1975 50 HP Fast,slow,fast,slow, fast,slow...

[dabluflash33]

My motor is running strangely as it will run at a good speed but then it barely moves. Sometimes it will gradually pick up speed over a period of time until it is full speed. Once its up to full speed it will stay there but if I bring the throttle down to neutral and then try to go full throttle again it will either take a few minutes to gain the speed or not at all.


Has new plugs
wires
coils
good spark
good compression. (can't remember # but i believe 150's (Could be wrong but mechanic said i had excellent compression)

A carb problem would be consistant wouldn't it?

 

[krogie]

Re: 1975 50 HP Fast,slow,fast,slow, fast,slow...

it definetly sounds like a fuel issue to me , have you done a carb rebulid or cleaning yet?

 

[dabluflash33]

Re: 1975 50 HP Fast,slow,fast,slow, fast,slow...

No I haven't before i go into rebuilding the carb can I try a cleaning first. What would I use to clean it out?

 

[crxess]

Re: 1975 50 HP Fast,slow,fast,slow, fast,slow...

Have you tried a different tank and hose? could be a fuel draw issue.
Also possible running to rich at idle temporarily fouling plugs. Have you tried leaning out low speed settings?

 

[krogie]

Re: 1975 50 HP Fast,slow,fast,slow, fast,slow...

remove the carbs first, this is the only way to do it right . try not to disturb the linkages when removing . remove the bowl(s) and chek for any blockages on the high speed jet. check and replace the float and needle valve if needed.soak carb in carb cleaner making sure to remove any rubber or plastic parts if any,blow carb out with air making sure to get all passages and the slow speed jet.

 

[tashasdaddy]

Re: 1975 50 HP Fast,slow,fast,slow, fast,slow...

read the Top Secret file, 2nd thread in forum. have you checked compression? are you sure you have constant spark? on both cylinders, really sounds like you have a cylinder coming and going. is the vent open on the fuel tank, it cannot pump fuel out of a vacuum.

 

[dabluflash33]

Re: 1975 50 HP Fast,slow,fast,slow, fast,slow...

The mechanic I took it to said it had good spark and compression. But if it is losing spark what should I look at to correct it? it does have new coils, wires, and plugs.

 

[crxess]

Re: 1975 50 HP Fast,slow,fast,slow, fast,slow...

For some reason it is starting to sound(to me) like a float needle not fully closing. At full throttle the never close due to fuel draw. back at idle the have to open and close constantly.

If one is not fully seating the motor is slowly starting to flood/foul. Once speed(rpm) is attained the plugs start to clear and burn off running correctly again.

Get the RPM's above the problem. Shut motor down and in neutral.
Pull and inspect plugs.
Should be clean and dry.

Run motor at problem RPM's
Repeat above test.

I'd almost bet 1 or both plugs will be wet and stained.

 

[daselbee]

Re: 1975 50 HP Fast,slow,fast,slow, fast,slow...

Spun prop?

 

[dabluflash33]

Re: 1975 50 HP Fast,slow,fast,slow, fast,slow...

what do you mean by spun prop? Stripped gear?

 

[daselbee]

Re: 1975 50 HP Fast,slow,fast,slow, fast,slow...

I could not really tell by your post exactly what was going on. You do not say if the engine is running at normal RPMs, you just say that the boat will not get up to speed.
I think it is a LOOONNNGGG shot but if the prop was spun, or slipping internally at the hub, it may take a long tome for the boat to finally get up to speed.
It all depends on what the engine is doing RPM wise. Is it racing way up, but you have very slow boat acceleration, or is the motor itself at a low RPM and then slowly builds up RPM and the boat then follows in a pick up of speed?

I guess for me I need more clarification of the problem.

 

[daselbee]

Re: 1975 50 HP Fast,slow,fast,slow, fast,slow...

My motor is running strangely as it will run at a good speed but then it barely moves. Sometimes it will gradually pick up speed over a period of time until it is full speed. Once its up to full speed it will stay there but if I bring the throttle down to neutral and then try to go full throttle again it will either take a few minutes to gain the speed or not at all.

I underlined the part I am confused about...what barely moves...what is "it".
The boat or the engine? To me, I read it as the boat barely moves.

 

[dabluflash33]

Re: 1975 50 HP Fast,slow,fast,slow, fast,slow...

The rpm's dont sound like they are at their peak. Though they are noticeably higher than at idle, the boat does not gain much speed. I would say the Rpm's are up but the boat doesnt move very far. When the boat starts gaining speed you can also hear the rpms increasing

 

[daselbee]

Re: 1975 50 HP Fast,slow,fast,slow, fast,slow...

Well, I don't know...I can't get a good picture of what you describe, but I know this....
mark a line, scribe a line across the prop and the prop washer, and the prop nut. Scribe it good.
Then run it. Stop and examine the scribed line. If it has changed; if the scribe is "off", then your prop hub is spun, and you have slippage at the prop.
I doubt it, but,
this is a FREE test....

 

[steelespike]

Re: 1975 50 HP Fast,slow,fast,slow, fast,slow...

It's not a spun hub a spun hub causes the motor to rev and the boat will slow.Once spun 99% of the time motor will just rev when you try to speed up.
If you were losing spark on one cylinderr it would be like turning a switch on and off.Lurching fast and slow about full speed to half speed.
When accelerating try squeezing the primer bulb if it help you may have a fuel pump problem.Or try a little choke if it helps you probably have a dirty carb.99.9% of the time the only way to clean is a rebuild.