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View Full Version : Engine violently shakes and vibrates - won't accelerate


djbartu
09-15-2008, 01:14 PM
I've searched this forum quite a bit and have found similar problems to mine, but none are really what I am experiencing. Here's the story:

Yesterday, my engine really started vibrating under load. The boat was running fine as I pulled my kids tubing for about an hour. Then as my wife attempted to ski, I hit the throttle and the whole boat just started vibrating and shaking. I immediately pulled the throttle back up and the engine stalled. It started right back up and idled smooth and quiet. It revved up effortlessly as it always did. Oil pressure was good and the temp was normal. Even without a skier the boat would not accelerate. Not wanting to damage anything more, I then slowly took the boat back to the dock and parked it. I felt around the prop thinking maybe something was wrapped up, but everything seemed OK there also. The boat has a Velvet Drive transmission that was a rebuilt unit I installed about 2 years ago. The engine is an Indmar 351.

Any ideas as to what might be going on? I've read the posts on fuel pumps, but the engine doesn't stall out, it just shakes like crazy.

Thank you for any advice you may be able to give me,
Denis

Monte
09-15-2008, 01:15 PM
You may have water in the gas.

bcampbe7
09-15-2008, 01:58 PM
I've searched this forum quite a bit and have found similar problems to mine, but none are really what I am experiencing. Here's the story:

Yesterday, my engine really started vibrating under load. The boat was running fine as I pulled my kids tubing for about an hour. Then as my wife attempted to ski, I hit the throttle and the whole boat just started vibrating and shaking. I immediately pulled the throttle back up and the engine stalled. It started right back up and idled smooth and quiet. It revved up effortlessly as it always did. Oil pressure was good and the temp was normal. Even without a skier the boat would not accelerate. Not wanting to damage anything more, I then slowly took the boat back to the dock and parked it. I felt around the prop thinking maybe something was wrapped up, but everything seemed OK there also. The boat has a Velvet Drive transmission that was a rebuilt unit I installed about 2 years ago. The engine is an Indmar 351.

Any ideas as to what might be going on? I've read the posts on fuel pumps, but the engine doesn't stall out, it just shakes like crazy.

Thank you for any advice you may be able to give me,
Denis


What year?

Could be a hell of a miss. I had a coil pack go out on my 04 Yukon and the whole truck shook under load (it idled fine).

djbartu
09-15-2008, 02:14 PM
OK, I will add some dry gas just to give that a try, but, I doubt it would be water in the gas due to the fact that the tank is over 1/4 full and the boat ran perfectly for over an hour before this "all of the sudden" problem.



Oh yeah, it's a 1986 ... Holley carb.

ttu
09-15-2008, 02:17 PM
could it possibly be a clogged fuel filter.

bigmac
09-15-2008, 02:29 PM
You say it idles fine and that the shaking occurs with acceleration or under load. Are you sure it's the engine? What does the prop/strut/shaft look like? My first thought would be something in the driveline rather than engine itself....

A dinged prop could certainly explain your symptoms, and it wouldn't take much of a ding to do it.

LakePirate
09-15-2008, 02:34 PM
My vote goes to drive shaft.

Hollywood
09-15-2008, 02:47 PM
Unless he hit something between tubing and skiingit should not be shaft/prop related. Sounds like the timing went WAY out. My stab is at the EI clunking out.

Maristar210
09-15-2008, 02:48 PM
Start the boat. Let it warm at idle. Put it in Neutral and rev. If it shakes then its motor related if it does not shake it is driveline related. Driveline would typically be a bent prop or shaft. That is my guess.

Sunken debris can cost you, I speak from experience.

Keep us posted !!!

Monte
09-15-2008, 02:51 PM
OK, I will add some dry gas just to give that a try, but, I doubt it would be water in the gas due to the fact that the tank is over 1/4 full and the boat ran perfectly for over an hour before this "all of the sudden" problem.



Oh yeah, it's a 1986 ... Holley carb.

My boat had the exact same feeling about a month ago. the only difference i can see is I could basically bury the throttle arm and run about 1/2. Luckly my neighbor is my mechanic, so I had him look at it. He rebuilt the carb, and seperated the gas from the water. If it is water in the gas your fuel seperator is full of water too. It was the exact same scenario. I was pulling the kids on tubes. His best guess is the water went in the fuel overflow as a result of hitting my own waves when I dropped throttle to go back, or the ballast from surfing the day before had me too low in the water. It had exatly a 1/4 tank in it when the boat started doing its thing. BTW mine was running fine for the 45 or so I was pulling my kids. 1986 here too

LakePirate
09-15-2008, 03:12 PM
My boat had the exact same feeling about a month ago. the only difference i can see is I could basically bury the throttle arm and run about 1/2. Luckly my neighbor is my mechanic, so I had him look at it. He rebuilt the carb, and seperated the gas from the water. If it is water in the gas your fuel seperator is full of water too. It was the exact same scenario. I was pulling the kids on tubes. His best guess is the water went in the fuel overflow as a result of hitting my own waves when I dropped throttle to go back, or the ballast from surfing the day before had me too low in the water. It had exatly a 1/4 tank in it when the boat started doing its thing. BTW mine was running fine for the 45 or so I was pulling my kids. 1986 here too

Liar .

Monte
09-15-2008, 03:13 PM
Liar .

Am not .

LakePirate
09-15-2008, 03:22 PM
Am not .


Sure .

:rolleyes:

DanC
09-15-2008, 03:27 PM
my engine really started vibrating under load...
It started right back up and idled smooth and quiet. It revved up effortlessly as it always did.

I had a guy at a boat ramp complaining about the same thing. I looked under his boat after he pulled out with the trailer. He had a 24"x10" piece of driftwood impalled across his front tracking fin.
One time I had similar symptoms. Underwater check of the prop seemed good. Out of the water check of the prop seemed good but upon moving the prop we saw one blade was way off. Must have hit a soft piece of drift wood, not a scratch or a ding in the prop but one blade was significantly bent compared to the others.

FrankSchwab
09-15-2008, 04:40 PM
After checking for logs impaled under the boat, a bent prop, bad gas, and a f*ed up ignition system, is to check for other damage in the driveline. Sheared bolts at the coupler, or a sheared shear pin in the prop could do something similar, and the failure mode would be what you saw - under acceleration.

boxman3
09-15-2008, 05:00 PM
Might be worth a look at the distributor, the older ones have springs with a weight for the advance... Spring(s) go bad, boat idles, no power or loss of power, then cut's off, then restarts fine.... Then the whole thing cycle starts over.... 86 Pro Star has points unless you have updated to electronic, which is a good thing!

TRBenj
09-15-2008, 05:19 PM
Might be worth a look at the distributor, the older ones have springs with a weight for the advance... Spring(s) go bad, boat idles, no power or loss of power, then cut's off, then restarts fine....
Thats where I would be looking too. If the plugs and wires are in good shape, then the first place I would look is in the base of the dist. My bet is a broken advance spring.

JimN
09-15-2008, 05:34 PM
Not knowing if the plugs, cap, rotor and wires are newer, they only last for so long and three years is about all I would expect out of them with normal running time. However, they can past much longer if the conditions are right.

Has this motor overheated? If it has, it's possible for the motor to run smoothly at idle and in neutral at higher RPM. Under load, it may act like it's on America Can Dance. A bad head gasket can cause this doe to the overheat, ot several overheats.

Look inside of the mufflers, too. If the flaps are blistered inside, it has overheated.

djbartu
09-15-2008, 08:41 PM
Hmmmm. I see there are quite a few possibilities. Tomorrow is a day off from work so I'll see what I can figure out.

By the way, when I "freshened up" the motor two years ago, the points were replaced with a Pertronix unit, with a matching coil and plug wires, plugs were replaced, and an Edelbrock aluminum intake was added.

The engine has never overheated or even ran close to too hot. The water pump did develop a drip at the beginning of the season last year, so the impeller was changed at that time.

Thanks everyone for the advice so far. I'll let you know what I find out.

JimN
09-15-2008, 08:54 PM
If you can check the compression, you'll be able to verify or rule out a head gasket leak.

djbartu
09-15-2008, 09:57 PM
If you can check the compression, you'll be able to verify or rule out a head gasket leak.

Thanks, I'll try checking the shaft/prop first, then fuel, timing, and dist. If I get nowhere with those, I'll also do a compression check.

Any chance something inside the tranny is messed up? As posted before it is a rebuilt unit from FFI.

bigmac
09-16-2008, 07:42 AM
The water pump did develop a drip at the beginning of the season last year, so the impeller was changed at that time.

A drip from the raw water pump means a bad seal - nothing to do with impeller.

djbartu
09-16-2008, 07:13 PM
And the winner is ... boxman3. He first mentioned the distributor advance springs.

Sure enough, they were quite rusted and one was broken.

Before I pick up a replacement set, do these springs have a different tension than stock Ford automobile/truck springs (e.g. '86 Ford F150)? Also, it seems that with the original springs one was heavier (thicker wire) than the other. With some aftermarket (Mr. Gasket) replacement sets I've seen online both springs are identical. Any idea where the best place to get a set would be? I'm thinking of heading to my local NAPA and seeing what they have.

Thanks everyone for your help!

boxman3
09-20-2008, 04:19 PM
I used Mallory parts in my rebuild years ago. I did my parts look up using a Ford Mustang for my year. Some folks would use skidim.com for parts.