Rpm

yamprop

Recruit
Joined
Jun 13, 2009
Messages
2
Hi can anyone help me with some troubleshooting on my yamaha 150 two stroke.I am unable to obtain more than 4600 rpm out of the engine. I have had the engine serviced , carbs and jets cleaned .All cylinders are firing as the pots are hot .New rako fuel filter installed , and am runing the engine off a seperat caddy tank , water free.The prop is the same prop used when the engine obtained 5800 rpm before.My maintinance facility say i might have water in the hull , but with two men on the boat ( 19.5 foot) it gets on the plane at 2400 rpm , so i have my doubts about that.When i power up the engine is running smoothe , i obtain 4600 rpm wit 3/4 throttle but when i move to full throttle the engine sits at 4600 rpm.Any help would be appreciated.
 

cousinabe

Senior Chief Petty Officer
Joined
Nov 13, 2001
Messages
765
Re: Rpm

post the full model number so we know what we are dealing with... can only help with what we are reading.

was it a gradual loss of rpms over time or all of a sudden one day?
has a link and synch been performed?
are orange spark plug caps in spec?
has the TPS been checked and adjusted?
 

yamprop

Recruit
Joined
Jun 13, 2009
Messages
2
Re: Rpm

Hi cousinabe.Thanks for the reply.Im not to sure of the model no , but it ia as 150 twostroke , about ten years old.It was a sudden loss of rpm and not gradual.There is full travel onthe carbs , and the plug caps are not a problem.I have however been told that genuine yamaha plugs could make a difference.Please advise on a TPC check.Thank you for your help.yamprop.
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Rpm

we dont even know if you HAVE a TPS.
10 years ago there were about 7 150 HP yamahas and some used different fuel and ign systems.
we can ID it with a full model number.
 

Home Cookin'

Fleet Admiral
Joined
May 26, 2009
Messages
9,715
Re: Rpm

not meaning to hijack but I was getting ready to post a similar question so if you don't mind, two birds/one stone:
2003 Yam 150TXRB 2 stroke carb.
Yesterday ran for first time in 10 days. A little funky on starting as usual. ran great at its sweet spot at 4000. Decided to open up for a burn off. First time, no response, as if the throttle were disconnected. backed down, went back up to 4000, then to full: this time the engine made a slow climb to about 4900 and speed up to around 35 (have achieved top of 48 mph @ c. 5400, same load). Adjusted trim tabs and motor trim to find top end, no real help. If I hadn't seen better #s I'd say it was underpropped.
Also got some rattling from the engine but it didn't feel l ike it was missing.
new fuel, stabilized with a seperator. New plugs <30 hrs ago by dealer service.
To distill: unresponsive to throttle above 4000, slow climb, not achieving top end. Rattling. New problem.
thanks!
 
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