1973 Mercruiser 140 HP Planing issues

[beericks]

Last year I lost my distributer drive gear and got a new one through O'Reilly Auto Parts. I have changed the oil and fuel filter this year and both looked fine. My engine will start and idle just fine and will run out to 5000 rpm without a load on it. But as soon as I put a load on it (in gear and put it in the lake) it will not get over 7 mph or over 1200 rpm. Also the last half of the throttle will not increase speed and makes the motor sound like it is getting too much fuel and loading up. Also this may not be related but when I switch from forward to neutral or reverse to neutral it sometimes just dies. I then start it again and it just purrs. I am at a loss here and need some major help. The nearest lake is 45 miles away and am tired of messing with this thing. I am leaning towards the mechanical advance not working on the distributer but I dunno. Thankyou

 

[Don S]

Re: 1973 Mercruiser 140 HP Planing issues

Did you by any chance change points and have a strange C shaped spring left over?

 

[beericks]

Re: 1973 Mercruiser 140 HP Planing issues

I changed the points and condenser but that was a while ago and it ran fine then. There is a screw for the points and a holding bracket for the condenser but the only springs I see are below that in the mechanical advance. My shop manual also only lists the 2 springs that are for the advance. Where would this spring go? This is what I see in my manual

http://www.boats.net/parts/search/M...7668/DISTRIBUTOR ASSEMBLY AND COIL/parts.html

 

[fishrdan]

Re: 1973 Mercruiser 140 HP Planing issues

Advance springs are under the points plate, remove the cap/rotor, then 2 screws holding the points plate down, lift the points plate out of the distributor. Check to make sure the weights move out and return under spring pressure. Clean and lube the weights while you are in there. There should be a spring connected to each weight, make sure they are there and not rusted to pieces, a bit of rust is expected after almost 40 years though.

With dying while shifting into/out of gear I'd suspect a bad lower shift cable or possibly a sticky shift arm.

Are you running the boat at high altitude? If yes, what pitch prop? (I don't think it's your problem, just asking.)

 

[dubs283]

Re: 1973 Mercruiser 140 HP Planing issues

Where would this spring go?

i believe the spring clip don is refferring to is the e-clip that goes on the distributor shaft that holds the distributor base plate assy on

its shaped like a '"C" but wider at the ends

some people call them #$%@ clips because when you remove them its, "oh, @#$% where did that clip go?"

 

[beericks]

Re: 1973 Mercruiser 140 HP Planing issues

My distributor plate is held on by screws....note the above link to what my distributor looks like. The weights are in good condition and are not rusted. What type of oil/lube should I use though? Also would a timing issue be my problem? Because since I replaced the drive gear my boat hasn't ran right. I do not have a timing light and just go by what sounds the best.

 

[Don S]

Re: 1973 Mercruiser 140 HP Planing issues

i believe the spring clip don is refferring to is the e-clip that goes on the distributor shaft that holds the distributor base plate assy on

No, I'm not referring to an E clip. I am referring to the spring that closes the points, in some point sets, the spring is separate and has to be put in place next to the copper strip.

 

[dubs283]

Re: 1973 Mercruiser 140 HP Planing issues

if you have no timing light you may as well just guess as to what is causing your problem

get a timing light and make sure the timing is advancing when you are increasing RPM

use 25W-40 oil in your engine, otherwise SAE 30

 

[dubs283]

Re: 1973 Mercruiser 140 HP Planing issues

I am referring to the spring that closes the points

gotcha

 

[fishrdan]

Re: 1973 Mercruiser 140 HP Planing issues

Also would a timing issue be my problem? Because since I replaced the drive gear my boat hasn't ran right. I do not have a timing light and just go by what sounds the best.

You NEED a timing light and a dwell meter if you are working on a points distributor. If not, you are just guessing as the adjustments.

Adjusting the timing to "what sounds best" could burn a hole in a piston or cause valve problems...

 

[beericks]

Re: 1973 Mercruiser 140 HP Planing issues

well guys I took my boat to a dealership and they told me that my timing was way off. They timed it to specs and said take it out and if it is still giving you problems come back and it will need extensive carb work. Although it ran a little better (i.e. 1400 rpm full throttle and 7.2 mph max speed) it still did not get on plane. I would appreciate any ideas you guys have because the second visit to the mechanic sounds expensive

 

[dubs283]

Re: 1973 Mercruiser 140 HP Planing issues

seeing as how the mechanic got the ignition timing set for ya, which is a pretty straightforward task, are you ready to start looking at the fuel system??

 

[beericks]

Re: 1973 Mercruiser 140 HP Planing issues

yeah I am I have changed the fuel filter already and looked at the carb and took it all apart and it was mostly clean.

 

[dubs283]

Re: 1973 Mercruiser 140 HP Planing issues

here is a list of things to investigate:

http://forums.iboats.com/showthread.php?t=295070

 

[beericks]

Re: 1973 Mercruiser 140 HP Planing issues

would a restriction in the exhaust cause lack of power under a load situation but not when the motor is in neutral? Also what about a stretched timing chain. This planing issue occured when I stripped out my distributer drive gear on full plane and hasnt ran right since.

 

[dubs283]

Re: 1973 Mercruiser 140 HP Planing issues

would a restriction in the exhaust cause lack of power under a load situation but not when the motor is in neutral?

yes

there is no timing chain on your engine

the camshaft is gear driven

 

[beericks]

Re: 1973 Mercruiser 140 HP Planing issues

oh well thats a good thing about the timing chain. So how would one check for an obstruction???

 

[dubs283]

Re: 1973 Mercruiser 140 HP Planing issues

how would one check for an obstruction???

best way would be to pull the drive, check the exhaust bellows and look into the y-pipe

also, examine the exhaust passage in the drive

 

[beericks]

Re: 1973 Mercruiser 140 HP Planing issues

I got a carb kit today and was wondering if part of my problem might be a bad accelerator pump. I will put the new one in just in case. I do remember a couple of years ago that my boat was sluggish getting out of the hole but over time did get better. Since my boat did not see any water in the last two years, and I did not put Sta-Bil in it, I was thinking that maybe my accelerator pump filled full of varnish. Might this be the culprit? I blew out all of the passages and everthing looked fine. We did tear the gasket that was on the venturi cluster while inspecting that...hence the carb kit. We took apart the carb because of the idle mixture needles when seated all the way in did not kill the engine.

 

[beericks]

Re: 1973 Mercruiser 140 HP Planing issues

Ok so I finally figured out my problem and it turned out to be very simple. So dont take the easy steps for granted people and learn from my mistake. I had the firing order messed up instead of 1-3-4-2 I had it set at 1-3-2-4. It works great now