Older Merc 165 hard to start after a hard run, runs rough, dies

CaptainMak

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Hi, I'm new to this forum as well as boating. So happy I found this forum! Just purchased our first boat for the family a couple of days ago after my kids almost disowned me if I didn't.

Took it on the water today. Started up like a charm, idled nice and smooth at about 600 rpm. Had the kids on a tube, running hard. Ran great for about an hour until we shut it down and went for a swim at a beach.

Then the problem began. After about 15 minutes of being off, the boat started up after about 5 revolutions. Immediately I noticed the idle was rougher than when it was cold. After idling for about 5-7 seconds it shut down. Had to crank it with the throttle about 1/2 open and even then the engine was rough but evened out after I gave it about 3/4 throttle. Ran find after that until, again , we shut it down. Same problem. Rough idle, shuts down in less than 10 seconds unless the throttle is about 1/2 open.

From what I researched on this forum, seems like something to do with hot fuel ?!?! Can anyone confirm this ? Other than this problem, the boat runs 33 mph (not sure how accurate the gauge is) at about 3500 rpm.

Any suggestions greatly appreciated.
 

Bondo

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

Ayuh,.... Welcome Aboard,.... What's the vintage, 'n numbers on yer motor,..??

Is it an I-6, or I-4,..??

Sounds like the carb is leakin' internally...
More throttle at start, helps clear it...

Probably needs rebuildin', or replacin'...
 

CaptainMak

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

What's the vintage, 'n numbers on yer motor,..??

Is it an I-6, or I-4,..??

The motor is a 1977 Inline 6. I think it's a Rochester carb because of the two adjusting screws on the bottom.

Would installing a pressure regulator fix the problem ? Also, kinda smelled like it was running rich when the hot start problems occured.
 

dubs283

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

Would installing a pressure regulator fix the problem ? Also, kinda smelled like it was running rich when the hot start problems occured.

no

upon shutdown, check the carb throats and look for fuel running down into the intake

smells of running rich would indicate a flooding issue, your problem has nothing to do with fuel pressure

rebuild or replace the carb
 

CaptainMak

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

no

upon shutdown, check the carb throats and look for fuel running down into the intake

smells of running rich would indicate a flooding issue, your problem has nothing to do with fuel pressure

rebuild or replace the carb

Just take the arrestor off and look down into the carb while the engine is off ? Sorry for the newbie questions..
 

riptorn

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

Welcome to iboats!
When is the last time it was tuned up? plugs, points, etc. That Chevy inline is hard to kill. Were you watching the temp gauge at the time? Check the gas filter for water. It's on the starboard side of the motor, see through glass bowl.
 

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CaptainMak

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

Welcome to iboats!
When is the last time it was tuned up? plugs, points, etc. That Chevy inline is hard to kill. Were you watching the temp gauge at the time? Check the gas filter for water. It's on the starboard side of the motor, see through glass bowl.

Riptorn, that engine looks IDENTICAL to mine !!! I'll try to locate that gas filter bowl, for some reason I thought the filter was inside the fuel pump sort of like a cartridge-style. As I said before, I just bought the boat a couple of days ago, my first boat and no tune-up has been done as of yet. I know it should be done to keep the motor in top shape.

On a side note, I saw kits that eliminate points and condenser I think, would those be the way to go on these motors to make things a lot easier ?
 

CaptainMak

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

Sorry, forgot to mention. After a hard run, the temp would go up to about 170*-175* but never reached the 180 mark. After starting the motor again, the temp would drop down to about 140*. Seemed like when the motor was the hottest, it was harder to idle without shutting down or idling rough.
 

riptorn

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

Yup, I think you need a tune up. That's a little hot for my comfort. Change the thermostat. As the lakes warm up the hotter your engine will run. Also would you know if the impeller was replaced in the outboard? Don't know to much of the conversion with the points but someone here will let you know. Check your engine oil for water.
 

dubs283

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

Just take the arrestor off and look down into the carb while the engine is off ? Sorry for the newbie questions..

"upon shutdown" - e.g. the engine is running, then you shut it down, when it is off, look down the carb...

Check the gas filter for water. It's on the starboard side of the motor, see through glass bowl.

the glass sight bowl is not a filter, it is a clear glass bowl that allows you to see if fuel is present indicating a fuel pump diaphragm failure

the filter is located in the fuel pump assy
 

riptorn

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

the glass sight bowl is not a filter, it is a clear glass bowl that allows you to see if fuel is present indicating a fuel pump diaphragm failure

the filter is located in the fuel pump assy
Ya I kinda figured that. I always kept an eye on that for water.
 

achris

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

There is a filter inside the fuel pump and another one in the carbie itself. Both need to be checked. If it were mine, I'd install a Merc in-line filter kit with a spin-on filter element....

Do you have the GENUINE manual?

Chris......
 

CaptainMak

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

There is a filter inside the fuel pump and another one in the carbie itself. Both need to be checked. If it were mine, I'd install a Merc in-line filter kit with a spin-on filter element....

Do you have the GENUINE manual?.

I have the genuine manual, but it's a little one, sort of like a basic owner's manual that came with the boat. I'll be looking to get a real one soon. Just have to find the best (read "cheapest") place to get one. :p

Good tip on the filter in the carb. I found the one in the fuel pump and ordered one in. Where exactly is the one in the carb located ? Also, if I DO go with an in-line kit, can I just remove the one in the fuel pump assembly ?
 

achris

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

I have the genuine manual, but it's a little one, sort of like a basic owner's manual that came with the boat. I'll be looking to get a real one soon. Just have to find the best (read "cheapest") place to get one. :p

Good tip on the filter in the carb. I found the one in the fuel pump and ordered one in. Where exactly is the one in the carb located ? Also, if I DO go with an in-line kit, can I just remove the one in the fuel pump assembly ?

Leave the filter in the pump.... Filter in the carbie is immediately behind the fuel inlet coupling....

Give me the year (or better, serial number) of your engine and I'll post a link to a 'cheap' genuine manual... :p
 

CaptainMak

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

Give me the year (or better, serial number) of your engine and I'll post a link to a 'cheap' genuine manual... :p

Year is 1977 Mercruiser 165 (inline 6). The serial number is 460XXX . Can't remember the last 3 digits. Let me know if you need it, I'll get the full # in the a.m. Thanks
 

ziggy

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

he should probably use s/m #2 or #3 and #4 for a '77. likely 2 instead of #32... just a guess though... ;)

best i can come up with is here.
 

achris

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

he should probably use s/m #2 or #3 and #4 for a '77. likely 2 instead of #32... just a guess though... ;)

best i can come up with is here.

OOPS! I looked at his serial number and posted (what I thought) was manual #2..... (Obviously I clicked the wrong link :facepalm:)

try this -> https://docs.google.com/open?id=0B1TAvwZ3TjhfOTI5OTMyZTMtNDNkZi00MDAyLWE5MTYtMTI5N2MyNDM3NjZm

Chris......
Good catch Ziggy, thanks... :redface:
 

CaptainMak

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

ooooooooo..... me like ! :D

Time to roll up them sleeves and get down and dirty.

Thanks a million, Chris !!


How hard is a carb rebuild by the way ? I don't mind rebuilding one if it can be done by a somewhat-capable person.

Also read it might be the low-pressure fuel pump leaking fuel internally. Could this also cause the rough start/idle when warm as the engine could be flooded while it's off ???
 

CaptainMak

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Re: Older Merc 165 hard to start after a hard run, runs rough, dies

???
 
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