Over Temp After Several Miles WOT

[reddrooster]

This is an 02 VMAX 250 ox66, on a Skeeter ZX250- I was running up the lake at pretty much WOT as fast as 71 and backed it down a bit to 68. After several miles, I get a overtemp alarm and it shuts down. I looked at the water pressure as it was shutting down and it bounced from 0 to 15 then 0. I was getting about 18psi at WOT before but wasn't looking when it overtemped. I changed the impeller last year. After it cooled down, I ran it around the rest of the day with no problem and about 18psi a@WOT.

The only thing I can think is *maybe* I picked up a plastic bag or something that blocked the intake but came off (hence the bounce of water pressure).

Any idea what happened? Do I need to take it back in for a motor test?

Thanks in advance!


Modified by reddrooster at 9:54 PM 8/23/2011

[Rich Z]

I would worry so much. Do a compression test after the motor is warmed up and keep a close eye on that psi gauge next time you running wot. Any drop from what you think is normal should be addressed asap. Poppit valve is the first place to look.

[reddrooster]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by Rich Z &raquo;</td></tr><tr><td class="quote">I would worry so much. Do a compression test after the motor is warmed up and keep a close eye on that psi gauge next time you running wot. Any drop from what you think is normal should be addressed asap. Poppit valve is the first place to look. </td></tr></table>

Thanks Rich...I assume (hope) you meant you wouldn't worry so much? We did a compression check a few months ago and all was well.

[Rich Z]

[Charlie206]

Are you running a hydraulic plate that was maybe a touch too high?

[reddrooster]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by Charlie206 &raquo;</td></tr><tr><td class="quote">Are you running a hydraulic plate that was maybe a touch too high? </td></tr></table>
Nope a manual jack plate. I looked at the water pressure earlier and it was fine.

[Neilslure]

Check your intake grates, if they are a little loose or have any damage, they could be diverting water at higher speeds. I had this problem when my boat was new, I would lose WP at about 55 MPH.

[reddrooster]

That's a great tip, Neal. I did just replace those grates a few months ago. Possibly got loose. The best I have heard from you guys is doesn't seem to be a big worry right now.

Glad I didn't hear "Oh no....your motor is about to blow with that one time over temp!"

I'll keep a close eye on the pressure Saturday when I run the lake and check the intake grates before.

[Tx 201]

Keep in mind alarms are there to warn you to shut down before you tear something up. Not great to get it hot, but it should be fine since you shut it down when the alarm went off. Clear any obstruction and then running the motor in midrange will cool it off quick.

Although, I did have one cylinder melt down without any alarms, the rest were just fine and the right temp. Mechanic left some gasket material in the water port shutting off cooling to #4. Yeah, dealer said it couldn't have happened that way.

[reddrooster]

Well I just verified the intake grates are clean and tight. Its still a mystery and you'd better believe I'll be watching the water pressure on Saturday.

[reddrooster]

Ran it yesterday and it started dropping pressure at about 65MPH. Water pressure runs about 18psi before that. I suspect it is more to do with RPMs than MPH.
I changed the impeller last year but this sounds like the most obvious culprit..the impeller.

Hummm...maybe it was two years ago that I did the impeller? Duh!

[reddrooster]

Well, I still have the problem of the water pressure dropping. Happens after at about 65 MPH. New impeller didn't help. I also lowered my jack plate just to see if it helped. I usually don't mess with adjusting it but tried that as well. Didn't help.

I had a new gauge installed a few months ago after it froze last winter. I would have thought it was just a bad gauge but it actually over heated one day at WOT. That caused me to start watching pressure closer.

Any ideas what could be causing this new issue? I used to be able to run 70 without losing pressure. Of course I don't need to run that fast but don't like having an issue unresolved!

Thanks!

[Rich Z]

Have you ever cleaned the poppit valve or replaced it with a new style one?

[reddrooster]

I have not. I just read all the threads on the poppit valve and it sounds like a possible canditate.

However....

If I understand the poppit valve operation though, it bypasses water. A dirty or clogged valve will bypass all the time and you will have lower wp all the time. My wp is fine 18psi at highter speed, until I reach 65mph+. Then it drops out to 12 and fades to ~3. I slow back down and it returns to 18psi.


Modified by reddrooster at 8:01 AM 11/13/2011

[reddrooster]

One more bit of information that could be relevant. A few months ago I smacked a log while on plane. It broke out the port side pickup grate. I replaced both sides. My shaft is not bent only the nose and grate saw any damage.




Modified by reddrooster at 9:11 AM 11/13/2011

[Rich Z]

18psi is ok for wp but this may not always be a true psi. Your gauge may be off by a little bit and in actuality you maybe only running 12-15psi which is still ok but that would indicate a dirty poppit valve. My other theory is that, and I found this to be the case in quite a few motors, is that the poppit valve spring is weak and does not maintain its strength. I stretched out a few before and they work just fine now. I can see my psi gauge reach almost 30 psi in the winter and than all the sudden it will drop to 22 psi indicating opening of poppit valve. Think about how the lake water temperature or air temperature has an affect on any kind of metal. When it’s warm the metal is softer and when it’s cold the metal becomes more ridged or stiffer. You can purchase a new spring and new style valve for very little and I’d bet it will cure your problem. Hope this makes sense…

[mdtritn21]

When you changed the impeller did you look at the whole water pump. Looking at you skep you run in sand a lot and it may have damaged the pump housing enough to need replacing.

[reddrooster]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by mdtritn21 &raquo;</td></tr><tr><td class="quote">When you changed the impeller did you look at the whole water pump. Looking at you skep you run in sand a lot and it may have damaged the pump housing enough to need replacing.</td></tr></table>

Actually the skeg de-painting only happened last week on Sam Rayburn (13 ft low). My impeller was changed at the dealership this time. I doubt (hope), they would reinstall a damaged pump housing.