Boat lost power to prop and revved while on the water.

[txmdc]

Like the title says, I took my new-to-me 1987 Thundercraft with a 4.3L V6 out to Lake Waco and our way back the engine revved up and the boat came to a screeching stop (figuratively of course). The motor runs fine but I have no power when I tried to shift back into drive or reverse. With the boat off and in drive, the prop spins freely both directions. I can hear the gears in the lower unit turning (not loud, just present) when I turn the prop.

Last night before I took the boat out, I changed the lower unit gear oil. It did not have water in it and the old oil looked ok. I filled it all the way back up with fresh oil.

What happened? More importantly, how easy/cheap is this going to be to fix? This is my first boat, but I have always been able to fix anything with a piston or a gear. If anybody has schematics to what the potential problem is, that'd help me a lot.

Thanks!
Andrew

 

[paultjohnson]

Re: Boat lost power to prop and revved while on the water.

Hi Thunder craft owner I run A 86 TC legacy Sounds like you spun the propshaft or the engine coupler. I replaced my engine coupler when I bought the boat in 1990 Engine had to be pulled It bolts to the flywheel and the driveshaft on the outdrive slides into it the coupler splines are aluminuminum and wear out about 400 PARTS AND LABOR THEN or its the prop hub less then a hundo

 

[txmdc]

Re: Boat lost power to prop and revved while on the water.

Thanks for your quick reply. Being that the prop hub is cheaper, and sounds like it's easier to check, how can I confirm it's not that? The gear sounds (not abnormal sounds) I hear when I rotate the prop with the gearshift in drive sounds like it's making good contact in the lower unit.

With that in mind, is it safe to assume the prop hub isn't my problem? How long would it take for me to change the engine coupler myself? I have an engine lift. Do I need anything else special? Is there a free manual I can get online?

 

[paultjohnson]

Re: Boat lost power to prop and revved while on the water.

does the prop spin at all when you go thru the gears with the engine running ?

 

[paultjohnson]

Re: Boat lost power to prop and revved while on the water.

If you can spin the prop with it gear Freely -with gearshift in FWD sounds like its in nuetral In FWD prop should lock up if spun CCW and ratchet if spun CCW opposite in REV If Drive shaft going into back of engine [coupler] isnt turning with engine running in any gear or nuetral, then its fhe coupler Look behind engine ftom inside of boat with engine running and checkBE SAFE!!!! If it is spinning and you cant get vthe prop to turn then you prob have a lower shift cable issue another post!

 

[Alpheus]

Re: Boat lost power to prop and revved while on the water.

Did you see or smell smoke? Did you smell any burning rubber? Stick your hand back into where the driveshaft goes into the coupler. If your fingers turn black and smell of burnt rubber, you need a new coupler.

As for he prop. Take the prop off and look at the hub for damage. You can also take the prop into a prop shop and have them torque test it.

Drain the oil in your outdrive and look for metal shavings.

I went through the same thing you did. Turned out I was just stuck in the mud...

http://forums.iboats.com/showthread.php?t=415879

 

[txmdc]

Re: Boat lost power to prop and revved while on the water.

I checked what I assume is the coupler at the back of the engine just before the transom. The shaft turns with the engine. Still no movement of the prop in fwd or reverse. I'm about to go take the prop off and see what I find. It does seem to have a tiny bit more vibration when I'm trying to put it in gear compared to when I'm revving it up in neutral. I did not smell any burning rubber when it all happened and I was in about 45 - 50 ft of water at the time.

It just all of a sudden stopped accelerating and revved up when this all started. The embarrassing part was I had to call the FD to bring a boat out and pull me back. There weren't any professional tow boats and I couldn't get in contact with the Game Warden. The worst part of it is that I'm a paramedic in the city. See why it was embarrassing?!?

 

[dingdongs]

Re: Boat lost power to prop and revved while on the water.

whilst on the muffs is it pumping water around the engine.does not have to be in gear to do this?
may not have any teeth left on upper gears.
pop cap off & have a look at upper gears
verticle shaft may have lost upper splines as another guy in the last couple of days.check by pulling lower

 

[paultjohnson]

Re: Boat lost power to prop and revved while on the water.

Thats a good indication thats its not the coupler now I would start thinking lower shift cable.. You might want to try disconnecting the lower shift cable at the engine and manually try to engage the gears. On the starboard side of the carb there is a plate where the throttle cable actuates the shift cable [shift cable is the lower one of the two that goes down thru the transom and works the shift lever in the drive] Take the nut off and remove the wire that holds the brass barrell in, pull it out and work it by hand. Pushing in on the cable should put the boat in FWD Push in and spin the propCCW prop should lock up and ratchet if spun CW.. Then PULL on cable and spin prop CW [putting it in reverse] Spin prop CW it should lock up and if spun ccw it should ratchet. If that works you may just need to adjust cable. If it still doesnt go into gear Trim your drive up a little so you can see up in front of the lower unit on the drive Get on you back and find the shift shaft that comes out of your lower unit . Its the little brass foot in the front of the drive. In fwd, Shift cable pushed in that little brass foot shoulb be pointing dead straight ahead . Then pull on cable a little bit , it should move cable to about the 1100 position as looking down from above thats nuetral then PULL on the cable and foot on shift shaft should be at about the 1000 position. Thats rev. Test by spinning prop as prev mentioned. If pushing/pulling on the cable from the engine doessnt move the shift shaft into the gears you need a new lower shift cable. If the cable doesnt move the shift lever Move the shift lever by hand with a screwdriver from under the boat You should be able to get your drive to go thru the gears that way If you cant... you may have lower unit issues Follow?....

 

[paultjohnson]

Re: Boat lost power to prop and revved while on the water.

xcellant thought by ding dongs totally didnt think about that option

 

[txmdc]

Re: Boat lost power to prop and revved while on the water.

Well the next promotion goes to DingDongs (though big thanks to everyone else too). Check out the photos and that'll tell you everything. With the boat in FWD turning the prop turns the lower gear. With it in N it does nothing. With all that being the case, it seems like everything else both below and aft seem to be working properly (at the moment).

Now for the next question... How do I best replace these? What are they even called? Please forgive my boat ignorance, but I've been a boat owner for less than a week (the yak doesn't count!) and this is all new to me. This seems like a repair that should be done at home and not at a dealer (though most people wouldn't change a car motor or transmission themselves I suppose). Where is the best and/or cheapest place to get them?

Thanks guys!

 

[txmdc]

Re: Boat lost power to prop and revved while on the water.

Also, is this caused by normal wear and tear, abuse, or possibly both? How can I prevent this from happening again?

 

[Fishermark]

Re: Boat lost power to prop and revved while on the water.

Probably time to identify what you are working on. Then we can better give suggestions on where to go from here.

 

[jerryjerry05]

Re: Boat lost power to prop and revved while on the water.

Looks like a NO oil or low oil situation.On e-bay look for Mercruiser Sterndrives and you can find almost anything you need.If you have $$$$ you can get a rebuilt unit from Jasper or even this site.
When you reinstall make sure you put in a resivoir for the gear oil.It's a tell tale that lets you know if there is a problem and it won't cost as much next time.J

 

[Eric 3.7LX Alpha 1]

Re: Boat lost power to prop and revved while on the water.

The 4.3's came with a 1.84 ratio in the drive which are those upper gears that are toast.

There should also be the letter "D" stamped on the universal joint splined yoke which would also indicate 1.84:1 ratio.
Good Luck

 

[txmdc]

Re: Boat lost power to prop and revved while on the water.

In response to what we're working with... Its a cobra sterndrive, OMC 4.3L, 19' Thunder Craft cuddie.

Someone mentioned searching for mercrusiser parts... Will they interchange? Also I have access to a volvo SX sterndrive from a 94 connected to a 4 cyl volvo engine. The sterndrive was repaired and never put in the water. Any chance I could make that one work for me? If not, are these gears just called the upper unit gears?

 

[txmdc]

Re: Boat lost power to prop and revved while on the water.

So how does one go about changing these gears? Does anybody have used ones laying around? They're pretty d@~% expensive!

 

[Alpheus]

Re: Boat lost power to prop and revved while on the water.

You might want to try ebay, or do a search on craigslist for "project" or "TLC" adds for a parts boat...

 

[dingdongs]

Re: Boat lost power to prop and revved while on the water.

sorry to hear u found the problem.you now have to weigh up if your 23yr old boat is worth splashing out big bucks on.you have the advantage of being in the states and a company here;http://www.sterndrive.cc/mm5/merchant.mvc? will give a 3 year warranty too.$1395+$350 for the cobra conversion.chance is if your engine,hull and trailer were good may well be worth getting back on the water.

 

[txmdc]

Re: Boat lost power to prop and revved while on the water.

How do you guys feel about a used upper unit off ebay? approx $400 shipped is the best I found for one that wasn't worn out. I'm thinking that is my best option, but I'd like other's input.

I also am interested in learning about the volvo pinta SX swap, but I don't know if one from a 4 cyl volvo would be ok on my v6.