1979 Mercury 40hp 2 Cylinder - Help

[crazymanme2]

It wouldn't hurt to rebuild the fuel pump but I don't think that's it because if you pump your primer ball you are like the fuel pump but you say it still needs choke.

I had it one time that a little piece of rubber,from the hose, got behind the needle & seat & would restrict the fuel flow, which would cause a lean condition.


When you take apart a carb take everything apart & blow everything out than make sure each passage is clear by blowing solvent through it.

 

[huntingbronco]

Thanks Craig. On the carb, I just could not figure out how to release the two levers that the float contacts to close/open the needle - so I left it in place. I blasted it with carb cleaner from top and bottom and it seemed to work just fine. Could be the problem, I'll verify using your technique of squeezing the bulb while it is running.

 

[huntingbronco]

Okay - approaching what I consider to be the final challenge for this motor and I definitely need some help/advice/ideas. The front cover has been left off, no doubt being the cause of some of the challenges I have faced in getting this thing running. Anyway, check out the photos and let me know how I can fasten this front cover on so I won't loose it on the road or water.

Front Cover

I am missing the top fastener - don't know what to use - screws don't seem to fit real well.

The lower latch is broken, spring works, but the hook is busted off, so it won't engage the bottom of the cover.

What are your recommendations: replace, remove and reconstruct or just come up with a different mechanism for securely fastening this front cover? Ideas please....

Thanks - HB

 

[crazymanme2]

:idea: How about a little bungee cord.Bend the hook so the end locks into the hole in the cover,pull down tight & find a place to hook or put a little bolt through the hole to give you something to hook onto & pull down. :?:

I might have an old Merc that might have the piece you need,I'll look tomorrow.

 

[huntingbronco]

Thanks Craig - appreciate the idea. Let me know about the parts.

 

[huntingbronco]

I finally got the boat on the water last night. All attention has been focused on getting the boat done.

Now I need some advice on the motor. I had water coming out the pee hole, but the engine got really hot and did not run right. Let describe my observations and maybe you guys have some ideas.

After I rebuilt the carb, I flushed the gas tank and hooked it to the motor. Unfortunately, I think there was still some bad gas in the lines. Anyhow, she fired up, so I thought I would get it on the water and give it a go.

When I squeeze my bulb in the fuel line, it gets firm if not hooked to the engine, however, when hooked to the engine, gas flows through the carb and out the bottom. Bulb does not stay as hard as I am used to.

Engine did not want to run, lots of fussing with throttle position and choke. Once warm, a little choke would kill the engine. We also tried putting a little pressure on the bulb, but it seems like that had the effect of flooding the engine, especially in the end when the engine was very hot.

When it was running, especially after getting warmed up, the motor was making some wicked rattling noises - don't know if that was knock or not... This carb was pretty simple - is it possible something funny is going on in the carb due to the bad fuel getting back into it after the rebuild? Would that cause it to run lean, hot and knock?
Should I just pull the carb, dissassemble, clean and reassmeble? I should not need a new carb kit, should I?

 

[huntingbronco]

Her she sits at the dock - trying to get her to start...

Here's a shot of her running on the water...

After this run, we tinkered for quite a while trying to get her to run right...nothing seemed to work. Man, was she hot when we got to the dock. Read my previous post for more details - need some advice here guys.

 

[gouran01]

just a possibility, if your just wanting tilt/trim to alleviate manually raising/lowering the motor for transport and shallow water and etc, i hooked a small atv winch to my 70hp chrysler and it works frickin great. had back surgery a few years ago and the manual system aint for me

 

[Zum]

Have you done a compression check?
Never like hearing,"running hot"...burn your hand hot?

 

[huntingbronco]

yeah - it was really quite hot, but you could put your hand on the outside. Compression was fine - it was 115-120. For it to get hot with pee coming out, it seems it must be lean? Don't know how else it could be so hot with water flowing.. Even the water in the pee stream was very hot.

 

[gouran01]

didn't read the entire post but possibly thermostat?

 

[huntingbronco]

Thermostat - interesting thought. I eliminated because the water coming out of the engine was very hot. If the THermostat was stuck closed, causing overheating, don't know that it would be so hot coming out. Any other way to check?

Also - I pulled the carb last night. The one item I am not confident about is the float. I did not disturb the levers, but I did change out the float when I rebuilt. The carb was clean. I inspected all jets - none were clogged and the only debris I found was in the filter prior to the carb. So, I don't think my problem was the little bit of bad fuel.

Here is why I am worried about the float. When I squeeze my bulb, with the line disconnected from the motor, it gets firm and stays firm. When I connect to the engine - fuel flows right through the carb and I can't get the bulb to remain firm. I am thinking the float is not coming up and shutting off the inlet valve. Should it be able to resist moderate pressure on the bulb?

This may not be the cause of my other issues, but if this is not right, it too needs to be fixed.

THOUGHTS - Should my bulb stay hard?

 

[Derek]

Have you pulled the lower unit to check the impeller? If the water coming out is hot that is not good. The impeller could be pumping water even with broken vanes, although it wont pump enough to cool the motor. Your last question had me laughing. Yes your bulb should stay hard. Mine gets almost as hard as when disconnected.

 

[wasilvers]

Yes the bulb should stay hard when connected to the carbs. I'm a big fan of adjusting these myself, though it only takes a little bit.

If I read it right, you didn't remove the floats when doing the rebuild? If that's the case, you need to remove them and clean the fuel inlet - carb cleaner and clean rag. The main reasons your bulb doesn't get hard -
float needle is clogged, dirty, your float isn't adjusted right, a float has a hole in it, a fuel line has a hole in it, or your bowl isn't put on right (lowest part of the float bowl goes away from the float hinge) and doesn't allow the float to work right. (been there, done that )

I would start with pulling the carbs and checking the float needles, then making sure the floats hang the same, you can shake it to see if it has a leak. Check the fuel lines (that will cause some of your hard starting and weird running.)

You did mix the gas with oil (sometimes you have to ask the basics).

 

[wasilvers]

Also, your fuel line (and bulb) is hooked up the right way? There is an arrow on the bulb showing the direction of flow. Just some of the basics to check. I saw a boat with the bulb hooked up backwards. Gave the owner a good laugh.

 

[huntingbronco]

wasilvers - I changed the float - just did not remove the levers - they looked right. So the needle and seat that operates by force of the float did not come out - just flushed a great deal. Confident there is no goop in there. Worst case is the prior rebuild put something together wrong - that's what I am looking at now. Yes, fuel has oil and lines are correctly assembled and working properly. No worries, no offense taken - only stupid question is the one not asked.

BTW - does anyone know how compression relates to running hot?

If a cylinder has bad compression - would it not draw enough oil/fuel to lubricate - there fore it would run hot?

Thanks for the education.

 

[wasilvers]

So the needle and seat that operates by force of the float did not come out - just flushed a great deal. Confident there is no goop in there.

Well, when this needle closes, it's what will cause the bulb to get hard and limit the fuel so it doesn't flow out the carbs and likely flood the engine.

As to compression and getting hot, I've not heard of compression affecting cooling (aside from a cracked head on car). You might have some clogged cooling channels, but I'm not quite sure how you'd get them clear. I had an old force that I pulled the power-head on to clear out all the channels, but that's a lot of work. Is the water coming out of the peehole fast - like you can point it in the air it would squirt a good 8ish feet?

Also when you run it, if it's on muffs, don't run the engine real fast.. I've heard that muffs cant get enough water to cool the motor if it's at higher rpms.

Just trying to help - Will

 

[huntingbronco]

Will - thanks. I took it to a shop today and they said not to spend any more money on it. Sad for me, but you have to consider it might just not be worth spending more on it. So, I guess I can start looking for a replacement motor.

I'll make someone a great deal on this one - I just think the powerhead is going to require work that I am not willing to do.

Bummer.

 

[huntinfool]

I don't know that I would give up on it yet. When you squeeze the bulb the fuel should pass through the seat past the needle and into the float bowl. As the fuel rises it will raise the float and that will force the needle into the seat, thereby shutting off the fuel. You did not take the needle out and therefore can not say for sure there is not any trash in there. I have sprayed to check them and did not see any trash, but when pulled out....there was trash. Also I had one that the rubber tip of the needle came off and was sticking in the seat. Another one did not have the rubber tip. So Since you have nothing to lose, take the carb off. Take the float bowl off. With the fuel line attached give the bulb a squeeze. (you should get fuel out of the seat, so be prepared) Then lift the float so the needle is set in the seat. Squeeze the bulb. You should not get any fuel. If you do then that is the problem. You could be forcing extra fuel into the cylinders and that would cause it to run a bit hotter. I am not saying this is the problem, but it is a free test. If all checks out then put it all back together. If not fix what ever problems you have or post up here and let us help you.
Now as for the running hot problem. Again it is free for you to take the lower unit off and check and see if the WP is in correct. I just did one where we put a brand new impeller in and hooked up the water and started the motor and no water. Took the lower unit off and the impeller was trashed. I finally figured out that it had pieces of impeller in the lower part of the lower unit, where the water intake is and those pieces were being sucked up into the new WP and eating up the impeller. Once I got it cleaned out it worked like a champ. Now if you have a thermostat, you could take the therm out and with it on the water or in the tank start it up. If water pours out of the therm housing then the pump is fine. Now the problem is aeither the thermostat or after the thermostat. Heck the thermostat may be stuck part way or even in backwards, although I doubet it if your getting water, but stranger things have happened. Some modle boats have a set of reeds that the wate has to pass through. If they get a build up of calcium they will impeede the flow of water to the cylinders and thus allow it to run hot. I am not familiar with that particular motor, so I do not know how it is designed. Along those same lines there is no guarantee that there is not some other calcium or limescale buildup internally and that is keeping it from running cool. I heard about someone pouring CLR into the thermostat housing and letting it eat out all the buildup. This allowed it to flow water better and cool better. But I have never done it, so I can not give you any more infoi. I think you would have to block off the pee hole and take the LU off and plug the pick up tube....but again I do not know for sure. Just some food for thought. I hate to see you give up, since you finally got it running.

We are still here to try and assist you in getting it running.

 

[wasilvers]

Right, I wouldn't give up. Since it runs, then the electrics are likely good and you just have some mechanical issues to work through. If the deal is good enough, I'd buy the motor. I could use a backup, or resell it, or package it with a boat and have a second tinny! I tore a 1996 40hp down to nothing and put it back together 3 days later. Then tore it down again a week later (to the crankshaft) and put it back together 2 weeks later. There's not all that much to these engines.

If you're replacing it, you have nothing to lose. Worst case, you can still part out the motor when you're done.