Fuel issue indmar 325

[ktrojcak1]

99 santera 325 indmar. Just bought boat so I don’t know the history. When it’s towing around 10 to 15mph will run perfect for a few minutes and all of a sudden just looses power and starts shuddering and backfires but will idle. Turn off for a minute or two and works fine for a little bit and does it again . Runs great at idle or just above, and will run perfect all day long going 20 mph plus. When it happens if feels like the fuel pump is shutting off and your running on fumes. I have searched all over but mostly what I find is boats that will not run good over certain rpm.

[CJD]

Is it a carb or FI? Is the pump mechanical on the block or electric?

In general, your description is exactly how a failing fuel pump acts. The twist is usually a weak pump will not run well at high speed...meaning temperature may be an issue, but still fuel related. If you have a carb I would think vapor lock while running hard at lower speeds. If it is fuel injected, then 100% fuel pump related.

Of course this assumes you have changed your fuel filter, which is always the first step with engine problems.

[MJHKnox]

^^^ +1 on the fuel filter.

Not that it's related to your fuel issue, for a new boat to you, I would also check the simple tune up items at that start of the boating season - plugs, cap, wires. Easy replacements that could eliminate some headaches later. You may already be on top of that.

[ktrojcak1]

Fuel injection. I have put on new fuel line, and new filters. There are two fuel pumps (carter low pressure & the factory high pressure) also both fuel pumps are connected to the same wires.

[tretter7]

You sure it's not boat temp related? Mine will do stuff like that when the computer goes to shutdown mode if it's overheating. Usually this is because some crap is clogging up the transmission cooler. Boat can't flow enough cooling water and overheats. But at higher speeds the load is lower and the pump works harder, so the engine cools back down.

[ktrojcak1]

I’ll check all the cooling lines screen and pick up out but I’ve never seen it get over 160. I have to do some work on my gauges to cause half of them don’t work most of the time.

[CJD]

It sounds most likely the connection to the HP pump, or the pump itself is failing intermittently. If the low pressure pump is an add on, it could be pulling enough amperage to affect the HP pump.

[2500HD]

I would check your throttle position sensor. Also install a fuel pressure gauge up by the intake and see what it reads when this happens. I'll bet the pump is fine but this is the only way to know for sure.

[tracetrimble]

Hook up a fuel pressure gauge to the schrader on the rail, and watch the pressure while you drive. Should be around 48 psi pretty much all the time.

The problem with the gauges is almost definitely the MDC. Check my recent thread.

https://forum.supraboats.com/showthread.php?19457-2000-Launch-Dash-Rebuild

[2500HD]

Throw away the mdc. Here is my thread, Same boat.
https://forum.supraboats.com/showthread.php?17208-medallion-mdc-1600-delete-and-head-questions

[ktrojcak1]

Definitely going to change the gauges out and get rid of mdc thanks for all the info. In hope to fix issues I put new fuel pumps on and new filters. Problem still exist. I didn’t get a chance to get a fuel pressure gauge but I have a entirely new fuel system and new relay. It’s all not a over heat problem that I can tell cause it never gets over 160, but I do believe it’s going into limp mode. Which scan tool can I get to view the codes?

[ktrojcak1]

Also in checking every thing out I found that the warning light for the v-drive oil pressure wasn’t hooked up. Now that it’s connected the light never goes off. The gearbox has the right amount of oil. The oil looks and smells good, and doesn’t get hot to the touch. There are no problems or noises from any thing. Could the pressure switch be out?

[CJD]

Gotta love PO's! Yes, it is very likely the pressure switch is bad, as the V-drive itself is almost indestructible. Your last owner likely disconnected the light rather than actually fix something!?!

[MacGGE04supra]

Wondering if anybody can help. I have a 2004 supra gravity games addition but about a year and a half since it’s been driven had some work done to it got it out for the first time today it ran better than ever wide-open and at a lower Throttle it’s got a slite Sputter an idol it died a couple times my guests may be a fuel filter or something along the lines cranks and try’s to turn over plenty and fires just fine
Any input would be appreciated thanks

[2500HD]

Definitely going to change the gauges out and get rid of mdc thanks for all the info. In hope to fix issues I put new fuel pumps on and new filters. Problem still exist. I didn’t get a chance to get a fuel pressure gauge but I have a entirely new fuel system and new relay. It’s all not a over heat problem that I can tell cause it never gets over 160, but I do believe it’s going into limp mode. Which scan tool can I get to view the codes?

Throttle position sensor.

[ktrojcak1]

I finally got some spare time to hook the rinda up to the boat. The only fault code is engine over heat. Unless it was a quick spike when is was not watching, it never got hot. Now that I have the diagnostic tool I’ll go out on the lake and recreate the problem with the scanner hooked up to see if it’s actually over heating. If it’s overheating what is the first step( water strainer clean, can’t see any debris in intake) could it be sensor, impeller, water pump. Thanks for all your help

[nboardskier]

It sounds like you've got a lot going on. If you know you have sufficient fuel pressure to the injectors, then the problem must be ignition. I don't think overheating will cause it to sputter . . but then again, my boat doesn't have all of the electronics on the motor. Did you check the distributor cap? The problem you describe in the beginning sounds an awful lot like what my boat does when it gets condensation in the distributor cap.

[ktrojcak1]

Well I finally got around to going back to the lake. Changes temp sending unit and tps just to rule that out. I hooked up the rhinda while I was running and found that the engine is overheating or at least thinks it is. The gauge on the dash seems to be working cause if I run hard then shut down it heats up a little but instantly cools off when started. Computer on the other hand seems to think it’s getting up to 215 while pulling at load and puts me into limp mode but slowly cools back down and runs good again until it over heats. I know there are two different sensors for temp but why would they be reading so different?

[[email protected]]

I have the same model with similar problems this year. My temp gauge was reading 160 as well. So I thought I had water in the gas. I changed fuel filters twice and put water treatment in the fuel. Then I changed the raw water pump and thermostat and it seams to have taken care of it. Only had it out for an hour or so. Where did you get your scan tool? Just FYI my transmission switch was never wired either. I bought my boat when it was about 3 years old.

[ktrojcak1]

New impeller and thermostat, still not fixed. Next step new water pump, remove risers and inspect, and replace water lines. I bought the rhinda scan tool from their website.

[ktrojcak1]

Got it fixed
One of the fittings on the water filter was just loose enough to let the impeller suck in some air with the water
I took off the intake line to inspect and tried to blow through it an some air came out around the fitting tightened it with Teflon and boat runs flawlessly now thanks for all the help and suggestions

[SupraDs]

Can someone explain ktrojcak1’s fix? I don’t see how letting some air in the water system would produce the rough engine performance? Especially if the water temperature gauge isn’t showing an anomaly.

I’ve been trouble shooting the same issue: after 30 minutes of wakeboarding, the boat backfires and stumbles... I’ve been focusing on electrical gremlins (suspecting that increasing heat is causing increasing resistance) and fuel delivery problems (BUT I get a solid 30 PSI even when it backfires).
—
2001 Supra Launch v-drive with Indmar Assault

[tretter7]

Can someone explain ktrojcak1’s fix? I don’t see how letting some air in the water system would produce the rough engine performance? Especially if the water temperature gauge isn’t showing an anomaly.
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Have you ever tried to drink from a straw that's got a crack in it, and all you get is bubbles along with half the Coke you expected? Same thing. Easiest way to check if a temp issue could be causing this (and your gauge isn't picking it up) is to to the 5 gal bucket water flow test and make sure you have proper flow.