1983 Mercruiser 120 Problem

[HSBarker81]

I just bought a 1983 Renken 19ft Open Bow Boat with a 120 Mercruiser I/O. We took it out for the first time yesterday and everything seemed fine. It started right up without a lot of hassle (as i hear a lot about and my girlfriend's father's 140 seems to exhibit), it was a little hesitant on the throttle, but it has sat for a year and a half so the gas may be a little rough and it may just need to be ran a little bit. <br /><br />The problem is this. We were cruising along just below WOT and the motor bogged down considerably. I thought that it was something wrong with the outdrive because it was shaking pretty badly at the rear and when i put the boat in neutral, i could rev the engine fine. I checked the outdrive oil level and it was fine with no water in it. I ran the motor in the yard and put it in gear and it seemed fine other than being a little hesitant coming up still (worse after warmed up). I'm wondering if anyone has ever heard of something similar to this or if anyone has any ideas on what i need to do? <br /><br />Thanks,<br />Harley<br /><br />ps- I have a notion that the prop is too large. It looks like it is about the biggest one you could fit on the boat and at WOT the RPM's were just above 3500...How can I tell what size mine is?

 

[vipzach]

Re: 1983 Mercruiser 120 Problem

I would not worry about the prop size until you are sure the motor/drive are in good order. <br />If the boat sat for a year and a half you could very easily have bad gas. That sounds exactly like what my boat did. Water in the fuel will do that, seem fine in the driveway with no load, under load have little power and low rpm's. I would check your gas filters and replace the fuel water seperator, if you don't have one...get one. Also did you give it any kind of tune-up? New plugs, change oil, check timing, cap and rotor?

 

[HSBarker81]

Re: 1983 Mercruiser 120 Problem

The oil has been changed recently i assume...the filter looks new and the oil has a "new oil" color to it. I have not done a tune up to it yet, but i will do that and change the fuel filters as well. I just took it out yesterday to make sure it didn't take on water or anything. Where is the water fuel seperator? <br /><br />I also topped off the tank (1/4 roughly) with 93 octane gas and now i have put some gas treatment in it...

 

[Don S]

Re: 1983 Mercruiser 120 Problem

Follow the fuel line from the tank to the fuel pump. There should be a fuel filter/water seperator installed in that line.

 

[vipzach]

Re: 1983 Mercruiser 120 Problem

The seperator will look like an oil filter, mine is inline before the fuel pump. If it sat that long without a full tank of gas it more than likely has moisture in it. I put two bottles of HEET in my tank and that helped with the moisture. I would definately get a seperator though if you don't have one. <br /> Also check the plugs and the timing, how does the carb look? It may need rebuilt after sitting.

 

[HSBarker81]

Re: 1983 Mercruiser 120 Problem

ok...i changed the plugs, wires, points, condensor, rotor button, and distributor cap...i gapped the points and plugs as specified. I still need to set the timing, but i need to know what idle speed to set it at...i know that the tag on the motor says 8 deg btdc. What idle speed should i use and will a conventional timing light work for this?<br /><br />As for the water seperator, i don't see one there...i bought a kit but it looks to be hard to install, location-wise and mounting. Can anyone tell me how many fuel filters are on here and where i might find them? That is my next move...and if all of this doesn't fix it, i guess it'll be time to overhaul the carb. How hard is that to do? <br /><br />Thanks,<br />Harley

 

[HSBarker81]

Re: 1983 Mercruiser 120 Problem

bump

 

[olbuddyjack]

Re: 1983 Mercruiser 120 Problem

Set the points with a dwell meter before you set the time. Yes, a conventional timing light is good.<br />I dont know what the recomended idle speed is but around 800 should be good. You want to keep the idle down so the centrifigal advance doesn't kick in while your setting the time.<br />The water separator might be a tough install but its worth it. With out it all the water n such winds up in your carb and you have to tear the carb down to get it out. The filter only stops solids and only some of them. What kind of carb do you have?<br />Its much better explainin this to a dude, a chick would never get it.

 

[HSBarker81]

Re: 1983 Mercruiser 120 Problem

haha... looking online i'm about 95% sure its the rochester r2 (g2?). Its a small 2 barrel and the air filter is held on by a metal clip thing that attaches to the mouth of the carb and then has a threaded stud on top (as oppose to a bolt that goes straight through. I'm going to get the number off it and get the rebuild kit today. <br /><br />Where can I get a dwell meter? <br /><br />Still wondering where the fuel filters are...<br /><br />There is something above the fuel pump that is sealed by pressure from a bolt in the clip above it...i was thinking maybe that was something. <br /><br />On top of this, i'm wondering if my problem of dying down and shaking insanely was something with the outdrive and not the motor...is that possible?<br /><br />Thanks for all the help guys <br /><br />-Harley Barker

 

[Don S]

Re: 1983 Mercruiser 120 Problem

Where can I get a dwell meter? <br />

Any Auto parts store, Sears, just to name a couple.<br /><br />

Still wondering where the fuel filters are...

If you can't find it as I explained earlier, then you probably don't have one, You should install one.<br />There is a filter in the fuel pump, but it's not a water seperator.<br /><br />

There is something above the fuel pump that is sealed by pressure from a bolt in the clip above it...i was thinking maybe that was something.

Yep, that should be a filter.<br /><br />You could also have a plugged up fuel tank vent, or dirty pickup tube in the tank that would cause the same problem.

 

[HSBarker81]

Re: 1983 Mercruiser 120 Problem

where is the fuel tank vent?

 

[HSBarker81]

Re: 1983 Mercruiser 120 Problem

bump

 

[jeff13601]

Re: 1983 Mercruiser 120 Problem

Look on the upper back port side of the boat

 

[HSBarker81]

Re: 1983 Mercruiser 120 Problem

you mean the big vent thing with all the fins?

 

[jeff13601]

Re: 1983 Mercruiser 120 Problem

It should be something that has a small hole in it. If you can see your fuel tank you should be able to see where the vent line goes