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Classic Fifty help

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sportsmanphil

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"Hello everyone. Newby here.

"Hello everyone. Newby here.

I have an issue with my outboard and I am getting kinda thin on ideas (and hair now)

A little background. I bought this boat last fall from a friend. Just before I bought it it was tuned and carbs were rebuilt by a boat repair facility.

I take the boat out and it runs perfect 80% of the time. At random it would stumble at idle and refuse to run. When this happens I have to crank it with the fast idle lifted, push it down and throw it in gear.

Then at random times it wouldnt run top end. I would push it into forward and it would bog but run and slowly get itself to speed. Once at speed it ran perfectly.

A guy told me to check the inlet needles. If it had black tips it was junk and to find factory inlet needles that are all silver. I pull the needles and they were black. I buy factory inlet needles and put the carbs back together. At that time I find one of the floats were slightly out of range. I adjust that and get the carbs back on.

Last night I hook the muffs up, prime the bulb and crank it up. It ran high for about 20 seconds and calmed down to base idle and then it started to die out again. I gave it a bit of fast idle to let the engine warm up a bit and ease it back down a minute later and it refuses to idle.

Funny thing is I will take it out on the lake in a day or two and it will run perfectly, or may not.

The bulb stays tight. New gas tank, new fuel hose.

I might be forgetting some things but the fuel pump was rebuilt too.

This is a 1989 Mercury 45 (classic fifty)

Any ideas would be greatly appreciated."
 
"It really does sound like a f

"It really does sound like a fuel issue, but let's assume that the rebuild of carbs/fuel pump are fine. But I would check/replace any fuel filters (factory or add on's) just incase you have a clog.

Have you checked the compression? if it's good I would head down to Merc and pick up a spray can of "powertune" (cost about 5 bucks). Follow the directions on the can.

That will clean carbon and all other kinds of "cooties" out of the cylinders and ports. You know it's working if gunk that resembles McDonalds chocolate milkshake starts coming out of the exhaust.

If your issue remains after that, at least we know the compression is good and (system) is clean.

That will lead to the next round of troubleshooting..."
 
"I have completed a compressio

"I have completed a compression test and it is within specs as per the book.

What gets me (and ticks me off) is its random. I am not willing to start adjusting the carbs yet as it will run perfect most of the time.

Is there any electronic component that controls the timing?

When I replaced the inlet needles yesterday the carbs appeared clean and clear of any debris. When the carbs were rebuilt last fall, a new gas tank and fuel lines were installed. Since then its had around 35 gallons of fuel ran through.

Thanks for any insight."
 
"1. Adjust the idle correctly.

"1. Adjust the idle correctly. Half of your problem is here.

2. Adjust the throttle linkage so the carbs open LATER than the advance. I suspect the carbs are opening too soon, and that causes all kinds of bogging and stumbling.

Jeff

PS: I can assist you in setting the idle. Just ask."
 
"I would like to agree with ad

"I would like to agree with adjusting the idle but 80% of the time it idles perfect. Actually 80% of the time the engine runs perfect from idle to top end. The issue I am having is random. I can go fishing and it will run perfect, then all of a sudden I will crank it and it dont want to run. Or crank it and run across the water and as I ease off the throttle it dies as it gets close to idle or trolling speed.

But then again, it might not do it for a week.

Im afraid that if I start adjusting the carbs I will hide a intermetent problem making it worse.

If it would do this 100% of the time I would be in better condition to figure out whats the problem."
 
You may be on to it there Jeff

You may be on to it there Jeff - even a bad trigger can cause a "phantom" problem that is touch to track down.

It does sound like you have flogged the fuel system to death so maybe time to grab the timing light and run her normally with the "hood" off and check if it's losing spark when she stumbles....
 
"Thanks for letting me pick yo

"Thanks for letting me pick your brains.

Last weekend it ran great and then all of a sudden as I eased off the throttle it stumbled and died. I tried to recrank and it just turned over, not even a hint of firing up. I have to lift the fast idle to crank the engine when this happens.

I pulled the hood and pulled each plug wire (one at a time) and it threw a 1 inch blue spark and knocked the wee out of me.

I have extensive auto tech history (from GM Pro shop to Rolls Royce/Bentley) Tech wise I am capable. However I have no experience on OB's and know how important time spent spinning wrenches on them can be (which is why I am here, looking for the pros)


IMO, its fuel related. However from my inspections, testing and reviewing of the shop manual I find nothing wrong or out of adjustment.

I have a few more things to try with the carbs (nothing evasive) but my understanding of the timing on an OB isnt great.

The book states to place the throttle at idle in forward. I assume that is to load the engine in gear but no additional throttle.

Please keep the ideas coming and thanks again for helping me out."
 
"Carry a spray bottle of gas w

"Carry a spray bottle of gas with you and, the next time it does this, shoot some into the carb. If that helps immediately, there's your problem.

Rolls Royce and Bentleys! Sheesh. I'm humbled.

Jeff

PS: Guess who was the first aviation causualty in British aviation history? Charles Rolls, killed in the crash of a Wright biplane."
 
"If I'm reading you correc

"If I'm reading you correctly, you were running along fine and when you throttled down it died out and wouldn't start again?

If I have that correct that sounds like a stuck float valve.

When you throttled down, the needle valve that the float operates didn't re-seat itself due to bad float or the needle valve is shot, or crud in the venturi etc - whatever the reason (all in the carb) caused gas to continue to flow completely flooding out the engine.

That would be my number 1 guess (based on some first hand experience - exactly that scenario happened to me the year before last)
"
 
"Here is an update.

Last we

"Here is an update.

Last week I replaced the inlet needles from the black tiped ones to the factory (all silver) ones. The carbs were clean as could be (rebuilt last fall along with the fuel pump, new gas lines and a new gas tank)

When installing the new inlet needles, I had to adjust one flat (only a tad bit) The floats are plastic and not logged with fuel.

*******

Today I hit the lake. Ran 100% (again) I came under a bridge and a fellow boater wanted to know if I had caught anything. I cut the motor, talked to him for a few minutes. I turned the motor back on, eased into the throttle and it started to climb and pull hard like its supposed to and just as it has been doing all morning.

ALL OF A SUDDEN.....its hits about 4k+ RPM and then lost all power and dropped the RPM's to 2k. I pull back on the throttle and it idles perfect (opposite of the problem last weekend) I ease the throttle back forward, good up and just past 2k rpm and then no power. I check the bulb and its firm. I give it a little squeeze anyway and no change.

I throw the timing light on the engine. I crank the engine and engage it in forward. It read around 3 as far as I could tell in the sunlight.

I pulled it home and tested the rectifier (all checked good) I checked the stator all but one test was good. The resistance between the red and red/white wire is supposed to be between 50 - 70 ohm but it read 154. (im going to let it cool and test it again to see if it falls in range)

I also noted that all morning my volt meter on the dash was around 16volts but I noted that after it died out it was around 13 volts. This may have to do with the fact that the engine was at idle. Im sure it was running full throttle when I noticed the 17v earlier.

???? gurrr. Im wanting to hit a huge lake in VA in a few weeks but cannot take an unreliable boat with me."
 
"This is to supplement the abo

"This is to supplement the above post.

I gave it an hour and a half and checked the red and red/white wire on the stator again. The earlier reading was 154 and it dropped to 143.

Could a bad stator cause a bad idle one day and a loss of top end power the next?

I also pulled the 4 plugs and found them to be in good shape, clean with just a touch of oil/fuel. The bottom plug had the most but was still good and clean."
 
Check what the low speed are s

Check what the low speed are set to if they are any less than 1 and a 1/2 turns out you will have a problem so you have nothing to lose by checking
 
"Philip, to your question abou

"Philip, to your question about the stator - I would say quite "unlikely".

Your model (like many Mercs) has both high and low speed windings in the stator, plus the charge coils. So it's kinda 3 independant parts all put together, doing their own job separately.

While it's possible and somewhat common to lose either the high OR low windings, the odds of both of them developing an intermittent issue at the same time is quite un-likely.

I really would look elsewhere...."
 
"I just called Mercury, gave t

"I just called Mercury, gave them my serial # and asked for any TSB's or anything.

She told me that there was 1 that described exactly what I am having go wrong. She said that its called "fuel starvation" and the vacuum should be 2.5 inches of mercury on the pulse side.

I asked for a copy but she said she couldnt send me one.

Anyone here familiar with this "fuel starvation" TSB or have access to them?

I am going to install a T fitting in the vac side of the fuel pump and install a vac gauge to monitor this.

If anyone has access to Mercury TSB's that could shoot me a copy of this I would greatly appreciate this!

Phil"
 
You didn't by chance get t

You didn't by chance get the TSB number. I have a pile of them but of course not sorted or cataloged - even the year of the bulletin and I may be able to help out...
 
"She wouldnt give me the TSB #

"She wouldnt give me the TSB # or send me a copy, said it was against their policy because I am not a authorized Mercury repair man.

She entered my serial# and said it was the first on the list. Said the issues I described fit the TSB perfectly.

She did say it was labeled 'fuel starvation'

If it helps, my serial# is OB394249"
 
"It would have took me forever

"It would have took me forever to dig that out. Mine start back in 1976 and I only have them saved by year/number - when I really retire will have to go through them one by one and tack a description onto the file name.

If this is your issue, since you have already replaced the fuel line/tank, a 20 dollar fuel pump kit from Merc would address all the other possible issues listed in that TSB."
 
"I have STACKS of TSB's fr

"I have STACKS of TSB's from Chrysler, GM, Toyota and Nissan. My wife thinks Im nuts for keeping them but I tell her, if its in my man cave, its none ya business ;-)


I have a quick question on my OB. I have the square fuel pump on the front of the block but the dual carbs have "integral fuel pumps" also. So my question is why the engine needs not only the fuel pump on the block but also have two on the carbs. Also what/how do the integrated fuel pumps on the carbs work/powered?"
 
im haveing the same problem im

im haveing the same problem im replaceing the fuel filter and im hopeing its not the diaphram thing.It does seem like a fuel problem with mine it bogs down like you decribe then if you let it set for 10 min or less it runs fine. It seems like a "vapor lock" on a car. The odd thing is on mine it does not have this problem when the propeller is not engaged the engine tacs out. That seemed strange to me when it did it yesterday.I was running along and it started dieing out. When I finally lagged along to the boat ramp and hoped out i cut it off. Went back started it after i pulled my trailer in the water and boom fired up took off 100% like nothing happened. I suspect some kind of fuel problem as you do. I have done everything else you could think of full over haul almost except the fuel pump havent checked the pressure. I'm wondering if that is my problem also let me know if you get it working I'll do the same. I do not believe its a carbaration problem since I had a shop check IT out last year and it ran fine the whole season. They are a pretty good shop and do good work. Keep me posted I'm gonna try and test fuel pressure. I know its not on the inlet side so I'm thinking more as i write this that that diaphram is the culprut. good luck. let us know if you get it worked out
 
"I refused to adjust the carbs

"I refused to adjust the carbs when it ran perfect 80% of the time. The only thing automotive wise that was intermentent with a carb were stuck floats, and the floats in my OB are perfect.

It appears that the fuel has damaged my valves in the fuel pump. Mine was like yours a few weeks ago but has gotten worse. Yesterday I was down to hardly an idle and no top end (thats a first)

I am going to locate one of the revised fuel pump kits in the morning.

****

Anyone have any input on my question above; fuel pump plus the integrated pumps on the carbs?"
 
timing on a 2 stroke OB is a m

timing on a 2 stroke OB is a multi step process.
the spark arm will advance 2-4 degeres before the priamary throttle opens to the off idle position. than the throttle stays there until the spark arm maxes out and than the secondary throttle opens. to the S-cam split and arm is made to do this in several steps.
 
ThE fuel pump is checked for v

ThE fuel pump is checked for vacuum pull not pressure. If you get gas out of the tank first you wont have any pressure. 2-3" is normal
 
"I have ordered the revised fu

"I have ordered the revised fuel pump as per the TSB. The vac was a little low, not too much but lower than the minimal listed.

I hope this fixes the issue."
 
"HEY HEY guys!!!

Now I ha

"HEY HEY guys!!!

Now I have not tested it yet but I wanted to update everyone.

I got the revised fuel pump today. I tore the old one apart (only 6 months since last rebuild), cleaned it up and installed the new components.

When I tore the old one apart, it had about a teaspoon of rubber like dust sitting inside and all in the two check valves.

Differences in the revised pump: The old valves were plastic with a rubber face. The new valves are only a piece of plastic. The retainers are also larger which required me to drill the fuel pump body retainer hole to .125"

Also. There are two spring valves that push on the diaphram, one was missing when I opened it up.


I will be testing on Sunday so wish me some luck."
 
"Good lord man it never ends.

"Good lord man it never ends.

I got the fuel pump installed and took it for a test ride today......worked better but not 100% either.............

Found the fuel hose between the quick release and the fuel pump had become kinked, evidently from when I worked the fuel pump back on.

I left the lake and came home kinda ticked. Started digging and found the line kinked almost shut.........

All I wanna do is have a friggin day of fishing
angry.gif
"
 
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