Sudden vibration/loss of power/then ok!

[tinnchris]

HI! I have a 2001 21i. This weekend we are running great, then suddenly while pulling someone There is a pretty significant vibration and loss of power. Then it just went away! This happened a few times throughout the day and I noticed that if I stopped put it in reverse and then started forward again it would go away. Toward the end of the day the vibration was much less noticable, but there...and the power was still lacking. I checked the prop and there isn't a ding on it. It also seems to spin pretty freely. Anyone else experience this? Would love some advice on things to check! Thanks!

[Tige M.D.]

check the trans fluid level, color and smell.

[tinnchris]

I know, I know...not exactly an engine expert here...What should the color and smell be? Thanks!

[Tige M.D.]

fluid should be light red and smell sweet.

[Paul Robertson]

Don't mess around with the fluid. Make sure you get it completly checked out!!!

Had a similar problem with our 20i 315Merc. We had a number problems with the engine - injection system, electrical. Finally had it running well and had the same thing happen. We're up in Canada and had family in from the West coast and the vibration started half day in.

Spoke to the dealer - check the fluid level, fishing line, prop damage. OK to all. Finally took it in and turns out the tranny is pooched. But that never happens. So after 6 weeks off the water they finish arguing warranty and rebuild, (I'd demanded new).

That was 2003. Summer 2004 it starts doing the same thing. I check the fluid level and even though it reads on the stick as 1/4 the way down the 'operating range' the fluid needs to be topped up to eliminate the vibration - Don't trust the dip stick! Keep it topped up.

The dealer is currently trying to locate the leak.

I would really like to hear from Tige on this issue. Apart from the engine this is one heck of a boat.

[Tige M.D.]

paul,
i know where the leak could be. we saw dozens of velvet drives fail from a leak in the shift spool. there is an o-ring that was failing. the leak would only happen while in gear and under a load. it would take about 5 minutes to start leaking. have the dealer put the boat in the water and test it in real world conditions, not a test tank.

never over fill your transmission and trust the dipstick, thats why it is there. the dipstick needs to be pushed/threaded all the way down and checked immediatly after shutting down the engine.

too much fluid WILL burn up a transmission as fast as too little fluid.

[Tip]

Greg,
Speaking of transmission fluid, what type of fluid do you use in a velvet drive? They used to have two different types of transmission fluid (Type F was for Fords), do they still have more than one type or is there just one type now?

Tip

[Tige M.D.]

tip, we use dextron III ATF. it is the GM fluid. the system will take about 1 1/2 qts.

[Flying Tiger]

I've found the problem is when I have water in my bilge.
Sometimes the bilgepump has to run an manual.

[Tige M.D.]

so, what your saying is, water in your bilge causes your boat to lose power and vibrate?

[CiceroJoe]

My boat has a mild top end loss of speed, very mild vibration, and
has a whining noise that can only be compared to a pneumatic impact wrench when youre pulling the trigger and not torquing down a nut. That "wheeoouughh" sound. Sounds nuts huh? That sound is very light, but noticable and coincides with the time the other symptoms started. Velvet drive seems full, and it has a brand new acme 4-blade.
When I first put it on I was getting 41-42mph, now getting 36-37mph avg. Prop is symmetric and still perfect.

Drive shaft?
Velvet Drive?

I just dont know. Any ideas?

[GIZMO]

Does the noise only occur at one speed then go away? I had a similar type noise start at about 500rpm then go away at 1000 rpm. It started when I had the prop replaced with a new one. Tige M.D. said it could be the new prop.
I had the old prop repaired but have not tried it yet.

GIZMO

[CiceroJoe]

It ran beautifully for a couple weeks with the new acme, 4-5 2hr uses, then that sound started happening. It doesnt do it until you run it around 13-15mph thru 36-37mph progressively louder as it accelerates.

WTF.

[GIZMO]

Does not sound like the same noise I have. One other thing to check is your tracking fins. If all three are lined up perfectly it causes them to vibrate. Take a mallet and tweek the center fin out. I ran over a sand bar and knocked them into perfect alignment. The faster I went the louder it got, smacking the center fin around a little fixed it.

GIZMO

[CiceroJoe]

You have got to be joking!!! If that helps irregular sound/vibration why would they make them perfectly aligned at the factory?

However, to be honest with you, the fin thing was my next suspect though. My rear fin I believe is probably 5 degrees off center. Like it hit something and was bent. I thought that could be the culprit, but you make it sound like I need to whack them out of alignment more to get rid of the sound/vibration?

How did you know to off center that center tracking fin??

If you got shallow enough to hit a sandbar and somehow align your tracking fins, I am afraid to ask what it did to your drive shaft and prop blade!! At that point I'm sure a little vibration/noise was your last worry.

:confused:

[GIZMO]

When we hit the sand bar it also bent the prop. The dealer took care of the prop. Then I described the noise to them and they contacted the facyory. They told us the center fin should be slightly out of alignment.
If it's not the front fin causes the center fin to cavitate and vibrate. (thats the way I understood it I could be wrong) but if your rear fin is bent that is definitly a good place to go next. Just tweek it a little and see if the noise changes.

GIZMO

[Tige M.D.]

you might want to have a fuel psi test done. the fuel pump will start screaming at you when it gets tired. this could also have to do with your loss of power.

the acme prop will change your top speed of your boat. what i need to know is, did the wide open throttle (wot) change?

i have never heard of the bent fin theory? i am going to call and check on this. maybe i will learn something new:)

[CiceroJoe]

I went from a 3 blade to a four blade acme. When the three blade was on there the rev limiter was activating and the top end was around 33-34 mph. Now the hole shot is slightly boggier but top end goes to 42 mph. But now that I started hearing that whine I described in an earlier post with more detail, top end is 37mph. The boat is a 2002. Tige MD, you think a new fuel pump would cause this noise and be suspect after only two seasons?? I'm looking into the prop alignment issue this saturday at the pole barn where its at. I gotta see this.

Those fins are pretty stout and beefy, should take a hell of a whack with a mallot to angle them off center.

GIZMO, did the dealer/factory tell you what angle for the center fin???

[CiceroJoe]

boat pic

[CiceroJoe]

Thinking about putting on WCG...

Think it would look good?

[CiceroJoe]

Here's mine

[Tige M.D.]

we ave to use a 4 ton porta-power to move a fin. good luck using a mallet.

mercruiser fuel pumps are very susceptible to failure if the fuel gets old and sticky or there is too much resistance (vacuum) before the pump ie. clogged pre-filter. the fuel pump uses recirculated fuel to cool itself, if the is a lack of recirc'd fuel or the pumps ports are clogged the it will get hot and start screaming. just have someone do a fuel psi test should be between 32-36 psi with the regulator disconnected from the engine vacuum. this will simulate full throttle.

[CiceroJoe]

No mallot. Gotcha. I'll check into the fuel pump issue.

Thanks Tige M.D.

Got 2 new fat saks for the boat for this summer, along w/some fusion speakers..