Blown up 25hp

AaronG

Petty Officer 1st Class
Joined
Aug 22, 2004
Messages
234
Over the weekend, I picked up a 1998 Yamaha Four Stroke 25 hp outboard. It has power tilt and trim, and remote steering. I got it from a Honda dealer I know for $50. The motor starts right up, but it has what sounds like a rod knock. Otherwise, the motor is in decent shape, the tilt and trim works, it pumps water, ect. <br /><br />Is this thing worth saving? Or is it just better to part it out. I figure I could get at least $1000 for it if I break it up, but I'm tempted to fix it since it seems like the perfect motor to power a little Carolina Skiff. <br /><br />Are these generally good engines? What special tools are involved in getting the powerhead apart?
 

WillyBWright

Fleet Admiral
Joined
Dec 29, 2003
Messages
8,200
Re: Blown up 25hp

See if the noise is coming from the fuel pump. If the pump runs dry of gas, it makes all kinds of noise.
 

AaronG

Petty Officer 1st Class
Joined
Aug 22, 2004
Messages
234
Re: Blown up 25hp

I'll give it another listen, but it definately sounded like the bottom end.
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Blown up 25hp

buy the service manual and take it apart. if the crank and rods are ok it may be worth saving. somewhere along there that powerhead on the F25 was made by mercury for yamaha.
 

AaronG

Petty Officer 1st Class
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Aug 22, 2004
Messages
234
Re: Blown up 25hp

Does this engine use shell type bearings or roller type bearings?
 

ianyoung77

Petty Officer 2nd Class
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Mar 28, 2005
Messages
121
Re: Blown up 25hp

It will have roller bearings. If one is gone then they all probably need replacing. You need specialised presses to do the crank. If it had knocked for any time then you will need new pistons and rebore as well. It is relatively easy to split the block and see what you are up for.
 

Triton II

Commander
Joined
Nov 23, 2004
Messages
2,479
Re: Blown up 25hp

Hmm, most four stroke Yams have shell bearing big ends, but I'm not 100% sure about the F25, so if I'm wrong I apologise. Aaron, I suggest you get the manual - it could help you with your decision.
 

ianyoung77

Petty Officer 2nd Class
Joined
Mar 28, 2005
Messages
121
Re: Blown up 25hp

oops. missed the 4 stroke! yep sleeve. Seems awfully young to lose the bottom end.
 

AaronG

Petty Officer 1st Class
Joined
Aug 22, 2004
Messages
234
Re: Blown up 25hp

It is almost 8 years old. Probably has some time on it. I'll get the powerhead off this month and take it apart this winter.
 
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