about half the time it runs just fine, idles normally and throttles up normally. the other half i have this problem.

it will idle very rough with lower rpms than normal idle. its a bouncing idle, as if it were missing. if i leave it idling and put it back and forth from in gear to neutral two or three times, it will start idling normally again and i can take off. if i give it gas in gear when the rough idle problem is there it only gets up to about 1600 rpms. if i give it gas in neutral while the idling problem is there it will either die or slowly rev up to about 2k rpms and then burst through to 4000-5000 rpms.


the problem is there hot or cold. ive checked the spark plugs, they are clean. i'm running fresh gas.

any suggestions before i take it in to the shop?

Check your fuel line to see if its kinked or bound up.

check your sparkplug wires,one of them may be arching. or, at right side of powerhead under shift slid, follow wiring from neutral point [aprox. 6 inches] to wire connector. jiggle the connector while the motor is running to see if it gets better or worse. you might even check the oilpump rod lever [left side of powerhead] to make sure it's not sticking. that last part would be for the RPM spike. i remember a simular issue last summer on a HPDI. it's problem was a arching plug wire. Good Luck

i checked the inside of the sparkplug wires, a couple of them look rusted. there was none of that sparkplug wire grease left in them either.

just got off the phone with yamaha. apparently this engine has had a service bulletin put out on it which calls for the replacement of the oil pump.

ill have to call the dealer now...

First off let me say that at idle out of gear it will feel rough as it is only firing on 4 cylinders at idle out of gear,they are designed that way from the factory,if it still idles rough after you put it in gear then you may have a problem

more question

im going to take it in and have the oil pump changed and a compression check done. since i bought this boat used from a dealer that got it at a repo auction, i have no information on its service history. i'd like to just get any major maintenance done to it now so that i don't run any risks. i'm planning to get the sparkplugs, sparkplug wires, have a 10 micron fuel filter installed and all fuel filters changed. what else should i have done?

i'd also like to get the impeller in the water pump replaced, but someone told me to just have the entire water pump changed instead of just the impeller. he said it isn't that much more expensive and that its better than just changing the impeller.

also, im having a little trouble with my water pressure gauge. sometimes it works, sometimes it doesn't. next time i take it out im going to check the line for obstructions or kinks. what should the line from the outboard to the back of the gauge have in it? water or air? is there anything else i should look for?

so i guess i could sum it up with three questions.

1 - what maintenance should i have done on a 5 year old hpdi with no history?

2 - go for a new impeller or just replace the entire water pump?

3 - should the water pressure gauges hose have water or air in it?

1. have throttle sinc. zeroed out and reset. [5min.job]
2. if old impeller is still in 1 piece, impellor only
3. water, [you mite have a kink or sharp bend in the line]

thanks for the help. didnt even think about the idle speed/throttle sync thing. ill be sure and have that done.

O2 sensor check. Have been hearing that O2 sensor can cause some of the problems your having.

Blaine0311

when you get all the maintenance up to date including having the lower unit oil changed while there doing the water pump,and you get the 10 micron filter installed and all.be sure to run yamalube and also use the ring free product and you should not have any issues with anything else.When they check your motor out have them tell you how many hours are on it also ok.

Yes Sir. - good call on the 02 sensor

should i put a little bit of seafoam in the fuel too to stabilize it and combat moisture?

the ring free is all you should need......

ok thanks. what prop with what numbers are you getting?

got it all done and it runs beautiful now.

it had 288 hours on it, and ALOT of overheats on the memory. so i had them replace the entire water pump.

Am having my 04 300 HPDI worked on, and they told me I had a ton of overheats- like 287 of them with just over 200 hours when they ran a diagnostic. Turns out it is real common with the Yammies when they use non-OEM gauges, in my case Champion gauges. Can cause a false read, and they said it was no biggie.

That's what they told the certified repair shop my boat is at anyway. Anyone else have this come up?

Why would a guage give the engine computer a false reading? I have a 225 hpdi w/triton gauges and never had a overheat or seen that many on a engine. Sounds like a false sensor.

My 225 HPDI shows alot of overheats too. The horn has never sounded on the engine yet it shows overheats. I think it also showed like 70 over revs. I dont think those are accurate either but I cant prove it.