not sure whats goin on with my 74 115 merc

[switzer115]

OK so heres my prob i bought a 1974 switzer ski/speed boat i was told it ran fine and heard it run when i take it out i have major probs thenum 6cyl spark plug keeps backin out and water comes out all around were the plug screws into will someone please tell me what is goin on and how i can fix it also boat runs great at 3/4 throttle but when u full throttle it runs untilll alll the gas is gone outa bubble and then falls on its face but if u pump the bubble it will continu to run i have replaced the buble twice and andthe fuel lins someone please help me im in dyer need anything will be helpful and greatly appreciated

 

[AMD Rules]

Re: not sure whats goin on with my 74 115 merc

Try a new spark plug. Most likely the plug gasket is shot on it allowing it to be backed out. Surely you could torque it down more, but you risk stripping the threads. New plugs don't need as much torque as old plugs, to keep them seated.

Your water leak is not related to the spark plug issue, and is a result of your water jacket cover gasket leaking. Proper fix is to remove the whole cover plate and replace the gasket (not uncommon). Good idea to check the cover plate for flatness before re-installing. Temporary fix would be to remove the spark plug, and carefully put some sealant around the edge of the cover plate, then re-install spark plug. This might get you through a season. A small leak is not an issue, but it does have a tendency to cool the spark plug which may rest in poor firing.

If your motor is sucking the primer bulb dry and you've replaced the bulb and the lines, you have a restriction in the tank. Make sure you have then vent on the tank open. There will be a small screen on the fuel pickup tube in the tank. Yours is likely clogged with debris.

Good luck.

 

[switzer115]

Re: not sure whats goin on with my 74 115 merc

ok so the info u gave me was great but i decided to pull the cover off and replace the gasket but thats theleast of my probs now when i got the cover off i had a suprise waitin on me the num 6 cyl was busted off the dome part were the plug screws in and am curious how this happened any idea

 

[AMD Rules]

Re: not sure whats goin on with my 74 115 merc

Ouch. That's not good news. I'm not sure what causes a cylinder dome to fracture.

Did it have the proper spark plug in it?

Would be curious to see a pic.

 

[switzer115]

Re: not sure whats goin on with my 74 115 merc

yeah i called and check to make sure i had the right plug and i do yeah it stumps me its almost perfect fracture do u think if i weld it that it would hold compression i will try and get some pics on here

 

[AMD Rules]

Re: not sure whats goin on with my 74 115 merc

I hate to say it, but by your description I would not expect that to be repairable. High compression region and that's a cast aluminum part, and then you'd need to re-machine the landing for the water jacket cover plate gasket. That said, I'm not a certified welder or a certified mechanic. Let's see a pic or two and hear what others have to say.

 

[cannonford57]

Re: not sure whats goin on with my 74 115 merc

the older 65 and 70 3 cyl mercs were bad about the same thing,,,,usually #1 .overheating issues if i had to guess..hope it helps

 

[switzer115]

Re: not sure whats goin on with my 74 115 merc

ok guys all you have said has helped alot but im stumped i fixed my head pob bt know i have another issue when i start the motor at my house it fires up and runs fine push the fast idle up and it idles up but when i take it to the water its starts fine but when i push the fast idle up the motor wont idle up like it does outa the water its like its lackin power somehow and i dont understand how and why when it does fine outa the water what the heck could be my prob im kinda staring to get discouaged any info would be appreciatedand i still havent fixed my gas prob i have rplace everythg from the tankto where it goes into th motor i jstdont undrstand and the bubble stil goes flat

 

[AMD Rules]

Re: not sure whats goin on with my 74 115 merc

ok guys all you have said has helped alot but im stumped i fixed my head pob bt know i have another issue when i start the motor at my house it fires up and runs fine push the fast idle up and it idles up but when i take it to the water its starts fine but when i push the fast idle up the motor wont idle up like it does outa the water its like its lackin power somehow and i dont understand how and why when it does fine outa the water what the heck could be my prob im kinda staring to get discouaged any info would be appreciatedand i still havent fixed my gas prob i have rplace everythg from the tankto where it goes into th motor i jstdont undrstand and the bubble stil goes flat

You fixed a hole in your cylinder? Yes?

Did you replace the fuel tank itself? If not, take apart the fuel pickup tube in the tank...look on the end for the filter/screen. Might be clogged.

Sounds like maybe it starving for fuel.

 

[switzer115]

Re: not sure whats goin on with my 74 115 merc

yeah i have replaced everything fom the tank up bt if it was starving for fuel wolnt itdo it all the time not just on the lake

 

[daveswaves]

Re: not sure whats goin on with my 74 115 merc

AMD rules is trying to help ya buddy, you have a blockage in your tank. To prove it to yourself run the engine on a portable tank. The other issues you have with running differently on land vs water is simply there is no load on the engine on land, there is on water. Your "repair" on the cracked block will not stand the test of time.