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671 low rpms only turning 1500 rpms

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KenLeger

New member
I have a 46 Post i purchased last year with twin 671 ti 450s last year both motors turned up full rpms but stbd motor lagged behind and came up slow but did reach full rpms. Over the winter I had the turbo rebuilt and also replaced the injectors. Now motor only turns up 1500 rpms. If i bring the port motor up to full rpms then the stbd will go up to about 1700 rpms. I have re-cheched the rack adjustment several times and also took the cover of the governor and visually inspected and everything seems to be in order. Fuel filters have all been replaced and also has fresh fuel. Intercooler also has been removed and cleaned. In neutral the motor will reach full rpms. Bottom is clean and has fresh paint and also props where checked to and where good.
 
Hi,

What is the fuel pressure at secondary filter? Always good to start with that. Compare stbd. to port readings but should probably be around 60 psi. @ full no-load. (It's been a minute since I was wrenching the 2 strokes.) Hopefully you have the shop manual for specifications reference.

Any black smoke? If there's a boost problem, smoke would be a clue. Still, you may want to gain access and check that the turbo shaft spins freely with no wobble or signs of damage to the wheels. If there are waste gates, check those of course.

Although you said that you've "checked the rack adjustment several times" I don't think it hurts to discuss it a bit to try to figure out what might be causing your problem. A "sticky" fuel rack on one injector will slow the movement of all and could cause it to be "lazy" to reach full fuel or even not at all. You pretty much have to disengage each lever and manipulate each rack with your finger to detect the offender. Considering that you replaced the injectors (attempting to solve this?) it might seem a redundant execise but injectors get dropped all the time.

Hope you ger it figured out.

Good luck.
 
jgmo said:
Hi,

What is the fuel pressure at secondary filter? Always good to start with that. Compare stbd. to port readings but should probably be around 60 psi. @ full no-load. (It's been a minute since I was wrenching the 2 strokes.) Hopefully you have the shop manual for specifications reference.

Any black smoke? If there's a boost problem, smoke would be a clue. Still, you may want to gain access and check that the turbo shaft spins freely with no wobble or signs of damage to the wheels. If there are waste gates, check those of course.

Although you said that you've "checked the rack adjustment several times" I don't think it hurts to discuss it a bit to try to figure out what might be causing your problem. A "sticky" fuel rack on one injector will slow the movement of all and could cause it to be "lazy" to reach full fuel or even not at all. You pretty much have to disengage each lever and manipulate each rack with your finger to detect the offender. Considering that you replaced the injectors (attempting to solve this?) it might seem a redundant execise but injectors get dropped all the time.

Hope you ger it figured out.

Good luck.
Click to expand...

I still have to check fuel pressure that’s my next step. No smoke at all except for when first started get a little white/grey smoke. The turbo was rebuilt and I also did recheck the shaft it spins really smooth and also when you start the motor it spins right away. No black smoke at all either motor. Thanks
 
You've had 2 sets of injectors with the same result. Not likely it's injectors. Check the fuel pressure, if ok, with the engine off, check all the linkage, disconnect as necessary, be sure everything works smoothly. With the engine running and in gear, disconnect the governor and operate the linkage by hand.
 
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