Slippage under load

[boardrider]

My wife and I just bought our first boat and are trying to work out the issues regarding a slipping problem on our Mercruiser Alpha I/O (boat is 1984 Wellcraft Nova, new engine 2001). I will give you the short story. Boat is slipping when it is under load, like when it is trying to plane out. From research, I learned it is probably the prop hub, or engine coupler. This is before we got the boat out of the water (been in mooring for a couple years.) <br /><br />We put a different prop on and it still had the same problem, so I don't think it is that. I looked in the engine compartment at the coupler area and observed no rubber schrapnel or anything. <br /><br />Once the boat was pulled, we discovered a large chunk missing from the lower part of the outdrive (broken off.)<br />See these pics<br /><br /> http://pg.photos.yahoo.com/ph/dkpop...=&.done=http://photos.yahoo.com/ph//my_photos <br /><br />I know this is not good, but I am wondering if this could be the culprit of the slipping problem. My guess is "yes." I really don't know crap about boats though. Is there gear oil held in there? Could the penetration of water in that area cause problems with the gearing etc. leading to the cause of my problem?<br /><br />The problem only occurs under heavy load either when I give full throttle, or it is trying to plane out. When you back off from the throttle, it will catch and engage again under low pressure, but not in a consistent manner.<br /><br />All thoughts and suggestions greatly appreciated, as I am a NEWBIE. Thank you very much in advance.

 

[Haut Medoc]

Re: Slippage under load

Unless you are overheating, your problem is not the coupler.....Once the coupler is shot ....It's shot..Same with the drive itself...There is no slipping......Your pick doesn't show up here, so I can't help with the chunk missing thing until I get a pic I can view.....What kind of prop. are you running? It sounds like you may be cavitating.....JK

 

[mike11374]

Re: Slippage under load

what does cavitating mean?

 

[Dunaruna]

Re: Slippage under load

Cavitating is when water boils at the prop - google it for more details.<br /><br />Medoc mean't 'ventilate' (right medoc?).<br />That when air is sucked down to the prop, causing the prop to loose it's grip - it slips.<br /><br />Your link is not linking.

 

[boardrider]

Re: Slippage under load

Try the link again, I changed permissions.<br /><br />I used the prop the boat came with:<br />14", pitch 17 and then a 14.5", pitch 17 - <br /><br />both I believe are stainless steel 3 blade. Not that I have experienced what cavitation is (air pockets in the rotation area right?), but I don't think it is that considering it did it with two separate props. If it is cavitation, could that be caused by something besides the prop ie. the chunk out of my outdrive creating an airpocket?

 

[Dunaruna]

Re: Slippage under load

Forget about cavitation, you have much more serious problems to worry about.<br /><br />I'll let others more qualified to answer your questions, but I suspect your leg is toast.

 

[boardrider]

Re: Slippage under load

Really - that would be a bummer! I was just conversing with a colleague and we came up with the hypothesis that indeed it could be cavitation from the exhaust getting trapped in the broken area and released into the rotation of the propeller - causing the slippage. This is a possibility right?<br /><br />It makes the most sense to me at this point. Regardless, minimally I will need to replace the lower outdrive housing. <br /><br />I am trying to get one of 2 unwanted alpha units to bolt on as a whole piece (upper and lower) due to the fact that the entire unit is corroded as he11.<br /><br />So what else can cause the slippage besides the following?<br /><br />Cavitation<br />Engine Coupler (pretty much ruled out)<br />Prop Hub (ruled out)

 

[TilliamWe]

Re: Slippage under load

Oh my that drive is damaged! I don't see how you have any gear lube in it at all. At the very least you need a replacement lower unit housing & the drive needs to be gone through & checked for damage. But that can't be good at all. Be prepared to buy a whole replacement outdrive!

 

[Northern Eclipse]

Re: Slippage under load

I'm surprised that boat even moves with a large section of the gear case missing, that drive cannot have any oil, and saltwater damage must be large time for a new or rebuilt leg, that one is finished. I would also suggest you get a manual and learn more about your boat and when and how often you need to service it... 2 years in a wet mooring is a neglected boat.

 

[boardrider]

Re: Slippage under load

Thanks everyone for your time and responses. This is a dumb ? <br /><br />What is the "leg" of the drive? The lower part of the outdrive?<br /><br />There has been an abandoned boat here at my office behind the wharehouse that belonged to a former owner of the company. It has an outdrive in great condition I am trying to get my hands on for a complete replacement - hopefully cheap. The thing has been here over 6 months and now is starting to be vandalized (tires taken off trailer.)<br /><br />I've been trying to source a manual for the boat, but came up short.

 

[Haut Medoc]

Re: Slippage under load

Holy sh!t, batman You have issues....."Drive" & "Leg" are the same thing....Those of British persuasion refer to it as a "leg"....Since you are in the U.S., I will call it a drive.....Your drive is shot, btw..... ....Frankly, I'm amazed that the boat moved at all...You are probably going to need more than just a new drive, but that is a good place to start.....You need to find out exactly what engine/drive you have ....Post your serial #...That will help with getting you to the right manual.. ....Should be on the engine.....You will need a drive with the proper ratio for your specific engine......The fact that it actually runs is a good thing.....And it is a Mercruiser not an O.M.C., so you've got that going for you ... You are in the right place....Looking in the 'search' function at the top of the page will yield a plethora of information.....BTW, if it freezes by you, it is time to think about winterizing.....JK

 

[Bondo]

Re: Slippage under load

boardrider<br /><br /> Wander over Here,............ It's a Good Basic Info place,.........<br />That way You'll Know what We're Talking about,..............<br /><br />By the look of the picture,........<br />You Don't Have an Outdrive,......... I Too Can Not Believe that the boat Moves,... At All............<br /><br /><br />

<br /><br /><br />You Need a Complete Outdrive,...... Upper,+ Lower Units,.... All of It.........<br /><br />I Don't see ANY Salvage in that photo.............Just Scrap Metal............<br /><br />Sorry,.......... And Good Luck............

 

[boardrider]

Re: Slippage under load

To all of your suprise, the thing actually planed out this weekend and was cruising during our test - not long and not consistently. I have accepted now that the whole thing needs replacement. Just don't know how to break it to the wife.I didn't think it was that bad, but I guess that really shows you what I know - didly squat. That's why I am here and again I appreciate the help! Though it's not what I wanted to hear <br /><br />Sweet link Bondo great info!

 

[Weirdwalt]

Re: Slippage under load

Thats the exhaust coming out of that hole. That will cause cavitation problems. I say first, fix the leg, and then we'll figure out why it wont plane. I'm bettting a power problem.

 

[Don S]

Re: Slippage under load

Yep, thats the exhaust section of the drive and with the exhaust pushing out the side through that hole, it puts air bubbles right at the base of the prop blads. Cavitation will be a VERY big problem.<br />The problem appears to be from corrosion which is common when the anodes on the drive and transom shield never get replaced, or there is stray electrical current in the water around your boat, or from your boat (Check your wiring).<br />The other problem is the drive is not the only thing being corroded away. The transom shield (That thing between the inside and outside of the boat) is also corroded, along with the trim cylinders and anything else metal in the water.<br />At this point and seeing you have little experience, before you end up sinking the boat, take it to a "REAL" Mercruiser dealer and have them look at it.<br />Personally I wouldn't even get into the boat if it was sitting in the water.

 

[boardrider]

Re: Slippage under load

The outdrive I am looking at looks exactly like mine (Alpha One), but it is from a 228 and mine is a 260. This would still match up and swap onto mine right? The gear ratio on the used unit I am looking at says 1.50. I have no idea what mine is because of the corrosion, but from what I have read online, it should be the same 1.50R in my boat.

 

[Haut Medoc]

Re: Slippage under load

If you have an 8 cylinder engine, 1:50 is perfect.... However if it says "888" on it, then 260 H.P. is too much for that drive....JK

 

[boardrider]

Re: Slippage under load

SWEET! I've got a 350.

 

[TilliamWe]

Re: Slippage under load

should be what you need.

 

[Bondo]

Re: Slippage under load

However if it says "888" on it, then 260 H.P. is too much for that drive....JK

OK, JK,...............<br /><br />Educate Me,.................<br /><br />What,... Exactly Are the Differences between the 888,+ the Model 1,.. Pre Alpha that was put behind the 350, 260hp motors up Until 1983..???...............