke solenoid be powered up from an outside source, to test it ability to operate without damaging it ?<br />Sorry about the Spanish Inquisition, but I really would like to get to the bottom of this problem that thinking about has probably been with this engine for quite sometime, even prior to me owning it …. Thanks in anticipation …
 

rodbolt

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

dude<br /> let me read your post a few more times so as to de-confuse my poor tired brain. I have been fighting 2001 7.4GsI all day that is so corroded it aint funny.<br /> give me a bit and ill try to splain it all to ya :) <br /> good luck and you study while I fix dinner :)
 

Hoggy

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

Thats some dinner your fix'in rodbolt :D
 

rodbolt

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

hahahaa well I had to wait for my chicken to finnish growing.]<br /> I apologize but I will dig out the manual. can you descripe what your system looks like> not what you read but what it actually has?<br /> good luck and ill try to be back. that 7.4 volvo tried to whup me but I finally got it.
 

Hoggy

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

ello rodbolt ..... sorry for not getting back, but work has been, well a nuisance!<br />Going to have a go at the engine over the weekend, will keep you informed as to how I get on, or not as the case maybe ... cheers M8
 

Hoggy

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

Managed to get round to having a look at the engine today ... tested out feed to solenoid, seemed ok as did the grounding "earth" wiring for the solenoid, watched solenoid function when starting and the plunger "retracted" moving the linkage slightly ... according to the Clymer manual, there is an electro thermal ram, this is a black plastic encased cylindrical devise, which on first impression would appear to be some sort of solenoid? ... it has a plunger, and the plunger seemed to extend as the engine got warmer .... so all in all .. the solenoid operated with the starter motor being cranked, as mentioned the plunger retracting and moving the link, and as the engine warmed the electro thermal ram extended gradually the warmer the engine got.<br />One point I did notice was following the diagrams in the Clymer manual, mentioned two thermal switches, simply referred to as Thermal switch 1 and 2. I'd read into the manual and I'd presumed switch one was for the audible warning feed to the remote, and as it mentioned in the manual switch two was the thermal bridge for activating the choke solenoid, anyhow it turns out there is only one thermal switch on this engine, I look around the engine to the extent I followed the wiring loom and I never found switch 1.<br />When should the choke solenoid operate ? .. is it purely when the starter motor is operating only ?<br />And this devise the japs call an electro thermal ram!.... as mention previously that it extends as the engine warms up, am I right in thinking the enrichment is given when the plunger is in a retracted position, and as it extends it is diminished ?<br />Any help much appreciated ... cheers guys
 

rodbolt

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

hello<br /> yep your on the right track. double check the unloader linkage. make all adjustments with the engine cold. if you use the warm up lever at all it will toss the system in left field. the system is designed to be a turn key only deal<br /> DO NOT use any throttle advance when cold starting.the choke solinoid only works when the engine is cranking<br /> a tap from the lighting coil provides current to heat the electro-thermal plunger.you will need to carefully verify that all fuel bowl levels are correct and no other running or ign problems are present. keep hunting and reading your manual. its a complicated set up that works well if everything is correct and not so well if anything is wrong.<br /> good luck and keep posting
 

Hoggy

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

Cheers rodbolt I will certainly take your advise, just one point before I drive up insane :eek: <br /> <br />Just suppose all was ok with this engine, if I started it up and the system worked fine and the engine fired, what RPM would this engine start initially to run at when cold, I'll say at 32f/0c for instance, basically I'm trying to figure out would it run at a fast rpm till it warms up to normal operating temp then settle down to normal idle speed. ..... cheers m8
 

Cruisin_Along

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

I have a 2 year old 60HP Yamaha four-stroke F60 and I have suffered the same 'cold start' problem. However, it starts immediately with 100% reliability when warm.<br /><br />I have never seen in the owners manual that one should not use the neutral throttle when the engine is cold, but someone did mention that, after pumping the fuel bulb up firm, it helps to advance the main throttle all the way once or twice and return to neutral before attempting to start the engine (presumably allows the fuel to advance closer to the carbs). I tried that but still used the neutral throttle and sometimes flooded the engine.<br /><br />My thanks to rodbolt. Next season I will try cold starts without the neutral throttle (at least until it starts and then I may use it to adjust the idle for desired warm-up).
 

jafa

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Re: Yamaha 50 hp Four Stroke, difficult Starting " Cold "

Hi Hoggy , that electro thermal ram may be similar to the choke device I have on my honda car. Basically its a wax plug that contracts and expands with temp pushing the choke assy round. Incidentally ,mine is water warmed, it has a temp valve installed in line to stop it getting to hot and damaging it. Yours may have something electrically similar with those switches.<br />It also doubles as an excellent service part as the wax will eventually seperate out or leak and then they can sell you a new one.
 
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