RPM Question

[Peter.D]

Question, I am running T225 ox yamaha 2 strokes 1997 original engines, hours unknown, compression 120's and decarbed every year per invoices I received since purchased. After 40 minutes of running @ 3600 rpm in rough seas or swells, the starboard engine will drop to 2000 rpm and the boat will slow and I will push the throttle on that engine up a little and it seems to come back? (does not stall) I first though the cables need adjustment? Then sometimes when leaving the slip the star board engines quits after 5 min pre warm. It starts right up and seems to run rough. I checked the water seperators, fuel pump filter and run ring free and stabil/marine grade in every fill.
What do you think? Overall it runs excellent but every now and then?


I am a new Grady owner(9-12-08, 1997 272 sailfish) and I followed this board for a while before I decided on Grady!!

 

[JUST-IN-TIME]

replace all fuel pumps
cleans the VST stariner
clean the o2 sensor

check TPS voltage

run ringfree or chevron gas with seafoam

 

[seasick]

If this only happens when running in rough seas, that might be a clue. Something might be loose but more likely, something is getting stirred up. There might be gunk in the tank that gets stirred up and sucked into the motor. The engine might also be starved for oil, another high possibility. If the primary oil tank system is not pumping enough, the motor will throttle down as the secondary tank empties. You should have gotten an oil alarm though.
Also check the motor mounted fuel filter ( easy to get to), the thermostats (will need new gaskets even if they are OK) and finally the VST filters ( more complicated to get at)
It would help to determine if the problem is experienced after a certain amount of time, certain amount of bouncing or after reaching a certain temperature.
Sorri I couldn't be more specific but these things can be tough to isolate.

 

[BobP]

Congrats on the Sailfish !

Any alarms going off?

What's the fuel squeeze bulb doing at the exact time the condition occurs?
Is it full or collapsed?

If it's full - hope you got a good Yamaha mechanic in RI, then it's a done deal !

 

[fishingFINattic]

replace all fuel pumps
cleans the VST stariner
clean the o2 sensor

check TPS voltage

run ringfree or chevron gas with seafoam

Right to all the fuel pumps?

Any chance that could be filters?

My HPDI's did exact same thing and it means time to change the VST filter -

I know that these are different motors - so maybe that is the reason.

TIm

 

[JUST-IN-TIME]

they had a problem with the ox fuel pumps
look at them if you see white plastic diaphragms then replace them all

I have 6 pumps i will sell to you at dealers cost, i bought 20 of them and the last job i was heading to the guy sold the boat

 

[grady33]

Had the same thing happen to my YAM 225 2000 2 strokes and I replaced the VST filters and the 3 fule pumps on each engine and presto - everything ran fine afterwards. RPMs on one engine would drop when I hit a wave hard and then come back to life. Not sure if it was the filters or pumps but after replacing both .... problem solved.

 

[Peter.D]

Richie, Fuel pumps?

I have had a few boats in my years and most of them were outboards.
This problem with my starboard engine is sparatic. I have had yamies with water problems and most were from major water and particles in the tank(due to improper placed vent valves) I had no idea there were 3 fuel pumps in each engine???
I own a 1999 150 saltwater series yamaha and had the porpise effect, go over a large swell and loose rmp and get it back when the boat levels back only to have it happen again when you hit another wave.
The problem is It happens when the engine runs for a period of time and I do think there are fuel pump issues somewhere. How much for your 6 fuel pumps? hit me in my pm. Also what is VST, and Oygen filter?
Thanks
Peter

 

[JUST-IN-TIME]

vst
vapor
seperator
tank

 

[gradyfish22]

Since you changed your filters, I'd say it is a pump or you have a blockage and something in a fuel line. You can check your fuel pick up, you can disconnect the fuel line at the tank and there is a pick up tube, there is a mesh screen here, it might have residue on it clogging it. Anither thing to try, when it occurs again, instead of giving it more throttle, try pumping the ball, if it jumps back up in rpm it could be one of your pumps going.

 

[JUST-IN-TIME]

if you run on an aux tank, you can eliminate the tank from the pumps