mercury 25 hp

[rooster1]

just bought a mercury 25 hp this morning at a yard sale he fired it up but it wouldnt idle been setting for a while i went to change the plugs when i got home and there flat i am new at boating but i have never seen one of these do i have to put the same flat plug back it ? and it has a hand control throttle can u get a kit to convert it with cables to the drivers seat paid 550 for it 86 model also i noticed a plate above the propeller about 3 in wide half of it is broke off

 

[KIGuy52]

Re: mercury 25 hp

By "flat plugs" I assume you mean there's no side electrode. It probobly has Thunderbolt ignition so you should replace the plugs with the same kind. The broken plate may cause the prop to cavitate, especially in turns. Depends how bad it is. You should be able to get remote throttle and steering controls.

 

[rooster1]

Re: mercury 25 hp

thanks kiguy what do u mean by cavitate im new at boating i went to to parts store and they had the flat ngk plugs i got a set and a can of seafoam noe in runs perfect now im wondering about the water pump it starts pumping only when i rev it up i would think it starts pumping as soon as it cranks

 

[KIGuy52]

Re: mercury 25 hp

Basically, cavitation is when the prop gets too much air in the stream of water flowing through it when it's pushing the boat. It will cause the prop to "slip" in the water at higher speeds and the engine will rev up, but the boat will slow down. Outboard motors have a flat plate over the prop designed to prevent this. If the plate is broken on your motor it may or may not do that. You'll just have to try it and see.
If the water pump doesn't seem like it's pumping right, you should probobly replace the water pump impeller.

 

[jmburock]

Re: mercury 25 hp

How much was this motor ?? $550. And with a broken off cavitation plate. You might be able to weld on a new one. If a cavitation plate is broken off, I can just imagine the lower unit/ maintenance/ etc. Sounds like you got your work cut out for you. Who sells things for more than $100 at a garage sale?? You must live in an upscale neighborhood?? People give away outboards like this in my neighborhood (coastal Rhode Island).

 

[CatfishingMo]

Re: mercury 25 hp

You may have paid a bit much for the motor in the given condition, but that's beside the point. As for the water pump only pumping when RPM's are high. You should invest another 25 bucks or so and install a new water pump impeller. Sure beats burning up a good powerhead. I'm almost positive that's your problem. You are right it should pump water regardless of idling or Wide open. Since it does pump sometimes that rules out any plugged up line or telltale. Bottom line is put a new impeller in it and have someone that really knows what their doing fix the cavitation plate or your in for a bottomless money pit that will eat up lower unit components.