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Boat hates this hot weather: boggy/low power holeshots


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Since I got this boat, it's hated pulling up skiers when the ambient temps are over 90F and the humidity is high.  It runs great the rest of the year.

Things that are new in the past few years:

Cap, rotor, plugs, plug wires, alternator, ICM, fuel lines, fuel pump, both low and high pressure filters, thermostat, raw water pump, impeller, injectors (cleaned).

There are no codes.  Fuel pressure was fine last time I checked it (when I was also having this issue).

I'm thinking maybe it's just too hot under the doghouse.  The box is insulated, and the only opening to the atmosphere that isn't via tubes pulling air through the stringers is a tiny slit above the cupholders.  Running the blower doesn't seem to help.  I don't believe it's vapor lock since the boat always fires right up, even after heat soaking/changing skiers.

Thinking I might install a second blower, remove one of the rear cupholders and pull the air from there, and deposit the cool air right at the spark arrestor.  I figure if I wire that to the existing blower circuit, I'll be dumping cool air up high and pulling down low from the engine bay with the existing blower.  Might also consider running a 140F thermostat in summer.

Edited by UWSkier
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Maybe try a cooler thermostat? Oops, read your last line that you are going to do that. Overall, it helped a 95 I had.

Edited by Steve B.
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I know you say it's not vapor lock and doesn't sound like it is.   However, you could try the low pressure fuel pump kit that is installed prior to the high pressure fuel pump just incase the heat is causing fuel issue?  Could try laying a towel on the fuel pump and fuel lines that has been soaking in icy cooler water for a couple of ski runs to see if that helps?

  • Like 2
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Running the blower based on your description could aggravate the issue given the inlet side appears to be very limited therefore you are actually lowering the pressure in the doghouse.  The inlet air path should include the slots under the windshield as an air path to the engine bay, if those are blocked or not there that certainly becomes an issue.  But it sounds like once the skier is up, things are okay so it does draw enough air in from somewhere to provide the ~250 cfm needed for a slalom run.  Although at the start, heat has built up under the doghouse, there is no ram air or purging of air under the doghouse, any water in the bilge is lowering the air density some more which all add up to low density air that gets mixed with the same amount of fuel therefore potentially an over rich fuel mixture.  In addition the initial fuel amount is also now warmer than when running so that is an additional component of poor performance (but better fuel economy:-)

Things that should help - verifying the windshield base slots are open and do feed the doghouse, running blower between sets.  Your idea of additional air intake is a good one, I have done that on mine.  Open bottom of 2 cupholders at the back of the engine box, add a couple of dryer tubes to run the air up to the top / back of the doghouse, add a divider to the area around the spark arrestor so the tubes really only feed the engine.  Or Version 2, simply cut a reasonable sized mail slot to the doghouse, add a channel that feeds the divider with ambient air.  The MC Prostar had the very same issue and did exactly what you are thinking, just made a cup holder an intake hole, as did the latest TXI variant.  Is there a fuel filter / water separator located up high in the doghouse?  If yes, you could move it down lower out of the hottest air.

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2 hours ago, UWSkier said:

it's hated pulling up skiers when the ambient temps are over 90F

This time of year, you must ski at 4:00 am to get temps anywhere near 90.   :)

How about propping open the doghouse 1"-2" to test the theory that improved airflow will mitigate the issue?  Taking the necessary precautions to safeguard rope and toes.  

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Perhaps double check that the ICM has plenty of thermal paste under it.  They are very temperature sensitive.  @filftwalton changed his three times over a few years before he got one that worked correctly after the engine warmed up.  That was a crazy diagnosis involving two certified Indmar mechanics and a few shadetree guys like me.

  • Like 2
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Posted (edited)
3 hours ago, Cole2001 said:

Are engine temps staying the same when it’s hot out?

When running, yes.  It'll heat soak when we shut down switching skiers but by the time I tighten the line to pull the next man up, it's right around 165F, which is where it always seems to run with this current t-stat, even in 55F water.  Doesn't seem to be a cooling capacity issue.

3 hours ago, blk93jeepzj said:

I know you say it's not vapor lock and doesn't sound like it is.   However, you could try the low pressure fuel pump kit that is installed prior to the high pressure fuel pump just incase the heat is causing fuel issue?  Could try laying a towel on the fuel pump and fuel lines that has been soaking in icy cooler water for a couple of ski runs to see if that helps?

It's on my list of things I'd like to do just for funsies anyways.  If I'm getting any pump cavitation, that would help.  I do get the occasional cavitation at key up but I can't hear or see on the gauge if it happens when running.

3 hours ago, Woodski said:

Running the blower based on your description could aggravate the issue given the inlet side appears to be very limited therefore you are actually lowering the pressure in the doghouse.  The inlet air path should include the slots under the windshield as an air path to the engine bay, if those are blocked or not there that certainly becomes an issue.  But it sounds like once the skier is up, things are okay so it does draw enough air in from somewhere to provide the ~250 cfm needed for a slalom run.  Although at the start, heat has built up under the doghouse, there is no ram air or purging of air under the doghouse, any water in the bilge is lowering the air density some more which all add up to low density air that gets mixed with the same amount of fuel therefore potentially an over rich fuel mixture.  In addition the initial fuel amount is also now warmer than when running so that is an additional component of poor performance (but better fuel economy:-)

Things that should help - verifying the windshield base slots are open and do feed the doghouse, running blower between sets.  Your idea of additional air intake is a good one, I have done that on mine.  Open bottom of 2 cupholders at the back of the engine box, add a couple of dryer tubes to run the air up to the top / back of the doghouse, add a divider to the area around the spark arrestor so the tubes really only feed the engine.  Or Version 2, simply cut a reasonable sized mail slot to the doghouse, add a channel that feeds the divider with ambient air.  The MC Prostar had the very same issue and did exactly what you are thinking, just made a cup holder an intake hole, as did the latest TXI variant.  Is there a fuel filter / water separator located up high in the doghouse?  If yes, you could move it down lower out of the hottest air.

Boat has no issues hitting in-spec WOT RPM.  It's just getting it to happily gulp down that initial gasp of hot, humid air.  Once it starts pumping/drawing good quantity of air, it seems perfectly happy.  The windshield slots with the down-tubes are there.  As are the vents in the stringers/FibECS.  Problem is (maybe) that air is down low.

51 minutes ago, justgary said:

Perhaps double check that the ICM has plenty of thermal paste under it.  They are very temperature sensitive.  @filftwalton changed his three times over a few years before he got one that worked correctly after the engine warmed up.  That was a crazy diagnosis involving two certified Indmar mechanics and a few shadetree guys like me.

It's just dielectric grease that came with the new one, but I'll check to make sure plenty is gooped on there.

Edited by UWSkier
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1 hour ago, John I. said:

This time of year, you must ski at 4:00 am to get temps anywhere near 90.   :)

How about propping open the doghouse 1"-2" to test the theory that improved airflow will mitigate the issue?  Taking the necessary precautions to safeguard rope and toes.  

4:45 am.  :)

I can try propping it a bit next time out, though since the air gathers up at the top of the doghouse, I'm not sure if that'll help or not.

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I was going to recommend taking the dog house off for a few tries and see if it helps. (safety, blah, blah, blah.)

Only hates when under load vs no skier? 

  • Like 2
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18 hours ago, UWSkier said:

Since I got this boat, it's hated pulling up skiers when the ambient temps are over 90F and the humidity is high.  It runs great the rest of the year.

Things that are new in the past few years:

Cap, rotor, plugs, plug wires, alternator, ICM, fuel lines, fuel pump, both low and high pressure filters, thermostat, raw water pump, impeller, injectors (cleaned).

There are no codes.  Fuel pressure was fine last time I checked it (when I was also having this issue).

I'm thinking maybe it's just too hot under the doghouse.  The box is insulated, and the only opening to the atmosphere that isn't via tubes pulling air through the stringers is a tiny slit above the cupholders.  Running he blower doesn't seem to help.  I don't believe it's vapor lock since the boat always fires right up, even after heat soaking/changing skiers.

Thinking I might install a second blower, remove one of the rear cupholders and pull the air from there, and deposit the cool air right at the spark arrestor.  I figure if I wire that to the existing blower circuit, I'll be dumping cool air up high and pulling down low from the engine bay with the existing blower.  Might also consider running a 140F thermostat in summer.

Do you have cup holders on the aft end of the dog house?  My boat has three cup holders in the back of the dog house, right above them is an opening for air to get into the engine.  Wondering if your insulation on the inside of the dog house covers up an opening ?  I could also get more air in mine by removing the SS cup holder inserts.

 

IMG_6261.jpeg

Edited by Bozboat
  • Like 2
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14 hours ago, UWSkier said:

It's on my list of things I'd like to do just for funsies anyways.  If I'm getting any pump cavitation, that would help.  I do get the occasional cavitation at key up but I can't hear or see on the gauge if it happens when running.

I bought the kit from my local Malibu dealer when I was having vapor lock issues.  I know you can source all the parts else where for cheaper but it had the plug and play wires ready to go and made it easy.  

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1 hour ago, Bozboat said:

Do you have cup holders on the aft end of the dog house?  My boat has three cup holders in the back of the dog house, right above them is an opening for air to get into the engine.  Wondering if your insulation on the inside of the dog house covers up an opening ?  I could also get more air in mine by removing the SS cup holder inserts.

 

IMG_6261.jpeg

Same doghouse.  Same opening.  It's not blocked, but perhaps it's slightly restricted.  I'll try it without the cupholders, but it'll be a while.  We're heading out for the next 5 weeks or so after the 4th, and I won't get back out before then.  Was hoping to get out next Tue but not to be.

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@UWSkier - complaining that your boat doesn't like hot weather then telling us you are bailing from the cozy confines of Phoenix AZ for 5+ weeks ... come on, is just a dry heat.

  • Haha 3
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2 hours ago, Woodski said:

@UWSkier - complaining that your boat doesn't like hot weather then telling us you are bailing from the cozy confines of Phoenix AZ for 5+ weeks ... come on, is just a dry heat.

LOL not so dry lately.  The monsoon humidity got here close to a month early.  I'd love to bring my boat up to the nice cold waters of Northern WI with me as she'd love it, but alas, the camper's coming along instead.

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1 hour ago, UWSkier said:

LOL not so dry lately.  The monsoon humidity got here close to a month early.  I'd love to bring my boat up to the nice cold waters of Northern WI with me as she'd love it, but alas, the camper's coming along instead.

Well don't come to MN.  Been raining since May 

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ahopkins22LSV

Didn't the 2017 ish TXi's with the 6.0 Crusader engines have similar issues? I seem to recall many owners needing to prop the dog house open.

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2 hours ago, ahopkins22LSV said:

Didn't the 2017 ish TXi's with the 6.0 Crusader engines have similar issues? I seem to recall many owners needing to prop the dog house open.

Most added a second blower 

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1 minute ago, ahopkins22LSV said:

Similar symptoms though?

Yep.  Which is what's prompting me to try similar.

  • Like 1
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