1997 Ski Nautique Ford 351PCM Won't Start

[Peter6000]

got the video done enjoy

Peter

[97nautique*]

I just watched it, thank you for it very helpful. I will do the test. You said if the channel in there is dirty, I should clean it. How do you recommend I do that?

[97nautique*]

I did the tests and here's the outcome. The valve was 90 degrees when I measured this.

- Left wire, 12.34 volts, good getting power.

- Right wire also has 12.34 volts when the boat is not running but has ignition on.

I took off the IAC and it worked as depicted in video. I cleaned out the channels and the gaskets because they were very dirty.

- While the boat was running I got 11 volts at the left wire and anywhere from 7-5 on the right wire. It was seven when it started cold and then as the idle went down the volts went down.

I didn't start the boat with the throttle after I cleaned out the channels and it fired right up cold.

[Peter6000]

I did the tests and here's the outcome. The valve was 90 degrees when I measured this.

- Left wire, 12.34 volts, good getting power.

- Right wire also has 12.34 volts when the boat is not running but has ignition on.

I took off the IAC and it worked as depicted in video. I cleaned out the channels and the gaskets because they were very dirty.

- While the boat was running I got 11 volts at the left wire and anywhere from 7-5 on the right wire. It was seven when it started cold and then as the idle went down the volts went down.

I didn't start the boat with the throttle after I cleaned out the channels and it fired right up cold.

Looks like the valve and valve control are ok, and your bypass air channel was clogged.

Sent from my SAMSUNG-SM-G870A using Tapatalk

[97nautique*]

So do you thing the clog was the issue all along?

[Peter6000]

Well it makes sense the bypass opens on start up to provide extra air, if its clogged the engine does not get enough air opening the throttle fixed that problem.
Is it starting with throttle in idle all the time now.
Peter

[SilentSeven]

Is the problem solved?

Peter6000 - really enjoyed the videos on the sensor checks. If I can ask, what's your background....you operate like a professional mechanic. I saw you mentioned you had swapped out the factory ECU on GT-40 with a different unit....

NautiqueJeff - might want to consider some sort of sticky for both of those videos for other GT-40 people trying to sort out run issues.

[97nautique*]

I think thew issue is solved, but I will wait to say for sure.

[97nautique*]

I have started the boat around 3-4 times today and none of my starts need throttle. I think this particular issue Is solved, but I still need to do the other manifold.

[Peter6000]

I have started the boat around 3-4 times today and none of my starts need throttle. I think this particular issue Is solved, but I still need to do the other manifold.

Thats great news, and yes as mentioned earlier you got seriously lucky with not having any internal engine damage.
The exhaust and elbow are not cheap but sure cheaper than a rebuild.

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[mtrader]

I couldn’t t figure out to start a post so I thought I could add to this thread ….My gt40 1998 air nautique was running great and then it died on me last week. At first I thought I ran out fuel but that wasnt it. After some troubleshooting I found I have low compression, mid 30s, 60s, and a couple zeros. Not good . But it appears the spark plugs are clean. The oil is clean not milky. Didnt overheat on me either. Risers are old but I only run it in fresh water . Owned it for about 12 years. 700 hours on the original motor. Ive done basic service on it like plugs, cables, filters etc. and I always watch the temperature. One time over 2 years it overheated from a bad impeller but it didnt have any issues except the exhaust tubes look like they leak a lil bit of water here and there. I think the muffler is in need of repair or replacement too. Boat takes in a bit more water than Id like to see.

any suggestions on the low compression? I tried putting in some marvel mystery oil a few days ago through the plugs to Let it sit there but Im hearing the heads may be bad. Not sure how much damage there could be since it didnt overheat or anything. Any ideas would be greatly appreciated. Oh one more thing, earlier this summer I left the gas cap off and it rained one day. I thought maybe a lil water in the fuel but the water separator was good. The motor did seem to bog down a few times but I put isoheet in the fuel and it went away. When it died on me I thought it was maybe the fuel also…unfortunately it seems more complicated.

[MN Ryan]

Zero compression? Yikes.

[Jonny Quest]

Typically, "running great" to "low compression" in the span of an hour or 2 doesn't happen without something catastrophically going wrong. If your compression numbers are truly as you stated, it's no wonder that your engine won't run. A full rebuild is about the only way to correct your compression issues. First, however, you need to find out what happened to cause the low compression condition. Ford numbers their cylinders 1 - 4 on the driver side and 5-8 on the passenger side (front-to-back on the numbering). Can you provide compression numbers by cylinder?

JQ

[Scooter G]

Zero compression would indicate bad valves, stuck valves, or possibly blown head gaskets (you would have other visible signs with head gaskets).
You would still get a little compression reading if the piston rings were shot. 700 hours with maintenance shouldn't be giving you this kind of headache.

[jpwhit]

Are you positive your compression gauge is sealing up properly? It’s pretty rare to have zero compression. Did any cylinder read over 100? Can you post all the reading?