Couldn't get skiiers up after changing props... plug gap?

[mancho]

I think I'm in the right forum, so don't kill me if this needs to be moved... it's not really a "repair" topic as much as a new boat owner and having general questions.

Ok, so I'm back on the water this weekend w family and a friend and we can't pull a 100lb boy OR an adult out of the water.

My mechanic (that changed my flywheel... this thread: http://forums.iboats.com/showthread.php?t=479506 ) said the 19 PROP was more desirable to get me out of the hole faster than the 21 that I had on it. So I swapped him mine for 50 bucks and this weekend didn't prove that it was any better.

However, I have NOT tried to pull anyone prior on skis only tubing. SO I don't know if the 21 was better... only pulled tubes on that prop.

This boat is rated at 280 HP. After I emptied the cylinders of water from the hydrolock, dried them out I put in NON gapped new plugs. but a .1 gap compared to the spec'd .03 gap, is that a big difference if the firing is "that tardy"?

The mechanic that changed the flywheel gear didn't do a compression test, he said it sounded great. However, the water load and actual lake testing is different than running on muffs in the shop of course.

This has the GM V8 vortech engine (5.7 Liters) ... this boat.. I would think a big enough engine for a 20 foot boat.

So it's either the engine isn't putting out 280 HP, or I'm significantly loosing it somewhere. We had just 2 adults and 2 100lb boys and 1 50lb girl. Not significant weight with 3 sets of skis in this size boat. No other big weight besides my 40lb tool box.

Help ! Any suggestions is great.

 

[oldjeep]

Re: Couldn't get skiiers up after changing props... plug gap?

You hydrolocked a motor and all you did was to empty out the water and replace the plugs? My suggestion would be to find a better mechanic and make sure that he flushes the entire engine out, checks compression, oil pressure and does a water test.

 

[shrew]

Re: Couldn't get skiiers up after changing props... plug gap?

Lower pitch would pull a skier out of the water easier, not harder. High pitch will translate to a higher top speed, but slower hole shots. To pull a skier you really need the hole shot to get the boat up on plane a quick as possible. You don't pull skiers at high top end speeds.

 

[mancho]

Re: Couldn't get skiiers up after changing props... plug gap?

So the lower pitch 19 is better.. and no one is thinking the plug gap will make any difference from the factory setting? Hmmmmm so better prop, still need more BANG out of the hole. Maybe a 4 barrel carb over my 2 barrel? I know I need a new intake.

BTW< I forgot to add that I did the flogging and emptying of the water, since the hydrolock only occurred after shutting down and then re-attempting to start. So the lock was done at a start. So minor damage, no bent rods, etc. Yes, I'm sure the mechanic did much more than just fire it up... but I did inquire about the compression and he said it didn't need it.

 

[haley]

Re: Couldn't get skiiers up after changing props... plug gap?

I do not have a lot of experience with a set like yours, so can't offer something truly helpful. Would be great if someone with same boat could add some thoughts.

To me it seems the boat has ample HP for what you are trying to do and I would focus on performance of the stock engine rather than determining which mod (trim tabs?) would yield the most benefit.

And I would start with the compression test.

 

[Limited-Time]

Re: Couldn't get skiiers up after changing props... plug gap?

That should be plenty of engine for a craft that size. 21 or 19 pitch prop. I'd start looking or you lost power. I have a simualr Boat that runs upper 50's and have pulled 3 skiers at one time with a 21 pitch prop.

 

[smokeonthewater]

Re: Couldn't get skiiers up after changing props... plug gap?

good advice above and YES of course.... gap your plugs.... You are trying to troubleshoot your engine and you have a problem that you already know about..... It's a no brainer... Fix that first and then continue..... It's like pulling into an alignment shop because your car pulls to the left knowing that you have a flat tire

 

[EMC 1810SS]

Re: Couldn't get skiiers up after changing props... plug gap?

You are trying to troubleshoot your engine and you have a problem that you already know about..... It's a no brainer... Fix that first and then continue..... It's like pulling into an alignment shop because your car pulls to the left knowing that you have a flat tire

I like this, can I use it?

 

[mancho]

Re: Couldn't get skiiers up after changing props... plug gap?

LOL. thanks for the replies! and yes, I LOVE that alignment shop analogy...really brings it home

 

[QC]

Re: Couldn't get skiiers up after changing props... plug gap?

I think I'm in the right forum, so don't kill me if this needs to be moved... it's not really a "repair" topic as much as a new boat owner and having general questions.

These are always tough topics to place. No problem, we'll help narrow it down here and go forward.

Just so we have some baseline data to work from, do you have your WOT RPM and speed? GPS would be best, but the simplest test of engine performance is probably top speed. The best indicator of propeller selection is WOT RPM, so at least we'd have that out of the way. There are lots of things that can affect performance that are not engine related. This is not necessarily a direct correlation to your issue (hole shot), but the list is pretty good to help narrow down any performance concern with an I/O: http://forums.iboats.com/showthread.php?t=295070

 

[sschefer]

Re: Couldn't get skiiers up after changing props... plug gap?

LOL. thanks for the replies! and yes, I LOVE that alignment shop analogy...really brings it home

IF the Vortec somehow survived the hydro lock unscathed, (doubtful), get it to a GM Marine Mechanic before you run it again. This will at least prevent any further damage. I noticed also that you changed plug types... That's probably not a good idea, I believe the Vortec uses plug resistance changes to help in providing proper fuel/air ratio on a per cylinder basis. Changing the plugs to a different type almost always results in poor performance.

 

[mancho]

Re: Couldn't get skiiers up after changing props... plug gap?

Oh... wait, I'm confused... the "plug resistance changes" ...what is that? I went to autozone with an old plug, and they gave me the updated replacement one for this engine... I just don't understand the phrase "plug resistance changes"

 

[smokeonthewater]

Re: Couldn't get skiiers up after changing props... plug gap?

he's talking about multiport fuel injection with a computer calculating air fuel ratio based on cylinder temps measured through resistance changes in the plugs.. Not relevant here though since you already stated that you have a carburetor....... carry on

 

[sschefer]

Re: Couldn't get skiiers up after changing props... plug gap?

No offense but you also don't understand today's engine technologies vs. the old truck in the back 40. If Autozone doesn't have the direct replacement don't use them. Go to GM or your nearby Marine service center and get the plug that the engine calls for.

If this really is Vortec engine then the computer is capable of reading the resistance at the plug and determining cylinder pressure and temperature via ionization. If you change plugs because a recall say's you need to then the computer eprom needs to be re-flashed with the latest data. If you don't your motor will run like junk and you probably won't be able to pull 100lb skier out of the water..... Sound familiar...

 

[smokeonthewater]

Re: Couldn't get skiiers up after changing props... plug gap?

he said he was considering swapping to a 4 barrel carb instead of his current 2 barrel.... no computer controlling air fuel ratio there

 

[sschefer]

Re: Couldn't get skiiers up after changing props... plug gap?

Ahhh then it's not a Vortec.

 

[mancho]

Re: Couldn't get skiiers up after changing props... plug gap?

Hmmm, I used the word Vortec because the mechanic referred to it as that. Can you tell from this pic?

http://web.me.com/mark_armstrong/Site/Last_Import.html#20

Its a 1998 5.7L Mercruiser V8 with a 2 barrel carb.

 

[jollymon]

Re: Couldn't get skiiers up after changing props... plug gap?

Has the boat ever pull a skier up? Have you ever driven a boat pulling a skier up? You might want to take an experinced boater out with and learn the ropes.

It could be something as simple as were people are sitting in the boat. Is it a bow rider, can you have a coplue of people sit up front? How does it respond when everone is in the boat, does it come up on plane?

 

[mancho]

Re: Couldn't get skiiers up after changing props... plug gap?

No, I've never pulled a skier so as my wet wife is yelling at me from the water, I agreed, yes, I'm certainly at fault.

How much of just gunning it WOT (as much as the stick allows)... probably around 4500 rpm on the gauge, going straight .... can I get wrong? Meaning...

I have trim outboard all the way down

I go FULL down on throttle as far forward as I can

I also keep boat straight as possible.

Yes, 2 100lb children were in back, I could ask them to the front. I could put my 35 to 40 lb toolcase up front under a seat maybe.

You think that would make all the difference? The problem is we BOUGHT a boat with enough for 2 families, so 2 more adults and perhaps a child, dog, etc... do you think this boat is going to fail to pull up with just 2 kids and me I don't see how its going to pull up with another 200 to 300 lbs.

Just sayin!

Thanks for the insight, agreed sir that learning curve is part of it. I am hoping to get better, with 3 hours this past weekend and total of maybe 10 on the water to date.

 

[bear_69cuda]

Re: Couldn't get skiiers up after changing props... plug gap?

Hello,

Are there any soft spots in the deck?

It's possible the foam is waterlogged adding substantial weight to your problem.

A 5.7 alpha one drive in that boat should yank the arms out of a skiers sockets.

Good luck!