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1981 Mercruiser 165 runs rich HELP

G

gonkystyle

New member
"I have a 1981 mercruiser with

"I have a 1981 mercruiser with an l-6 165hp. It pulls realy well up to 3/4 throttle. But after that it bogs down till I pull it back to 3/4 throttle. Ive lost 10 mph off my top end. I replaced plugs, wires, cap, rotor, points,(had it dwelled and timed)replaced fuel pump, fuel filter, and just rebuilt carb. Soaked the carb for a week in chemtool and blasted every oriface out with carb cleaner. Put back in the water again today and its still bogging out. The fresh plugs are full of black soot again! At this point I have no Idea what it could be and I know its something simple that I havent tried. Please help I need my baby back!!!
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I am not sure how the sooted u

I am not sure how the sooted up plugs would figure into a low float. Might also want to look at the choke and make sure it is all the way open when you are wide open on the throttle. You want to make sure that it is held open by the choke mechanism so it doesn't suck back closed when the air starts rushing down at full throttle.

Eric
 
I did not change the float whe

I did not change the float when I rebuilt the carb. It is the old brass type. It felt light like no gas got in to it. Im thinkin maybe the choke is stickin. Do I dare set it to lean so it stays fully open? That wouldnt hurt nothing would it. Thanx for the posts!!
 
"No I put the jets back in. I

"No I put the jets back in. I was pretty carefull cleaning it out and puting it back together. The thing about all of this it runs 100% better than it ever has by tuning all of this up except at full throttle. I am missing something. If and when we figure it out its going to scoot!!
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Pts. ign.? Look at the advanc

Pts. ign.? Look at the advance weights under the pts. plate. Clean and lube w/WD-40. Make sure they move easily.

Check the choke to be sure it is open all the way. Adjust as needed or replace if worn and tired. Clean or change the plugs.
 
"Choke should be fully open wh

"Choke should be fully open when the engine is warmed up, do you have an electric choke or heated choke ? I like to set it when the engine has sat over night, and I set mine just so it closes lightly."
 
Ok put it back in the water to

Ok put it back in the water today still the same. Choke is fully open and functional. I took the cap off the distributor and the points plate. Cleaned up the wieghts and lubed. Didnt seem to idle right after that so I pulled it apart again wiggled the weights made sure it was all freed up. And it idled fine again. But I still cant get that last 700 rpms out of it. Can the weights wear out? Do you need a different distrib. to go electronic? I have pretty much ruled out the fuel as the problem its got to be in the spark? It all dwelled fime and timed fine? I Dont know. The idle mixture screws on the carb being out of adjustment wouldnt cause this would it? I set them when the boat was in the water to about 700 Idle rpm. Oh ya before I forget the plugs werent sooted up like before but I didnt run it past 3/4 throttle except for the initial try to go past it. Plugs were brown. Thanx for all the help so far!!
 
"The pertronix electronic igni

"The pertronix electronic ignition is 30 minute job to install and that includes timing the engine. Definitely the way to go if you ask me. I still think it sound like you should check the float adjustment. The adjustment on mine was something like 5/8" from the gasket to the seam on the float. I know mine acted the same way and my float was out of wack. Also make sure the needle jet has not loosened up, cause that will cause the same thing as the float level being low.....yes that happened to me too!

Eric...Fellow in-liner."
 
Eric did you measure from the

Eric did you measure from the top of the carb to the float seam? Did you go with a plastic float? Mines still the old brass unit? What year is yours?
 
Also did a compression check.

Also did a compression check.
DRY #1 150 #2 145 #3 145 #4 140 #5 145 #6 140
WET #1 175 #2 160 #3 155 #4 165 #5 170 #6 155
 
"unless he's done a mod &#

"unless he's done a mod (which I'm working on) all inline 6s except the 292, 200hp are 2bbl carbs.

another way to set a float without a ruler is to turn the top of the carb upside down and the float should be parallel with the underside/now top of the carb.

Do the weights were out? well the pivot holes can wear and you might find some new plastic bushings at a "auto speed shop" the springs get worn too.

Idle mixture screws are only for idle 0 to about 1500-1800 RPMS when the power Vavle transitions to the main jets."
 
"Mine has a Rochester 2-Jet.

"Mine has a Rochester 2-Jet. I just looked in the manual and they don't provide carb ajustment data. They said to get the data from the information in the rebuild kit. My carb, if I remember right you turn it upside down and measure from the gasket to the seam on the float. And yes mine is a brass float."
 
"Check the anti-syphon valve;

"Check the anti-syphon valve; they sometimes get hung up and won't let full flow pass. Also make sure the tank vent hose and screen are unobstructed - mud daublers love those things. Last item is make sure the timing advance provides full advance, using a light - don't remember the value but it should be in the manual. Both the weights and the springs will wear and 'jumpy timing' usually results. A burr on any of the friction surfaces will keep it from advancing fully.

You can also plumb in an outboard tank, temporarily, to isolate the issue to fuel or ignition."
 
"Per SELOC: Rochester 2GC for

"Per SELOC: Rochester 2GC for 165 engine

Float level: 21/32", first raise float by hand and let it drop; do not force it.

Float drop: 1-3/4" measure from the air horn w/gasket in place to the bottom of the float.

Pump rod: 15/16""
 
"perhaps your ignition coil is

"perhaps your ignition coil is starting to break down, don't see where it was replaced."
 
"Guy, thanks for the Rochester

"Guy, thanks for the Rochester info, but I think he has a Mercarb. But I will keep the info for me. Was the 21/32 from the gasket to the top of the float or to seam on the float?

Eric"
 
Eric:

Manual doesn't sa

Eric:

Manual doesn't say one way or the other. I would see what the old one measures and compare them. I would expect it to be from the gasket to the seam. It's been 2 years since I did my Mercarb last.
 
Took the advance weights out a

Took the advance weights out and thoroughly cleaned them. Still the same problem. Next Ill set the choke and Ill update.. Thanx for all the help guys!!
 
Any chance you could get/borro

Any chance you could get/borrow another carb and/or distributor and intstall one or the other at different times so you can start eliminating possibilities?

Eric
 
"Set the float it was off by q

"Set the float it was off by quite aways. The kits specs were 1 7/8" from gasket surface to bottom corner of float. Took it back out and it still wont run full throttle.. I'll be checking the gas tank vent and anti-syphon valve today. I wish I had another carb or dist. to rule out. The advance weighs did show some wear on the tips. That will be my next step if all vents check out o.k.
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"if you go run it, take a timi

"if you go run it, take a timin light and see how much total advance the timing experiences. making a little table RPM vs ignition timing (degrees) every 400 rpm +/- would help, too."
 
All vents turned out to be fin

All vents turned out to be fine. Didnt have a timing light with me though. Is it possible there is a valve issue with the engine or some other internal issue? Does the compression test I took look normal for a marine engine?
 
For an old in-line 6 cyl. I th

For an old in-line 6 cyl. I think the comp. numbers are good. Dump 1/2 can of SeaFoam in the oil just in case you have sticking valves.
 
Condencers can short out and k

Condencers can short out and kill ignition or cause a myriad of odd symptoms.
 
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