With four people, I can't get it up.
 

Hey all,

I wanted to get your opinions on what's going on with my 19-foot Mariah 1900Z. It has a 4.3L Mercruiser Alpha One.

Last night was the first time I had the boat out with three other adults, and I couldn't get it up on plane. One guy was sitting in the bow, one guy in the center of the back bench seats, my girlfriend as co-pilot and me.

The boat would start to come out of the water, and then the engine would start to rev up slightly. The bow was fairly high. I had the prop trimmed all the way down.

I know this isn't a spun prop -- the prop is literally brand new (not rebuilt). And the reason I have a brand new prop is that I thought the previous one was spun because it exhibited the exact same symptoms. So two spun props, I think, is highly highly unlikely.

Both props are 14.5" x 19p -- a good all-purpose size for my boat. When I take the boat out alone, it pops right up on plane, so it certainly has something to do with the extra weight.

What might be going on?

Re: With four people, I can't get it up.
 

I was a bit worried about the title this thread, I thought it was about group sex... :laugh:

It will take longer to get on plane with more weight on the boat, are you saying if you keep the thottle all the way down it never gets on plane?

It could be your trim limit sender is not set properly and the drive is not truly all the way down. In the fully lowered position the back end of anti-cavitation plate should be below level.

Re: With four people, I can't get it up.
 

That's correct -- with the throttle all the way down, it never gets on plane. It starts to come out of the water, then the engine RPMs increase at a fairly quick pace. It doesn't shoot up to redline or anything like that, but it's obvious that the engine RPMs are increasing, and the boat is no closer to planing out.

I'm wondering about the position of the trim as well. I'm not 100% convinced that the drive is all the way down when I think it is (and when the gauge says it is.) With my particular boat, a visual inspection is virtually impossible, as most of the outdrive is under the swim platform. And I would imagine a few degrees of tilt may be hard to see, but critical for getting up on plane.

I'm really really hoping it's not the engine coupler failing. Are there other symptoms of that?

Re: With four people, I can't get it up.
 

If your boat is anything like mine you can adjust the trim all the way down, and you will hear a change in the trim motor tone when it hits the dead stop.. To my knowledge the indicator does not limit the trim it just report where the sender unit says it is... It is quiet so you could do it with the motor off. The tone should change. Open the engine hatch if you have too...

Re: With four people, I can't get it up.
 

I agree with Z202.....at first i had some strange thoughts about the title. ;)

After i thought about it for a bit then i figured, stop eating at McDonalds but i just knew that couldn't be it...:shakehead:

I agree that it could be a trim sensor/sender unit that needs some adjustment since that 19" prop should do the job. Also, what about a pair of Smart Tabs? The Smart tabs would definitely help you plane quicker and stay on plane longer....

Re: With four people, I can't get it up.
 

Yeah, I wouldn't rely on the gauge to tell you when the drive is trimmed all the way in. It's sender could be out of calibration as well (there are 2 senders on the drive, one is for the gauge, and one is for the trim limit).

Trim it all the way down in your slip and have a look under. You should still be able to ascertain if the drive appears to be fully in.

Re: With four people, I can't get it up.
 

I'm not relying on the gauge -- instead, as 22empire suggested, I'm relying on the change in tone of the trim motor when the unit is all the way down.

But even upon hearing that change in tone, is it possible that the drive STILL isn't all the way down?

Re: With four people, I can't get it up.
 

i have this same problem with my shabah except it does plane out it just takes longer with more people and more beer.

im running a 14 x 19 ss.

yesterday when i was out i had one person up front,me driving, wife next to me and a friend in the back. it was pretty rough water and i could not get it to plane out at wot. ???

will it take longer to plane out since i have a smaller engine?

Re: With four people, I can't get it up.
 

No, it should then be all the way down. Unless of course there is a mechanical obstruction. The trim limit sender only keeps the drive from being trimmed out too much, which pretty much invalidates my original assertion, that lack of in trim is due to a duff sender. Sorry about that, should've had another coffee before I posted that... :(

Yes. Heavy loads + less horsepower = longer time to plane.

Re: With four people, I can't get it up.
 

Here's what I'm doing with the drive trim:

(Push and hold "down" button)

[Sound from drive unit: RRRRRRRRRRRRRRRRRRRRRRRRReeeeeeeeeee]

^

That's the bottom, correct?


(Release "down" button).

There's basically no way it couldn't be ALL the way down.

Then, whether I hammer the throttle or slowly increase speed, the bow comes up a bit, and as the boat tries to get on plane, the engine RPMs start to increase, and it the speed slows a bit. It feels similar to an attempted takeoff with the drive tiltled up, but it isn't. And again, with a brand-new prop, there's no way it could be a spun hub.

So if it's NOT the trim of the drive, then what? (Please don't say engine coupler. Please don't say engine coupler.)

Re: With four people, I can't get it up.
 

With your original prop you were able to get up on plane, right? If you put that one back on, does it still plane out?

If that still works, then defiantly not the coupler, but it doesn't make sense as to why the new prop wouldn't get you on plane either.

Re: With four people, I can't get it up.
 

Prop #1: 14" x 21p. Very good shape--no dings. Still, the boat wouldn't plane at all.

Since I didn't have a spare prop with this boat, at the suggestion of a repair place (and I agreed with them), I picked up a new prop because we all thought Prop #1 one was spun. Made sense at the time.

Prop #2: QuickSilver 14.5" x 19p. Brand new. The shop installed it, and I watched them do it -- no problem there.

With Prop #2, if I'm alone in the boat, it comes up and planes just fine. With three other people, no go. This makes sense, as the lower pitch would yield a little more power out of the hole. But still... not getting up on plane with 4 adults and a 4.3L /195 HP engine? I mean, jeez, my grandparents' old 55-horse Evinrude outboard could do that.

The engine seems to be making good power...it's not missing, sputtering, or anything like that. It's totally smooth. And there's a ton of wake and prop wash being produced also, so it's putting at least SOME RPMs into the water.

(Maybe the previous owner opted for Mariah's largely unsuccessful "newly improved hull lining, now made with extra lead!") :rolling_laugh:

I'm totally at a loss.

Re: With four people, I can't get it up.
 

So if it starts to over rev, the question is, is it ventilating or cavitating? Is your ventilation plate all in tact? Is the back of the new prop showing any burning or funny marks?

What model 19p prop did you get? Maybe has bad shape or too much/little cupping?

Re: With four people, I can't get it up.
 

The new prop is a QuickSilver Black Diamond XT Aluminum 3 Blade (14.5 x 19). Seems like a logical choice. I watched the tech take it out of the sealed box, so there's no chance it's a case of mistaken identity.

There was a hub kit as well, with all the associated hardware (locking ring, thrust washer, etc.). Everything was installed as you would expect. And for a tech with 20 years of experience putting a prop on a totally typical Alpha One, I mean, that's a no-brainer, right? I guess it's possible they grabbed the wrong hub kit and the thrust washer isn't the correct one, HOWEVER, the previous prop (the 21p) didn't require a hub kit and exhibited the same symptoms.

The ventilation plate is completely intact -- no problem there. And there's no evidence of burning or marks at the back of the prop. The skeg has a small chunk missing (maybe a half-inch by 2 inches) on the trailing edge, but there's no way that could be the problem.

Re: With four people, I can't get it up.
 

Sure seems like it would be a fine all around selection. Nothing specialized about it that would make me thing it's a bad blade design for your setup.

"Recommended for speeds less than 50 MPH and applications less than 250 HP"

The different hub kits are just the internal metal part of the hub that connects to the splines on the prop shaft. If he had the wrong kit, it wouldn't have fit on the shaft. Basically makes it so the same prop can be run on a volvo as a merc... just swap out the hub kit.

I agree, I don't think that small of a piece missing from the skeg would make that difference.

I'm starting to agree with your assessment of having the new lead lined hull.



If the coupler is shot, you should smell the rubber burning when it slips.

Here's some text from iboats on how to test the coupler.
"WITH THE ENGINE OFF, shift into fwd and stand on a prop blade while having someone look at the inputshaft behind the motor. If it turns and the motor dosent, the coupler is bad."
http://forums.iboats.com/showthread.php?t=311043

Re: With four people, I can't get it up.
 

After reading the tread so far, a couple of questions come to mind:

With just you in the boat, what is the WOT speed of the boat, and at what RPM? If the coupler was slipping, one would think it would be doing it when the engine is under load, no matter how many people are in the boat.

The next one might seem trivial, but when was the last time your engine had a tune-up? Just like our cars, a properly tuned engine produces more power, and runs a whole lot better!;) Is the fuel filter clean?

When was the last time the flame arrestor was cleaned? If it's dirty, it could be holding the engine back too.

Is there fresh gas in the tank? Old stale gas can create all kinds of issues.

Hope your problem is one of these simple fixes! Keep us posted. :)

Re: With four people, I can't get it up.
 

The engine really does seem OK. It had new plugs this spring, an oil change last fall (before being winterized) and the gas is fresh clean. (And less than half a tank, so the extra weight of a full fuel tank isn't coming into play.)

Not sure about the flame arrestor. Still, the engine seems smooth -- it always starts without a problem, doesn't hesitate or miss, doesn't sound clunky or rough.

With just me in the boat, the WOT RPM is about 4600. The speedo reports 44 mph, but I've yet to test it with GPS.

I agree with you about the coupler -- if it was going bad, it would be kinda obvious.

I'm taking the boat out now with my girlfriend to see what happens with two people. (For the record, she's 5'4, 130#, if that plays a role in any of your calculations.) :wink_thumbup: I'll make a note of the WOT RPMs if we can get it to plane.

Re: With four people, I can't get it up.
 

Well I don't know, if you come back here and post up that you couldn't get it up with just the girlfriend, we may just have to refer you to a doctor, for some pills. :D

Back on topic; is your bilge empty? Check the ski locker too. There were some members who were missing a drain hole at the back to the engine compartment. Result was the ski locker holding a lot of water.

Re: With four people, I can't get it up.
 

OK.

With just my girlfriend and I, no problems whatsoever -- it quickly planed out. So apparently the problem is occurring when someone sits on the back bench seats.

Could an extra 200 pounds back there really cause a 195HP boat NOT to get up on plane? Especially if there's another 200 pound person up in the bow?

To answer other questions: Bilge is empty, ski locker is dry and contains only an old canoe paddle, trailer is definitely not still attached. :rolling_laugh:

Last night, with the two of us, on calm water, WOT was 4400 RPM.

Re: With four people, I can't get it up.
 

It still sounds to me like your engine is not making the power it should for some reason. Perhaps some kind of exhaust restriction? Just a guess...

How many hours are on the engine? Have you done a compression check? I'm sure this is not what you want to hear, but perhaps the engine is simply worn out?

Your boat should be able to pull a water skier out of the water, even with 3 or 4 people in the boat. Not sure if you tried that, but I can imagine the results based on your other comments.

If I were you, I would take an experienced marine mechanic for a ride in your boat along with 1 or 2 other people, and let him see what it does first hand. Perhaps then he would be better able to diagnose the problem.

Re: With four people, I can't get it up.
 

Mike-- your ability to see the future is spot-on. I'm leaving in a few minutes to do exactly that. The top guy at the shop said, "Bring it over, I'll grab a few guys here, and let's take it out on the water."


I'll report back with what's going on and what they find.

Re: With four people, I can't get it up.
 

Just got back from the shop. (An authorized Mercruiser facility.)

Went out on the lake with their lead tech and two other techs (four of us total.) And of course, the boat performed perfectly. Popped right up on plane. With three guys across the back, it would still plane out, although it took longer, as you'd expect.

They were happy with the engine performance, WOT RPM (which was 4300) and the overall performance.

They had two possible explanations for what happened:

1. There were either weeds around the prop (I'm nearly sure there weren't, but not 100% sure) or we were taking off with a relatively heavy load in the midst of a weed field. Certainly possible given all the rapid weed growth in Madison lakes lately.

or

2. Something intermittent that will surely get worse and reveal itself as time elapses.

We left it as, "Well, if it happens again, bring it back, and we'll take a look at it again."

I guess that's all that can be done at this point. I think I'll bring a camcorder along for a while if it starts happening again. :rolleyes:

Re: With four people, I can't get it up.
 

Oh... and they specifically recommended to NOT switch to a 17-pitch prop at this point, as it would likely over-rev at wide-open throttle. Had the WOT RPMs been considerably lower, I think they would have recommended the 17.

Re: With four people, I can't get it up.
 

IMHO, you should be between 4700 to 4900 rpm with the Quiksilver Prop.

I base that on my setup: 18 ft Talari, 4.3 2bbl, 14.25x 19 Stilletto prop.

Can the encapsulated foam on a Mariah get waterlogged?

Re: With four people, I can't get it up.
 

I asked about waterlogged foam also, as well as the sundeck. That doesn't seem to be the case, as the whole boat is dry (not leaking anywhere), shows no signs of dampness, and was stored indoors over the winter.

The repair techs said that if there's a waterlog situation going on, the boat will almost certainly drip when it's out of the water for a period of time. When they had it in the shop a week ago, there was nothing that seemed obvious -- it wasn't dripping. It was indoors, on a trailer, for three days.

Re: With four people, I can't get it up.
 

One thing peaks my interest...

When the boat couldn't get on plane, it was still revving higher. This could essentially mean only 2 things. The hub was slipping, or the coupler was. I agree with what's been said - the hub was new and fit perfectly by a trained technician. I really don't think it was the coupler either... I'm at a loss on this one!!

If the engine revved higher, I don't think you have a compression, flame arrestor, spark plug issue, etc. If it's revving, it's making horsepower. Something was obviously slipping, but I hate to guess.

Re: With four people, I can't get it up.
 

I'm just not technically proficient enough to know which things could possibly present an intermittent problem. Can a coupler slip intermittently? Can a thrust washer slip intermittently? Is there something else that can cause a periodic problem but be perfectly fine other times?

I guess that's why I'm not a sterndrive tech!

Re: With four people, I can't get it up.
 

A slipping hub can be an intermittent problem at the beginning based on the load that it's under.

I have had the same happen to me, but it's been the things that you ruled out: slipped hub, debris or stick hooked on the outdrive, trim not tucked in.

Re: With four people, I can't get it up.
 

That's exactly why the only explanation I can think is that the prop is slipping in the water... ventilating, cavitating, badly shaped blades or something like that. But the prop seems to be rated as a good all around prop.

abillmann: where are you located? Maybe someone is close enough to you to try a couple different props.

Re: With four people, I can't get it up.
 

No, three: Or it was cavitating. That is what I've suspected from the start. But I'm new to this boat, engine and drive system, so I've kept quiet :).

Jim

Re: With four people, I can't get it up.
 

You're right. Could be cavitating as well. I've never heard of cavitating on a deep water start, though.

Then I remembered an experience from last year. I ran over a water-logged 2 X 4 and just so happened to split it directly in the middle. The wood was basically wrapped around the lower unit, directly in front of the prop. That caused major cavitation and did exactly like what we're seeing here. I knew something was wrong right away - felt like the prop flew off!

I suppose a lot of weeds stuck in front of the prop could cause this same thing. Hopefully that's all it was and you don't experience it again. Here's an idea, have the girlfriend bring out a bunch of her 120 lb. friends instead of you bringing your 200 lb boys!!!

Re: With four people, I can't get it up.
 

I'm in Madison, WI. Great area for boating -- three large lakes, two of them urban, one rural, interconnected by a river. Lotsa weeds this time of year, though.

Could someone explain exactly what a cavitating prop does/looks like? Is that ultimately a prop problem, or a lower unit problem? There's no damage to the prop, nothing that looks burnt, or anything that looks scratched or worn. Again, the prop is 14.5 x 19p, brand new, still in mint condish. Is cavitation something that could be intermittent? Based on what conditions?

Prior to the new prop, I had a 14" x 21p that exhibited the same symptoms. I bought that prop used, and thought it was spun -- that's why I have the brand-spankin' new one. The 19 is definitely better than the 21 (as far as hole shot is concerned), but still...on Saturday night with four normal-sized adults, it was NOT going to plane.

Today, the boat ran perfect -- with four adults, there was no doubt it was coming up, and quickly got on plane. Ran beautifully. Previously, though, there was NO WAY it was going to happen.

I personally feel like there's some sort of intermittent slip going on in the lower unit, but I have no idea what it could be. There's certainly no chugging/grinding/grunting or anything that seems obviously wrong.

Could the hydraulic trim pistons (or whatever they're called) stick when the drive isn't all the way down?

Re: With four people, I can't get it up.
 

Ryan, man, you're preaching to the choir! Amen, brother.

Re: With four people, I can't get it up.
 

More common is ventilation, than cavitation. Ventilation is when air gets sucked down to the prop and causes it to slip and as a result revs the motor higher than it was before. Cavitation is when there is so much backward pressure on the water due to the blades spinning that it creates a vacuum in front of the blade.

Unless you hear and feel grinding/clunking, there's no way for "slippage" in the merc's lower unit (it is a merc, right, not a volvo?). All splines and toothed gears in there. If there was any slippage, you would feel it and get that painful feeling in your wallet.

Only places for slip are the coupler, the prop hub and prob blade to water.

Re: With four people, I can't get it up.
 

Here's the best way I can describe it:

If you set your drive position to half-way between fully down and fully up (not the trailer position, but halfway between the normal full "up" and "down" positions) and hit the throttle, you'll get the same result -- lots of RPMs, lots of wake backwash, rising bow, and maybe a 50/50 chance of getting on plane.

Re: With four people, I can't get it up.
 

Thank you -- that is awesome information. (And it makes sense.) I think I can safely eliminate the last two.

So... is the coupler something that can slip intermittently? Or under heavier load? Can it be fine one day and slipping the next? Or is it a symptom that once it develops, is always present?

Re: With four people, I can't get it up.
 

And watching the tach, the rpm's are definitely increasing when it won't get on plane? That sure sounds like it's ventilating. Different shaped props will cause that on startup vs turning vs trimming up. It sounds like your blade doesn't have enough cupping in it, but everything I read about that prop seems to say it will work fine for your setup.

Re: With four people, I can't get it up.
 

Correct -- RPMs start to jump at the very apex of the load on the engine -- just at the moment you'd expect the boat to level off. With the 21p, it would shoot up to 8000RPM very quickly. With the 19p, it's more gradual, but within 5 seconds or so, it's clear that you have to back off the throttle or it will redline.

Would either ventilation or cavitation be caused by a combination of different weight conditions AND water conditions? (ie., seaweed)? Or would these things ALWAYS be present, regardless?

Re: With four people, I can't get it up.
 

Once it slips, it will get progressively worse. It's a lot like the rubber hub in the prop, a rubber part pressed into a metal part. It's purpose is to separate a the outdrive from the motor. This will save your motor in the event that the gearset or something in the outdrive locks up.

Here's a pic of one so you get a better idea.
http://cgi.ebay.com/ebaymotors/Mercr...QQcmdZViewItem

But I suppose, if it only slipped a little bit, not enough to start smoking, it might work ok until you really got on it. When it runs right, is the motor and engine bay cold? When it slips is it hot? or vice versa?

Re: With four people, I can't get it up.
 

When the problem happens, there's nothing obviously burning, smoking, smelling, etc. I wonder, though, if the drive coupler IS slipping, but I'm backing off the throttle soon enough to prevent it from showing any signs.

I'll hit it pretty hard over the next few days and see what happens. I guess I agree with the service techs... it's either a clump of seaweed in the wrong place, or whatever it is will get worse and reveal itself.