New boat symptom, thoughts?

[Wakeboarder3780]

I filled up the ballasts for the first time this season and noticed something different when driving. It started when I was hauling around a tight corner. I thought it was just cavitation at first. Then it happened when I was going straight and picking someone up.

It kind of sounds and feels like cavitation. Basically the engine spins but you don't get any force pushing you forward for just a bit. Then you get the power back again. I'm hoping it isn't a transmission problem, but I guess it is a 20 year old boat.

If it matters its an 89 malibu sunsetter. Thoughts?

[pet575]

Sounds like propeller ventilation or something similar. Have you had the prop checked lately?

[Okie Boarder]

Is it only happening when you carry the extra weight? Have you tried opening the engine compartment and looking at the shaft to see if it is engaged and spinning when this happens?

[BrianABE]

My old 88 Correct Craft did this one time only when turning (if it's the same thing). There is a bearing with a little bolt through it around the shaft right before it goes through the hull. On a old CC there is a black round cover in the floor behind the motor. It may need to be tightened down a little bit... but not to much. They are designed to leak a little bit of water to keep the shaft lubed. Check and make sure that isn't too loose because if it is that will give you the same effect as if it were cavitating.

[Wakeboarder3780]

yeah it's only happening with the extra weight on a hard throttle. We took 2 less people out so a little less weight and I told the wife to take it easy on the throttle and she didn't hear it act up. I was reading a bit online today and I heard things like low transmission fluid could do it. I check the fluid and it is a tad low. Then again I only ran it for 5 minutes so maybe it wasn't hot enough.

I'm trying to figure out the proper transmission fluid for it but google fails me. I'll probably call malibu tomorrow and see what they say about fluid. That's cheap and easy for me to replace so i probably will. Is it normal for it to be a bit bubbly on the dip stick if you check it right after running it?

I'm hoping the little bit of bubbly doesnt mean water in the fluid.. I know frothy can mean there is water in it but a few bubbles?

[Enygma]

I would have just assumed it would be gear oil. But I dunno, Haven't done much work on boats. It does sound like something is slipping and you may be on the right track with thinking it wasn't warm enough.

I usually do a good run down the lake and and let the boat idle a bit before giving the first pull.

[Wakeboarder3780]

I'm going to replace the transmission fluid tomorrow and I'll let you guys know if I see it crop up again. Not sure how to change the oil in the transmission if it comes to that..

[ryan351w]

These type of drives only hold about 2qts or so, so even if its a half a qt low it will effect the performance.
Corners can make a big difference because the fluid sloshes to one side. And heavy ballast will also cause the same issue.
I know velvet drives do not use gear oil. They typically use Dextron/Mercon III std GM auto trans fluid. The gear oil is just too heavy. You can easily tell whats in it, if its red its std ATF, if it stinks and looks more like engine oil its gear oil.
I would add enough to bring it up to full and see what happens.

[Wakeboarder3780]

oh my bad, from the posts I was assuming there was transmission fluid and oil in a different compartment. I'm guessing from your response, ryan, that isn't the case, it's just one or the other?

[ryan351w]

Wakeboarder3780, Well um huh? Sorry I may not have been clear, what I was saying is that these drives use automatic trans fluid, not gear oil.

[Enygma]

yeah, dont listen to me wakeboarder. I haven't done a lot of work on boats and don't really know. I have done a lot on cars but if Ryan say transmission fluid then go with that.

[Wakeboarder3780]

hey guys, sucked out all the old fluid and replaced with the new fluid tonight and then took her out for a spin. We were nice to it and didn't notice anything. I think this was a case of low fluid for 2 reasons.

When I was doing diagnostics the first time..
1) When I checked the fluid after running it for 5 minutes it was low.
2) When I checked the fluid I waited WAY too long after shutting the engine off to check it. You literally need to check it right after the engine shuts off before the fluid has a chance to drain from the lines back into the reservoir. So since the fluid was low even AFTER I let the fluid drain from the lines back into the reservoir I must have been substantially low.

I sucked out all the old fluid and filled it up with new fluid to the full line cold. Since I figured I'd need to add more (lines need to get filled up) I brought out an extra quart with me. I had the Mrs drive and we warmed it up for 5 minutes and then brought it down to idle.

I opened the hood and got ready to pull the dipstick. When I said stop she shifted to neutral and cut the motor, I immediately pulled the dipstick, wiped it, stuffed it back in and withdrew it. After running it it had gone down a couple hash marks. Tossed about 1/5 of a quart at it and tested a few more times to get it right and it's now full when hot IMMEDIATELY after shutting the engine off.

Next time we're out I'm going to load the piss out of it and have her really throw the throttle down hard every time and make sure it's behaving, but I'm pretty sure this one is solved.

The velvet drive I have takes Dexron II ATF (any number above II is "backwards compatible"). 2 quarts of ATF might be the cheapest boat fix I've ever done

[ryan351w]