Yamaha 50hp, can't get it over 3500rpms

[scott craven]

Best not to Rev the motor on muffs anyway. Too many variables with water pressure.

 

[Fizzishin]

Sea foam not seafood

Ya, I'm going to dump a bottle of seafood in there now and see if I can rustle up some 'hos

 

[Alex_c]

What type of muff do you use? Does water flow to both sides, or just one? I also try not to crank the water open too much since too much pressure thru the muff can cause the pump to cavitate.

https://fortnine.ca/en/kimpex-dual-flow-motor-flusher-745330

 

[Fizzishin]

I had some cheapie CTire muffs, switched to a barrel now though.

Just took it out and it still didn't want to rev past 3900 once it's in the water, though it had no problem doing so in the driveway. Will have to take it in asap

 

[Just fishing]

Best not to Rev the motor on muffs anyway. Too many variables with water

I have no problem anymore , I put a pump in that keeps pressure at 60 psi and a 3000 gallon water tank all filled by my well pump ,I can run my 150 hp for 15 minutes at 2000 rpm cleans out all the salt deposits. I do that at least twice a season and once just before storing for the winter .

 

[Just fishing]

I had some cheapie CTire muffs, switched to a barrel now though.

Just took it out and it still didn't want to rev past 3900 once it's in the water, though it had no problem doing so in the driveway. Will have to take it in asap

Probably needs impeller for water pump changed

 

[scott craven]

It might need an impeller but that wouldn't have anything to do with the rev restricting.

 

[Fizzishin]

It might need an impeller but that wouldn't have anything to do with the rev restricting.

I had the impeller done last year, should be good to go. Will post an update once I figure out what is wrong in case anybody else can use the info

 

[tubber]

These are my experiences with my Merc 50
Did you get any alarms at 3900? (McDonald launch mud/crap blockage)
Was it surging? (Fuel pump -I had to hand squeeze bulb to stay on step to get home- twice)

 

[Fizzishin]

These are my experiences with my Merc 50
Did you get any alarms at 3900? (McDonald launch mud/crap blockage)
Was it surging? (Fuel pump -I had to hand squeeze bulb to stay on step to get home- twice)

Took it out yesterday and no alarms. The alarm only seemed to go off when in the driveway and using muffs. Fuel not surging, normal and steady up to about 3000rpms and then it starts chugging a bit and struggles to 3900rpms where it tops out.

One more thing I will try today is take it out and run it on a portable gas tank with fresh fuel. That will rule out (in my mind at least) bad gas in my boat reservoir....

 

[Max123]

My guess - when you had the fuel lines done, a small piece of debris got into the carb. Replace any in-line fuel filters under the cowl, take the carb off and blow out the jets (i'm assuming old carb motor and not fuel injected).

 

[Just fishing]

It might need an impeller but that wouldn't have anything to do with the rev restricting.

Both of my motors restrict revs when motor is running hotter than it should ,if temp continues to rise a audible alarm comes on .

 

[Fizzishin]

Well it seems like the boat gas is ok.

Changed my spark plugs and will see if that helps.

 

[goatman]

did they use that fuel line with a liner inside it?

 

[bulldog10]

Check the neutral safety switch on the engine. If the little tab doesn't pop out when you shift into gear it puts it in limp mode. Motor will shake and d-rate the revs but seem fine in neutral.

 

[Fizzishin]

Check the neutral safety switch on the engine. If the little tab doesn't pop out when you shift into gear it puts it in limp mode. Motor will shake and d-rate the revs but seem fine in neutral.

Are you able to screenshot a pic of where I can find the switch? I'll google around and see if I can identify it. cheers

did they use that fuel line with a liner inside it?

Not sure, reputable company so they would have used whatever is standard.

 

[bulldog10]

Are you able to screenshot a pic of where I can find the switch? I'll google around and see if I can identify it. cheers

Not sure, reputable company so they would have used whatever is standard.

It's at the start of your shift cable. When in neutral a little tin flap makes contact with a block and lets all cylinders fire but when you shift into gear and pull the cable foward if the tin flap doest spring open and keep contact it drops cylinders and d-rates.

 

[Reel Gone]

I know you said it was serviced but when was the last time the carb was cleaned? Why were the fuel lines changed, just getting brittle or were they coming apart internally? Carb would be my first part to Check if filters are good