New Boat- WOT speed, RPM and water temp questions

[mikeg205]

Follow fuel line from inline filter back to fuel tank.. pump has 2 fittings at bottom. You will need to remove pump. I replaced fuel supply, return and fuel pick up in tank. One day my rpms maxed out at 2500, but I got noticeable sound due to throttle being open.

The plugs always tell a good story of how things a burning. So please post a pic of them.

Sent from my SM-G955U using Tapatalk

[Bartnich]

Check the fuel pressure.

Which temperature sensor did you check? The one that matters has two wires, not only one. Remove the fuel line from the pump and check the inlet screen- it may be clogged.

If the RPM climbs smoothly from idle to about 3000-3400 RPM and stumbles as it tries to increase, it's most likely a fuel system issue.

Don't think you can really solve this on the trailer- you can't. Running without load IS NOT the way to deal with these problems.

Hi Jim,

Yes, I checked the temp sensor with two wires. I think it was not registering much change at the gauge due to the fact that the thermostat was likely toast and the water temps at the lakes were in the 50's.

I will check the inlet screen and am in the process of getting a new thermostat. So 143 or 160 for this engine? I've seen both suggested for this engine.

My ability to get out is going to change drastically come Tuesday when the weather turns, so I'm trying to check off as many boxes as possible before then to have less to mess with in the spring.

Thanks again!!

[Bartnich]

Follow fuel line from inline filter back to fuel tank.. pump has 2 fittings at bottom. You will need to remove pump. I replaced fuel supply, return and fuel pick up in tank. One day my rpms maxed out at 2500, but I got noticeable sound due to throttle being open.

The plugs always tell a good story of how things a burning. So please post a pic of them.

Sent from my SM-G955U using Tapatalk

Thanks Mike, I will check the inlet. I will also try to post come pics of the plugs later today if I can get around to pulling them again.

[Bartnich]

Thanks Mike, I will check the inlet. I will also try to post come pics of the plugs later today if I can get around to pulling them again.

Here are pics of the plugs. Keep in mind that the engine was fogged a couple weeks ago and I only ran it in the water once since then for 30 minutes and then ran it at idle for a bit for the compression test.

[mikeg205]

Last one looks a bit ashy - wonder if they all looked that way before fogging - full tune up next year I recommend.

[Bartnich]

Last one looks a bit ashy - wonder if they all looked that way before fogging - full tune up next year I recommend.

That one was starboard side furthest to the stern. Could that be due to a lack of fuel for some reason? Is there a way to make sure the injectors are spraying properly? Anyway to clean them?

[JimN]

Hi Jim,

Yes, I checked the temp sensor with two wires. I think it was not registering much change at the gauge due to the fact that the thermostat was likely toast and the water temps at the lakes were in the 50's.

I will check the inlet screen and am in the process of getting a new thermostat. So 143 or 160 for this engine? I've seen both suggested for this engine.

My ability to get out is going to change drastically come Tuesday when the weather turns, so I'm trying to check off as many boxes as possible before then to have less to mess with in the spring.

Thanks again!!

The two-wire sensor doesn't connect to the gauge, at all- it connects to the ECM. The one that connects to the gauge only has one wire. BTW- don't be lulled into complacency by thinking that the engine temperature is OK when everything else says it's overheating- temperature sensors don't work in air, only when they're immersed in liquid.

If you want to check for codes, use a scan tool or if you can't find one, you can use a paper clip- this method has been described many, many times.

Your plugs look pretty normal.

What makes you think the thermostat is toast? Use the 160 degree version unless you want to waste gas.

[Bartnich]

The two-wire sensor doesn't connect to the gauge, at all- it connects to the ECM. The one that connects to the gauge only has one wire. BTW- don't be lulled into complacency by thinking that the engine temperature is OK when everything else says it's overheating- temperature sensors don't work in air, only when they're immersed in liquid.

If you want to check for codes, use a scan tool or if you can't find one, you can use a paper clip- this method has been described many, many times.

Your plugs look pretty normal.

What makes you think the thermostat is toast? Use the 160 degree version unless you want to waste gas.

Thanks Jim, so what is an easy way to confirm the water temp sensor and gauge are working? I figured the thermostat was toast because the gauge never got past 130 degrees and when I removed it, it was a bit rusted up and has clearly never been swapped out because the housing bolts were still painted on.

[JimN]

Thanks Jim, so what is an easy way to confirm the water temp sensor and gauge are working? I figured the thermostat was toast because the gauge never got past 130 degrees and when I removed it, it was a bit rusted up and has clearly never been swapped out because the housing bolts were still painted on.

The easy test is to put the thermostat in 140-160 degre water and see if it opens. If it’s original, a new one is cheap insurance.

Measure the sender’s resistance at room temperature- then, make it very cold and put it in hot water. If the resistance doesn’t climb when it becomes cold and decrease as it becomes hotter, it should be OK. I have posted the Chevy resistance chart about 100 times- it has to be here, somewhere.

[Bartnich]

The easy test is to put the thermostat in 140-160 degre water and see if it opens. If it’s original, a new one is cheap insurance.

Measure the sender’s resistance at room temperature- then, make it very cold and put it in hot water. If the resistance doesn’t climb when it becomes cold and decrease as it becomes hotter, it should be OK. I have posted the Chevy resistance chart about 100 times- it has to be here, somewhere.

Ok, I will confirm temp gauge works tomorrow. So getting back to the original potential thesis, is it possible that since the engine will not warm up above 130 (assuming gauge works and thermostat does not) that the EFI is limiting RPMs? The indmar manual says these engines have a phased warm up and full RPM is not available below 140 degrees.

[JimN]

Ok, I will confirm temp gauge works tomorrow. So getting back to the original potential thesis, is it possible that since the engine will not warm up above 130 (assuming gauge works and thermostat does not) that the EFI is limiting RPMs? The indmar manual says these engines have a phased warm up and full RPM is not available below 140 degrees.

There’s no warm up phase on a ‘95 model- it’s like cars from that time: get in, hang on and go.

If this were my boat, I would change the thermostat and run it- if the temperature is stable and close to the thermostat’s rating, I think it can be crossed off of the list of causes, assuming there’s no big performance change.

Does the exhaust smell like gasoline?

[Bartnich]

There’s no warm up phase on a ‘95 model- it’s like cars from that time: get in, hang on and go.

If this were my boat, I would change the thermostat and run it- if the temperature is stable and close to the thermostat’s rating, I think it can be crossed off of the list of causes, assuming there’s no big performance change.

Does the exhaust smell like gasoline?

I haven’t noticed a gas smell from the exhaust, but I may have been upwind every time I took it out.

When did the warm-up phase start in the Indmar engines? The only reason I come back to that is the fact that it is specifically outlined in the 1994-2004 Indmar owners manual.

Thanks!!

[Poorhouse]

OP - My Indmar manual says the same thing. Based on that I would assume you are not getting full RPM at 130.

For reference my '96 temp is at 160 when warmed up. It pulls above 4k RPM at temp. We take it easy until it's warmed up so I can comment on max RPM below that temp.

I wouldn't worry about the gauge wiring or sensors at this point. Change the thermostat first as it's rusty and not moving during the warm water test. See how it does with the new thermostat then take things from there.

[JimN]

I haven’t noticed a gas smell from the exhaust, but I may have been upwind every time I took it out.

When did the warm-up phase start in the Indmar engines? The only reason I come back to that is the fact that it is specifically outlined in the 1994-2004 Indmar owners manual.

Thanks!!

That manual needs to include info that was introduced well after 1994- it's an awfully broad time range, IMO. Factory manuals are much more specific to year- the one we got in '98 had 1997 at the top and new engines were introduced in 1999 and 2000, so we got more manuals because of the changes. IIRC, staged warm-up came in when they added the Gen 3 engines like the 5.3L, 6.2L and 8.1L, etc. I think the Cadillac engine had it, too. That was added because they had engine failures because too many schmucks got it, fired it up and went WOT as soon as everyone was in the boat.

Look at the transom, around the exhaust flaps- if you see soot, wipe the inside of the flap and if it has a lot of carbon deposits, it may be running rich, but the plugs didn't look like it.

[JimN]

OP - My Indmar manual says the same thing. Based on that I would assume you are not getting full RPM at 130.

For reference my '96 temp is at 160 when warmed up. It pulls above 4k RPM at temp. We take it easy until it's warmed up so I can comment on max RPM below that temp.

I wouldn't worry about the gauge wiring or sensors at this point. Change the thermostat first as it's rusty and not moving during the warm water test. See how it does with the new thermostat then take things from there.

It's always a good idea to let the engine warm up to normal operating temperature, but the ECM's control isn't so specific in the older boats. Running at 130 just makes the engine less efficient.