1971 Mercruiser inline 6 165hp

[firepro86]

Hey All,
I have an 18ft Tom Sawyer powered by a 165hp inline 6. Ive been having problems with the acceleration. From a dead stop in the water if I pedal to the metal to get a skier up the boat just sputters and dies leaving me with a pissed off skier. I rebuilt the carbuerator, replaced the fuel filter, replaced fuel supply hoses, and the replaced the smallest 15gallon metal tank with a plastic 28gallon tank. Recently I serviced the sterndrive. Im still having the acceleration problem after doing all the replacement and upgrades. Any suggestions? Other that that the boat runs and planes great! It gets up and an easy 35-40mph depending on conditions, its just slow getting going.

 

[Bondo]

Re: 1971 Mercruiser inline 6 165hp

Ayuh,...Sounds like ya covered the fuel delivery side,...

How 'bout the Ignition,..?? Compression,..??

 

[Fordiesel69]

Re: 1971 Mercruiser inline 6 165hp

You still have a problem with the carb acceleration circuit. Check again.

OR, your engine is OVERCOOLING such as a bad tstat or very cool water temps. With proper tstat and 38 degree F inlet water, mine runs like crap as well. Once water is over 50 deg F, it runs fine.

 

[firepro86]

Re: 1971 Mercruiser inline 6 165hp

I just did a compression test and everything pans out with the motor. The starter was replaced last year, and the the coil looks brand new. IM totally stumped. Could it possibly be the distributor points? Under voltage? Im running two big dual pupose batteries and it has a brand new alternator. Maybe theres not enough fuel?

 

[Fordiesel69]

Re: 1971 Mercruiser inline 6 165hp

You still have a problem with the carb acceleration circuit. Check again.

OR, your engine is OVERCOOLING such as a bad tstat or very cool water temps. With proper tstat and 38 degree F inlet water, mine runs like crap as well. Once water is over 50 deg F, it runs fine

 

[firepro86]

Re: 1971 Mercruiser inline 6 165hp

OK, I'll pull the Tstat off and look at it. I never thought an overcooling issue would cause this issue. Hope this doesnt sound dumb, wheres the carb acceleration circuit?

 

[firepro86]

Re: 1971 Mercruiser inline 6 165hp

Alright, so i pulled the tstat off and put it in a hot pot of water(120 degrees according to my laser thermomator) and the tstat opened right up, then i put it in a pot of cold water and it closed right back up. I'm going to repalce it anyways since I already have the part (I was going to replace it this winter when I replace the cooling system hoses). Im going to take it to my local lake and run it to see if this fixes it, thank god i live close to a lake. I'll update later this evening. Anything I should check while I have the boat running on the lake?

 

[ziggy]

Re: 1971 Mercruiser inline 6 165hp

assuming ya got a raw water L6. the tstat is 143*. it's supposed to start opening at 143 and be full open at 163. + 20*F.

have ya laid a tune up on it? like points and condenser, plugs, cap, rotor, then set dwell and then timing?

 

[firepro86]

Re: 1971 Mercruiser inline 6 165hp

I took it in when I bought the boat in April and the mercruiser dealer I took it to said that the motor looked to have just been serviced. It has a lot of new parts under the engine cover. the only things that looks like it hasnt been touched is the distributor. The person I bought the boat from said it had been serviced in Jan. but then he ahd to sell it because his wife passed and he didnt want anything to do with the boat. When I serviced the sterndrive the impeller looked brand new( at which time I felt like a total dumbass because I was repalceing a brand new part).

 

[Fishermark]

Re: 1971 Mercruiser inline 6 165hp

I rebuilt the carbuerator, .......

Sometimes carbs simply cannot be rebuilt - or (no offense) - they aren't rebuilt correctly. Sounds like a carb issue to me. With the engine not running, remove the flame arrestor and look down the throat of the carb while someone moves the shifter into WOT - you should see a healthy squirt of fuel being sprayed into the carb. Check it and see, then report your findings.

 

[firepro86]

Re: 1971 Mercruiser inline 6 165hp

Fishermark: no offense taken, its my first time doing this so i probably screwed it up somehow.

 

[Fishermark]

Re: 1971 Mercruiser inline 6 165hp

Fishermark: no offense taken,

Cool!

I've rebuilt quite a few - and to be honest, sometimes, it just doesn't work. Whether it is a bit of varnish that refuses to come out... or some warping of the body.... or excessive wear in the shaft areas.... whatever it may be. This may not work for you, but if you can find another carb to try, at least you can see if that is the problem or not.

 

[firepro86]

Re: 1971 Mercruiser inline 6 165hp

I shouldve been a mechanic in the coast guard instead of law enforcement..lol

 

[firepro86]

Re: 1971 Mercruiser inline 6 165hp

Alright at the lake.
Fishermark: I looked down the throat while my wife pushed the throttle forward and it looks to be dumping a healthy amount of fuel into the throat, it actually looks like to much to me but we will see.
Ziggy: I replaced the old tstat with a new 145 degree rated one.

 

[firepro86]

Re: 1971 Mercruiser inline 6 165hp

Alright, back from the lake. It didn't stall.but it did sputtered a little and then would dig and it felt like the bow was going to to a backflip, but would then jump up and take off. It's never done the bow high dlgging before. I was able to fix the sputtering by putting a zip tie on a suction hose coming off the carbeurator. Boats running great minus the digging.

 

[Fordiesel69]

Re: 1971 Mercruiser inline 6 165hp

You are producing more power now, so the bow is lifting. Just make sure the outdrive trim is full down.

 

[Oshkosh1]

Re: 1971 Mercruiser inline 6 165hp

In your signature it says: "1971 Tom Sawyer 180 4.3L Inline 6 165hp Mercruiser 1 sterndrive"...

I don't think GM ever made a straight 6, 4.3L. Probably the 250CID(4.1L)/165Hp.

Also...Whilst it's running spray a little carb cleaner around and check for vacuum leaks.

 

[John3]

Re: 1971 Mercruiser inline 6 165hp

Just a thought. I have the same 165 Merc in my Boat. Had a fuel delivery problem, it would start ok & run under load for about 5 minutes and then die. I tried everything (almost). Turned out there was a bit of debris in the fuel line. There is a 90 degree brass fitting where it comes out of the tank & the crud was stuck right in the elbow. It allowed enough fuel to pass to start & idle but was starved under load.
John

 

[Fordiesel69]

Re: 1971 Mercruiser inline 6 165hp

From the sounds of it, he literally replaced the entire fuel system.

 

[firepro86]

Re: 1971 Mercruiser inline 6 165hp

It's definitly an inline 6. It has GM stamped on the block and all of the parts have been GM relpacement parts. I've replaced pretty much everything in the fuel system, from the tank to the supply lines, the fittings, hose clamps, everything. Fordiesel69: if I changed the prop out would that fix the high bow rise? I had it trimmed all the way down it was still digging. I played with the trim up, down in the middle and it still would dig and jump forward and take off.