Problem with 2004 200 HPDI - WOT won't exceed 4800

[nemako93]

Trying to chase down a couple issues......

Here is what has been done for Spring maintenance:

- Replaced main fuel filter, VST filter, canister filter after VST tank.
- New plugs, 10 micron Yamaha fuel/water separator element.
- New LP pumps, cleaned O2 sensor
- Compression #'s within spec/even across cylinders (slightly lower in bottom 2 which I have read is normal).

Had Yamaha tech check HP pump (680 psi) and pump in VST tank (50 psi). Pressures remain steady at speed all the way up to WOT. All cylinders fire in gear and spark has been verified. Engine idles low when started (500 rpm) and runs rough idling through the harbor..... seems sluggish overall. Idle rises to 1300 after cruising for a while.

The engine is on a 20 Mako (1993) and I am using a Yamaha 15.25x15M Saltwater Series prop. Should be turning about 5500 rpm WOT.

Not sure what to check next...... any help would be appreciated. Thanks.

[kracker1972]

what was the rpm when prop was installed?

[nemako93]

what was the rpm when prop was installed?

The engine turns 4800-4900rpm's WOT trimmed out with just me and about 60 gallons of fuel.

[kracker1972]

Have you tried a different prop? RPM's are con*****ed by it. Also what type of oil and gas are you using? Ethanol? Any kind of additives?

[nemako93]

I used the same prop with the old engine (carbed 200) and it turned 5500 rpm no problem. That is why I am perplexed as to what the issue is..... A 15 pitch is about as low as you can go...... I was actually expecting to need a higher pitch with the new engine (to bring the rpm's down a few hundred). 17 pitch seems about average for a CC in this size/weight.

[kracker1972]

are the throttle flaps opening all the way?

[nemako93]

Yes, I verified that when I rigged the engine.

[junebug08]

I am having a similar issue. 2000 150. going down the canal runs great. Open it up and only get to 4800. After running a while the engine runs very rough/shaking at idle. Started a week ago out of nowhere and only happens after the engine has been run at speed for a while and has had a chance to get hot. Mechanic has been working on it for a week trying to figure it out.
????

[99yam40]

Trying to chase down a couple issues......

Here is what has been done for Spring maintenance:

- Replaced main fuel filter, VST filter, canister filter after VST tank.
- New plugs, 10 micron Yamaha fuel/water separator element.
- New LP pumps, cleaned O2 sensor
- Compression #'s within spec/even across cylinders (slightly lower in bottom 2 which I have read is normal).

Had Yamaha tech check HP pump (680 psi) and pump in VST tank (50 psi). Pressures remain steady at speed all the way up to WOT. All cylinders fire in gear and spark has been verified. Engine idles low when started (500 rpm) and runs rough idling through the harbor..... seems sluggish overall. Idle rises to 1300 after cruising for a while.

The engine is on a 20 Mako (1993) and I am using a Yamaha 15.25x15M Saltwater Series prop. Should be turning about 5500 rpm WOT.

Not sure what to check next...... any help would be appreciated. Thanks.

If it keeps good fuel pressure and spark then I would be looking at cleaning the injectors and/or for any codes. If running lean it will cause major problems.
Have you verified the o2 sensor voltage to see if it is working properly?

Hopefully Rodbolt will chime in

[nemako93]

No codes according to YDS. I was starting to think maybe injectors as well, but do they throw a code? I will check the O2 sensor, which could be causing the starting, idle issues, but I was told that it has no input above 1500 rpm.

[rodbolt17]

monitor fuel pressure and ign timing at the problem RPM and load.
its the only way to verify it.
if you suspect an injector simply spray some premix down the air valves at the problem RPM and load and see if the engine reacts.

[nemako93]

Can the HP pump still lose pressure since it is belt driven? It puts out 680psi according to YDS. The MP pump stays at 50psi from idle to WOT.

[axolotl98]

Check another angle as well.
Is your boat clean of any marine growth or has it taken any rain or sea water in ?
Weight and increased drag can make all the difference without any issue motorwise...

[rodbolt17]

hp fuel should be about 625-725 PSI at ALL rpms on a 2.6L Z motor.

[nemako93]

Yamaha tech came back and the computer had an injector code stored. Turns out the injector driver has no output going to cylinder/injector #5. Planning to pull the injectors for cleaning/testing and replace injector driver. Being down one cylinder explains my top end loss and the rough running. Luckily, the powerhead is ok...... this was definately intermittent and I have only put a few hours on this season. I'll report back after I get things replaced.