Boat Question...

[Badchoices03]

Finally planning on pulling the boat out and do all my annual stuff....one thing that I have never gotten to the bottom of since I owned this boat...is the terrible vibration it has when at idle speeds in the water....on the hose it idles fine, could be that I don't put it in gear on the hose though....but in the water at wakeless speed, the whole boat shakes...once you open it up a little, it seems to go away...I'm thinking something in the drive...maybe even an out of balanced prop? Anything else I should be looking at?

21' Lavey XtSki, 454mag, B1 with -2 imco lower...not sure of the prop size or type, its not marked, at least not on the outside

 

[mash on it]

Have you tried a different prop?

Dan'l

 

[RiverDave]

It’s the exhaust.. and it’s normal

 

[Mototrig]

It’s the exhaust.. and it’s normal

My first boat with through transom exhaust did this.
Scared the crap outta me when I backed it off the trailer for the first time. Whole boat shook. Thought the prop was loose.

 

[Badchoices03]

My first boat with through transom exhaust did this.
Scared the crap outta me when I backed it off the trailer for the first time. Whole boat shook. Thought the prop was loose.

Could it be because the through transom exhaust is below the water level? I just realized that of all of the boats i have owned with through transom exhaust were above the water...it really shakes the boat, so I was thinking something is wrong

 

[Teague_JR]

it could be that the engine is idling too slow when the exhaust is submerged in the water... or the air idle control (IAC) valve is no longer working if its an MPI...

or there could be nothing wrong and its just the exhaust reverberating with the water level and swim step

 

[Badchoices03]

it could be that the engine is idling too slow when the exhaust is submerged in the water... or the air idle control (IAC) valve is no longer working if its an MPI...

This is what it feels like...almost like its struggling to stay at idle...infact I don't even take the boat off the trailer until its at like 160degrees, otherwise it will die...its not an MPI...

*edit to add - The guy I got the boat from said it always ran like that, and always had to be really warmed up to run...the motor and drive have ECM stickers on them and the previous owner showed me a receipt that they had just done a tune up and service the month prior to me buying it...so I just took it at his word that it was just the way the boat ran...

 

[Racey]

What is the idle RPM?

The vibration is probably the exhaust combo off the swimstep.

If you have a big RPM drop when you go into gear the motor could be right at the cusp of stall speed... Bump the idle up a bit,

What carb is on the motor? Might want adjust the idle fuel mixture

 

[Teague_JR]

Turn this little guy clockwise a quarter turn or 2 or 3

You have to final tune a carb in the water not on the trailer. It trying to die when cold means it’s probably a bit lean AND idling too slow when exhaust is submerged. But if it never dies when it’s hot then leave the idle mixture screws alone for now

Warm neutral idle in the water should be 750 rpm or so

 

[Badchoices03]

What is the idle RPM?

The vibration is probably the exhaust combo off the swimstep.

If you have a big RPM drop when you go into gear the motor could be right at the cusp of stall speed... Bump the idle up a bit,

What carb is on the motor? Might want adjust the idle fuel mixture

I would have to look the next time I take it out to see where idle is at.

The carb is a Holley Demon, not sure of CFM

 

[Badchoices03]

Turn this little guy clockwise a quarter turn or 2 or 3

You have to final tune a carb in the water not on the trailer. It trying to die when cold means it’s probably a bit lean AND idling too slow when exhaust is submerged. But if it never dies when it’s hot then leave the idle mixture screws alone for now

Warm neutral idle in the water should be 750 rpm or so

View attachment 1216331

Great info...it definitely never stalls once its warmed up, but I have to sometimes hog the boat ramp because I cant pull it off the trailer until it warmed up otherwise it will die, so it takes me a few minutes running on the trailer to get her up to temp...

I will take note of the rpm next time out, which might be this weekend if I can get my other maintenance done...

 

[Mototrig]

Could it be because the through transom exhaust is below the water level? I just realized that of all of the boats i have owned with through transom exhaust were above the water...it really shakes the boat, so I was thinking something is wrong

On my boat the water level is a shade below the exhaust. If I reverse anything above 1200 rom the water plows up the transom covering my shinny Eddie Marine stainless flaps I spent all day polishing ..... Shakes the boat. Now I just reverse at idle speed

 

[LHC Kirby]

Great info...it definitely never stalls once its warmed up, but I have to sometimes hog the boat ramp because I cant pull it off the trailer until it warmed up otherwise it will die, so it takes me a few minutes running on the trailer to get her up to temp...

Depending on transport time from house to ramp and of course normal ramp traffic.

Can you warm up at home, and therefore not be a launch ramp hog ? I realize it’s a PIA to do everyday - but if you can avoid being a hog

 

[Badchoices03]

Depending on transport time from house to ramp and of course normal ramp traffic.

Can you warm up at home, and therefore not be a launch ramp hog ? I realize it’s a PIA to do everyday - but if you can avoid being a hog

I do that on occasion, but not often for two reasons, I don’t really like running the boat on the hose, and it’s really fkn loud and I try my best to be a courteous neighbor

 

[BIGRED9158]

Wait I thought you were selling this thing

 

[Lumpy]

Agree with RD but waiting until 160 water temp? 454 MAG...how many hours?

 

[LHC Kirby]

I do that on occasion, but not often for two reasons, I don’t really like running the boat on the hose, and it’s really fkn loud and I try my best to be a courteous neighbor

Ah …. You are that guy - idling on the ramp with a loud boat and I can’t talk to anyone on my boat until after I get out of the marina. Got it

 

[Badchoices03]

Ah …. You are that guy - idling on the ramp with a loud boat and I can’t talk to anyone on my boat until after I get out of the marina. Got it

Actually no, because once it’s in the water, the exhaust is below the water line, so it’s quiet…it’s only loud when not in the water.

 

[Badchoices03]

Wait I thought you were selling this thing

At one point I was thinking about it…

 

[Badchoices03]

Agree with RD but waiting until 160 water temp? 454 MAG...how many hours?

I am not entirely sure, there is no hour meter

 

[RiverDave]

Actually no, because once it’s in the water, the exhaust is below the water line, so it’s quiet…it’s only loud when not in the water.

If it’s shaking the boat I’d bet it’s just the exhaust. It definitely needs a little carb adjustment though if it’s dying on you.

 

[dspracing]

My XTski did the same thing. Even worse when there were wakes. My only complaint about that boat.

 

[Badchoices03]

My XTski did the same thing. Even worse when there were wakes. My only complaint about that boat.

Interesting...good to know..

 

[Nanu/Nanu]

Im betting on a carb adjustment/tune.and just and exhaust underwater deal. My exhaust is above the water line and when i go in reverse it feels lime something is insanely wrong when my flaps shut in reverse haha. I gots me a 454 too!