Sluggish 320 TBI after de-winterizing

[zajata]

I have a 2004 Supra LTS with the Indmar Assault 320 TBI that I bought just under a year ago from the original owner which ran as expected all summer (WOT was ~4500). I did the standard winterizing process detailed on the sticky thread. Following de-winterizing, I put it on the water yesterday and noticed the engine running sluggish ... at first only getting up to 3200 RPM at WOT and then after a couple of faster accels & adjusting the throttle tensioner, the engine now runs at 4100 RPM WOT, which is still about 500 RPM shy of the specified range (4600-4800).

Parts changed during winterizing:
- oil & oil filter
- fuel filter (WIX in-line)
- spark plugs & wires changes w/in the last 50hrs
- fresh gas & Lucas oil fuel treatment

Symptoms:
- Sluggish acceleration above 3000rpm ... WOT at 4100 RPM
- Noticed some fuel/water in the bilge after running yesterday ... double checked lines at the tank & fuel filter and everything was dry.

Any thoughts on what I should proceed to next? I checked the distributor cap last season when I changed the plugs/wires and everything looked fine (brass connectors). I have not had a chance to thoroughly inspect the fuel lines around the engine when idling, but did not notice any fuel stains/leaks after running yesterday.

Thanks in advance!
-Zack

[CJD]

Burn the old fuel out of the tank before you worry too much. If it's still sluggish with fresh gas, then you can troubleshoot running issues.

[zajata]

Burn the old fuel out of the tank before you worry too much. If it's still sluggish with fresh gas, then you can troubleshoot running issues.

Sounds good - thanks!

[Zkdk3000]

Have you checked fuel pressure yet?

Zk

[zajata]

Have you checked fuel pressure yet?

Zk

Have not checked the fuel pressure yet ... how difficult of a test is this?

I did do a cylinder compression test this weekend. All were hitting 155 to 162 psi, until the last one, which would not get above 60psi. I realized I did not hook up the trickle charger during the test and my battery was reading 10volts by the end of the test (second to last cylinder took a couple of tries to get up 155 psi). My sincere hope is that the lack of charge limited the ability to get the crankshaft spinning fast enough to get an accurate compression test.

Here are the updated symptoms:
- Ran ~20hrs this season and have not gone much above 4000 RPM (after running up to 4500 RPM and beyond last year)
- Thermostat runs a little bit higher this year 180 - 185°F versus 175-180°F last season
- Some residual fuel shows up in the bilge ... replaced the packing seal & only minimal water in the bilge

- No appearance of damage to the stock prop (4-blade)
- Running same fuel as last year (90 Ethanol-Free) ... running new fuel eradicating the sluggish hole-shot as CJD mentioned

[Zkdk3000]

Have not checked the fuel pressure yet ... how difficult of a test is this?

I did do a cylinder compression test this weekend. All were hitting 155 to 162 psi, until the last one, which would not get above 60psi. I realized I did not hook up the trickle charger during the test and my battery was reading 10volts by the end of the test (second to last cylinder took a couple of tries to get up 155 psi). My sincere hope is that the lack of charge limited the ability to get the crankshaft spinning fast enough to get an accurate compression test.

Here are the updated symptoms:
- Ran ~20hrs this season and have not gone much above 4000 RPM (after running up to 4500 RPM and beyond last year)
- Thermostat runs a little bit higher this year 180 - 185°F versus 175-180°F last season
- Some residual fuel shows up in the bilge ... replaced the packing seal & only minimal water in the bilge

- No appearance of damage to the stock prop (4-blade)
- Running same fuel as last year (90 Ethanol-Free) ... running new fuel eradicating the sluggish hole-shot as CJD mentioned

I have the same motor it is very simple. You can rent one for free at the auto parts store. Follow the hard fuel line from the high pressure pump to the throttle body. Behind the throttle behind facing the transom will be a pressurized hook up valve with a black cap on it. Before hooking up the gauge relieve the pressure in the line. I believe there is a push button next to the valve to do so. Hook up gauge. Record readings during crank, idle, WOT on land and the same for under load while in water. Off the top of my head I believe the reading should be around 31psi once idling and WOT. Have you replaced your IAC since you've had it?

Zk


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[zajata]

Thanks for the run down on the fuel pressure test, I'll try to run through at least the loaded test this weekend (boat is on the dock lift).

The IAC is just the knock sensor, correct? I have not replaced it, just pulled it when I winterized and put the same one back in this spring.

Do you have a recommendation for the adjustment (if any) on the throttle position unit?

Thanks - Zack

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[Zkdk3000]

Thanks for the run down on the fuel pressure test, I'll try to run through at least the loaded test this weekend (boat is on the dock lift).

The IAC is just the knock sensor, correct? I have not replaced it, just pulled it when I winterized and put the same one back in this spring.

Do you have a recommendation for the adjustment (if any) on the throttle position unit?

Thanks - Zack

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Idle Air Control valve. Next to the TPS. Auto parts store look up 2000ish Chevy vortec $35. Plugs, fuel pressure, IAC I would focus on to start.

Zk


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[zajata]

Idle Air Control valve. Next to the TPS. Auto parts store look up 2000ish Chevy vortec $35. Plugs, fuel pressure, IAC I would focus on to start.

Zk


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Awesome - will give it a shot. Thanks again. -Zack

[scottschmitt]

Looks like you changed the wires recently. Maybe double check they are in the right order and you are firing on all cylinders.
When in doubt, check the parts last touched by human hands.

[zajata]

Looks like you changed the wires recently. Maybe double check they are in the right order and you are firing on all cylinders.
When in doubt, check the parts last touched by human hands.I changed the wires last year and it ran fine the rest of the season and I was very OCD about making sure I matched the correct cylinder to the distributor.

Fuel pressure checked out steady at 30psi under all the conditions (loaded and unloaded, idle, WOT). Compression is perfect at 180psi on each cylinder. Changed the impeller and still running just barely above 180F. WOT is 4100 rpm (down 10% from last year) and top speed is 37 mph (down about 10% from last year. I didn't change the IACV because it looked clean and the boat is idling fine right at 650rpm.

My next thought is the propeller. I took a couple of pictures and noticed a small ding, but looks very minimal. Any other thoughts? Holeshot still doesn't feel quite right but I'm just going off of memory.

Thanks. https://uploads.tapatalk-cdn.com/20170730/9a2a5f6f2f68e9168d8abf849e41c951.jpghttps://uploads.tapatalk-cdn.com/20170730/f8295afe5bd0ed6d19901c434357459a.jpg

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