Logo
FULL SITE MENU

50 hp merc high end failure

S

sportcrabber

New member
"50hp merc 0g332844 Motor is I

"50hp merc 0g332844 Motor is I believe a jap motor probably tohatso built 1996.I lose top end with no at any time .Sometimes after running all day and sometimes from the start. When running properly boat will run 25 to 28 knots, when top end is lost 7 to 11. Carbs have been rebuilt and I went to a remote tank with new fuel line to eliminate the chance of a fuel problem. The fuel lines from the fuel pump to the carbs have not been replaced. Pumping the fuel bulb does not correct the problem while underway.This year the volt reg and stater were replaced and this didnot eliminate the problem.
Help; switchbox ,thermostator possibly fuel pump
any thoughts pr experience out there"
 
"That's a Merc built model

"That's a Merc built model. Powerhead and gears were supplied by Yami, but the ignition and everything else is pure Merc.

You need to determine whether it's the ignition or fuel that is restricting your top end. We can guess all day as to what the possible cause is and you can spend hundreds swapping parts or you can trouble shoot.

A timing light will let you see rather quickly if you are losing spark when the motor is restricted. If the spark is good then you concentrate on the fuel system.

Of course a compression test and possibly a leakdown test should be your first order of business..."
 
"Thanks Graham,
I thought i

"Thanks Graham,
I thought it was possibly a tahatso motor because when I set up remote tank and hoses I had to by a tohatso fuel conector to connect to
the motor. I also had been told it was a slot motor by the service manager where the voltage reg and stater were replaced.
I will have to take it somewhere to get the compression check. Explain a leak down test. Evidence of this happens only when under way
with a load on the motor. I crab mostly with motor running low after setting up. This happens most often after pulling pots for a couple of hours at low speeds. Although it seems to be happening more often."
 
"If it hasn't been done, r

"If it hasn't been done, rebuild your fuel pump. Be sure to get the kit from Merc so you get the upgraded check valves. The problem you are describing can be cause by ethanol. It causes the old rubber check valve to curl up on the edges. The new replacement valves are "plastic".
Merc issued a TSB on this but unfortunately it is no longer available on the web."
 
Rebuilt fuel pump and replaced

Rebuilt fuel pump and replaced rubber check valves Motor ran great in the yard on the hose
Hopefully I can get a sea trial before packing things up Thanks IBNFISHN a great save for under 20 bucks if its succesful
 
Back
Top