1978 Mercury spitting water from plugs...

[4x4dakota]

The motor is a 1978 Merc 402 - 40HP and boggs down at WOT. I've gone thru every thing that should be checked or changed and the only thing I've noticed if I rotate the plugs she will run great as long as I keep it at WOT when I slow down she'll bogg down again.
This is when I noticed that while the motor was running there was a small amount of water dripping from the upper cylinder spark plug (between the plug thread and cylinder thread).

I did open up the small gas/water thing on the side, because I was getting no pee stream and found mud and worms in there blocking the flow of water. See picture below(Black hose is gas, white hose is water). If I bugged up the gasket I imagine this would cause a problem.

Any ideas would be greatly appreciated. I would really like to get this boat going for this weekend at the cottage.

Thanks in advance.

 

[DamianJP]

Re: 1978 Mercury spitting water from plugs...

Hey 4x4dakota

The Bogging could be either fuel delivery or spark. Or abit of both. When did ya do the carb or fuel pump? Check carb when it bogs down, does gas flow out or around the carb? Im not sure how to check your fuel pump.

Mabey this can relate to your engine, was for a 1983 150 black max ***Thanks to Jmartin***
"Quick check. Pull the pulse line off the fuel pump and look inside it. If it's wet, throw in a fuel pump kit, the diaphragm gave up the ghost."



The water by the plug is prolly a water jacket gasket and/or the metal that sandwiches that gasket is pitted and not create a good seal for the gasket. You did mention mud and stuff in water area so it might have pitted up in there.

My friend just did the same job on his 1980 Merc 50HP. Had to pop off the water jacket cover and make sure the cover isnt warped. Then check for pitting on the areas that sandwich the gasket. Then grab a new gasket. If pitting he used JB weld and then lightly sanded it back down to a perfect level again to make up for the pitting so the gasket has backing to create a seal.



Lemme know what you find,
DamianJP

 

[4x4dakota]

Re: 1978 Mercury spitting water from plugs...

Thanks for the reply,
Carb and fuel pump are good.

I don't want to sound dumb, but what and where is the water jacket gasket?

Like I said. In the photo the little thing with the two hoses Black and grey I removed. Can someone tell me what this is called? I'd like to order a new gasket for it.
Correct me if I'm wrong, the black hose feeds fuel in the front of it, and the white hose is water for the cooling system and they are divided by a gasket.

 

[DamianJP]

Re: 1978 Mercury spitting water from plugs...

Hello 4x4

Dont worry about feeling dumb, we all come here to learn, fix stuff, and have fun.

Well if the fuel delivery is good then mabey spark for the bogging down.
Heres a diagram of the fuel pump and filter for a list of gaskets and such.
http://www.crowleymarine.com/mercury-outboard/parts/489_11.cfm
I'm not sure of the function as to the water and fuel there, but I think its just a fuel pump that bigger black thing, the smaller circle one is a filter both just fuel. The fuel pump is going to be a rebuild

Parts


2 Valve kit check
3 Diaphram Kit
4 Not on that web site , Ill look around
5 2 Gaskets Also not on that website, Ill look around
6 Retainer
7 Screw

As for the water jacket its back plate that the plug screw thru.
Your going to be working with 34 and 35 parts and the screws.
http://www.crowleymarine.com/mercury-outboard/parts/489_12.cfm

Im not 100% that is your leak but almost certain.Now with that said some people prefer to try and band aid it with silicone because the pressure should reach more than 6-8 PSI. And for the fact that they are worried about breaking the bolts that hold the jacket on.

Your screws dont look like that motor has seen much or any salt water so I think you will be fine with PBlaster/WD40 if you wanna fix it 100% by replacing the gasket and checking/repairing any pitting your find on the water jacket cover/head.

Type in "leaking from spark plug" in search to see what I mean and to get more info if needed before digging in.



Lemme know what ya think/What ya find,
DamianJP

 

[latin monkey]

Re: 1978 Mercury spitting water from plugs...

that "thing" you're talking about is your fuel pump. if you took it off and found mud and worms in it you should clean it out real good and install new gaskets and also the two check valves in it. take the hoses off and clean them out good too

 

[latin monkey]

Re: 1978 Mercury spitting water from plugs...

and yes the two hoses toward the back are water lines and the two toward the front are fuel lines

 

[4x4dakota]

Re: 1978 Mercury spitting water from plugs...

Hello 4x4

Dont worry about feeling dumb, we all come here to learn, fix stuff, and have fun.

Well if the fuel delivery is good then mabey spark for the bogging down.
Heres a diagram of the fuel pump and filter for a list of gaskets and such.
http://www.crowleymarine.com/mercury-outboard/parts/489_11.cfm
I'm not sure of the function as to the water and fuel there, but I think its just a fuel pump that bigger black thing, the smaller circle one is a filter both just fuel. The fuel pump is going to be a rebuild

Parts


2 Valve kit check
3 Diaphram Kit
4 Not on that web site , Ill look around
5 2 Gaskets Also not on that website, Ill look around
6 Retainer
7 Screw

As for the water jacket its back plate that the plug screw thru.
Your going to be working with 34 and 35 parts and the screws.
http://www.crowleymarine.com/mercury-outboard/parts/489_12.cfm

Im not 100% that is your leak but almost certain.Now with that said some people prefer to try and band aid it with silicone because the pressure should reach more than 6-8 PSI. And for the fact that they are worried about breaking the bolts that hold the jacket on.

Your screws dont look like that motor has seen much or any salt water so I think you will be fine with PBlaster/WD40 if you wanna fix it 100% by replacing the gasket and checking/repairing any pitting your find on the water jacket cover/head.

Type in "leaking from spark plug" in search to see what I mean and to get more info if needed before digging in.



Lemme know what ya think/What ya find,
DamianJP

I changed the gasket kit for the fuel pump, and checked the valves. No changed in the bogging. Althought this week it did not bog as much.

I wasn't able to change the water jacket gasket because they had none in stock, however the mechanic at the marina said that this would not cause any booging unless water was spraying a bad wire. (it's definately not enough water to spray anything).

Also noticed that there is some oily water in the bottom of the cowl.

This is exactly what its doing. at WOT she boogs down and if I leave it there booging every so often I get a burst of power, just for a second and she'll boog again, eventually she gets a burst and just just takes off.

 

[Faztbullet]

Re: 1978 Mercury spitting water from plugs...

From your discription thats a fuel problem in carb either from debris floating around high speed jet to(most likely) fuel level not correct due to sticking inlet needle or misadjusted float....