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Author Topic:   1994 21 outrage low speed vibration

Tail Chaser posted 05-25-2013 01:03 PM ET (US)
i Own 1994 21 outrage with tee top, 1999 efi 225 Merc , went for a ride the other day , notice bad vibration at low speed. Boat at idle is smooth , loud but smooth, will do 52 mph @ 5600 RPM, NO LACK OF POWER , TEMP is 130- 140 no alarm , prop is fine , Sei lower unit ( new)--any thoughts? Motor is mounted second-hole-up? Has anyone experienced the hull shaking? Low speeds. I believe there is water in the hull.
Buckda posted 06-02-2013 10:16 AM ET (US)
I don't believe that water in the hull will cause vibration.
On some engines, there is a transition point of rough running that you must push through as the boat climbs on plane.
Without more information it is very hard to help.
Are you certain the prop is fine? That would be my first suspect. Since you don't have carbs, that eliminates my second suspect.
Finally, you have a "new" rebuilt lower. I would have my mechanic check that and check my warranty very carefully. They have a pretty good reputation, but could be something wrong. You want to get it resolved within the warranty period or at least eliminate it as a suspect within that period.
EaglesPDX posted 06-02-2013 11:24 AM ET (US)
You can check for water in the hull by weighing the boat. If trailering, use the public scale on the road. If mooring, most of the haul out rigs tell weight.
I was concerned about water in an old hull as the fuel tank cavity foam was saturated, but the weight numbers came out right and that gave me some assurance of no water.
I don't think water in the hull would cause a vibration though, that's always going to be due to motor and propeller.
jimh posted 06-02-2013 11:39 AM ET (US)
See
http://continuouswave.com/whaler/reference/FAQ/#Q3
jimh posted 06-02-2013 11:44 AM ET (US)
The laminates used in Boston Whaler boats are not particularly thick and strong, and much of the strength of the hull is obtained from the bonding of the laminates to the Unibond hull foam interior. If the bonds between the hull laminates and the foam interior are compromised, the strength of the hull would decrease and the rigidity would decrease. This could lead to the hull flexing.
I am not certain what is precisely meant by shaking. It would be unusual for a Boston Whaler boat hull to vibrate with enough displacement of motion that you could describe the hull as shaking. Usually vibration is limited to some other structure attached to the hull, like the railings or a radio mast, which can be driven into vibration. A hull that is so weak and flexible it can be driven into a vibration motion is probably not a very sound structure, or, it is being excited by a very strong vibration force.
jimh posted 06-02-2013 01:09 PM ET (US)
[Combined three concurrent discussions on this boat into one.]
Jerry Townsend posted 06-02-2013 04:23 PM ET (US)
Your vibration is caused by an unbalance/misfiring of your engine. The hull cannot cause vibration.
Recheck the prop - but at the low speeds, I suspect that it might be a cylinder that is misfiring. Might also recheck the lower unit, but it would take a large unbalnce within the lower unit to cause a vibration. ---- Jerry/Idaho

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Author	Topic: 1994 21 outrage low speed vibration
Tail Chaser	posted 05-25-2013 01:03 PM ET (US) i Own 1994 21 outrage with tee top, 1999 efi 225 Merc , went for a ride the other day , notice bad vibration at low speed. Boat at idle is smooth , loud but smooth, will do 52 mph @ 5600 RPM, NO LACK OF POWER , TEMP is 130- 140 no alarm , prop is fine , Sei lower unit ( new)--any thoughts? Motor is mounted second-hole-up? Has anyone experienced the hull shaking? Low speeds. I believe there is water in the hull.
Buckda	posted 06-02-2013 10:16 AM ET (US) I don't believe that water in the hull will cause vibration. On some engines, there is a transition point of rough running that you must push through as the boat climbs on plane. Without more information it is very hard to help. Are you certain the prop is fine? That would be my first suspect. Since you don't have carbs, that eliminates my second suspect. Finally, you have a "new" rebuilt lower. I would have my mechanic check that and check my warranty very carefully. They have a pretty good reputation, but could be something wrong. You want to get it resolved within the warranty period or at least eliminate it as a suspect within that period.
EaglesPDX	posted 06-02-2013 11:24 AM ET (US) You can check for water in the hull by weighing the boat. If trailering, use the public scale on the road. If mooring, most of the haul out rigs tell weight. I was concerned about water in an old hull as the fuel tank cavity foam was saturated, but the weight numbers came out right and that gave me some assurance of no water. I don't think water in the hull would cause a vibration though, that's always going to be due to motor and propeller.
jimh	posted 06-02-2013 11:39 AM ET (US) See http://continuouswave.com/whaler/reference/FAQ/#Q3
jimh	posted 06-02-2013 11:44 AM ET (US) The laminates used in Boston Whaler boats are not particularly thick and strong, and much of the strength of the hull is obtained from the bonding of the laminates to the Unibond hull foam interior. If the bonds between the hull laminates and the foam interior are compromised, the strength of the hull would decrease and the rigidity would decrease. This could lead to the hull flexing. I am not certain what is precisely meant by shaking. It would be unusual for a Boston Whaler boat hull to vibrate with enough displacement of motion that you could describe the hull as shaking. Usually vibration is limited to some other structure attached to the hull, like the railings or a radio mast, which can be driven into vibration. A hull that is so weak and flexible it can be driven into a vibration motion is probably not a very sound structure, or, it is being excited by a very strong vibration force.
jimh	posted 06-02-2013 01:09 PM ET (US) [Combined three concurrent discussions on this boat into one.]
Jerry Townsend	posted 06-02-2013 04:23 PM ET (US) Your vibration is caused by an unbalance/misfiring of your engine. The hull cannot cause vibration. Recheck the prop - but at the low speeds, I suspect that it might be a cylinder that is misfiring. Might also recheck the lower unit, but it would take a large unbalnce within the lower unit to cause a vibration. ---- Jerry/Idaho