Ventilation from bent prop shaft or power head ?

[Mylittlemoneypit]

Hi first post here. I'm a real newbie. I have purchased a 20ft triton with a 2006 Merc Pro XS 225. All of a sudden the boat will not come up (or will barely) come up on plane. The nose goes way up and it throws water ten foot high. But unless I just go WOT and hold it there it won't get the nose out of the air. When I do go WOT it takes about 3-4 minutes to come up on plane all the time throwing water straight up and vibrating the boat tremendously (trim is all the way in/down). The local boat retailer said it was a bent prop shaft. I decided in a genius :facepalm: moment to figure it out myself. I have completely torn down the lower unit. There was water in the oil, the prop shaft was 5 thousandths off (tolerance is 7 thousandths) but no gear damage and no bearing issues. Now I'm putting this together (with new prop shaft and drive shaft, new seals, and some new bearings) and I'm questioning whether I have chased the wrong cat up the wrong tree. Could this be a power head issue? How do I check for that? Anyone had this experience before? Any help would be appreciated.

 

[Dukedog]

Re: Ventilation from bent prop shaft or power head ?

Wrong cat.... A prop shaft bent bad enough ta do that would take out seals and internals pretty quick. Not a ph problem either unless your down on rpms at launch. Have you noticed any difference in that area? Prop/hub and/or trim type problem. Shouldn't get any kinda continuous "rooster tail" and/or "bow in tha air" when its sucked up tight against tha boat

 

[Mylittlemoneypit]

Re: Ventilation from bent prop shaft or power head ?

Thanks for the reply Dukedog. No issue with RPM's at launch. Trimmed it all out/up and back in/down several times to be sure of where the prop was at launch. I can't really say it was a rooster tail. Really more of a splashing and vibrating. Not sure, stumped. Any other ideas? Thoughts?

 

[Dukedog]

Re: Ventilation from bent prop shaft or power head ?

Donno? Kinda leaves me in tha truck without really being there...............

 

[MH Hawker]

Re: Ventilation from bent prop shaft or power head ?

bad hub on he prop.

 

[Dukedog]

Re: Ventilation from bent prop shaft or power head ?

Wouldn't think it would hold tha nose up and eventually breakin' over without tha rpm increase from tha norm..........worth checkin' anyway.

Shoulda ask earlier. What is your WOT rpm on it now? Reason I ask is just because ya got tha throttle pushed all tha way down ta WOT may not mean tha motor is comin' up ta real WOT rpm....What is it after it does finally break over..........

 

[carholme]

Re: Ventilation from bent prop shaft or power head ?

Did you operate the boat previously without a problem or was this the first run for you as the new owner? One thing to eliminate if this is your first run with the boat, is how high your engine is mounted on the transom. Does it closely match the installation as see in this link and is the cavitation plate close to the lowest point of the boat bottom?

Outboard Motor Shaft Length

Gerry

 

[Mylittlemoneypit]

Re: Ventilation from bent prop shaft or power head ?

Thanks guys,
The core was my first thought too. But, it's steel on steel no rubber in this one.
I will call Triton today and get specs on motor height, etc. Thanks Gerry.
Dukedog, that is a great question. Yes WOT is lower until it comes up on plane. Than it opens up. WOT at this point is 5800 RPM's.
this is the first time with this problem. But we have used the boat about a dozen times. We did lower the motor (to slow it down and help with chine walk, my oldest is 16 and only knows WOT) 1/2 inch. Since that time we have been out 3, or 4 times. Hope I answered all the questions guys.

 

[Dukedog]

Re: Ventilation from bent prop shaft or power head ?

Really hard ta decipher without "being there".

What gear case ya got? How many water inlet holes on tha side? Kinda prop?

General rule a thumb on tha bass boat motor height starting height is "center" of prop shaft 3 1/2 inches below tha bottom of tha pad. That's with tha bottom of tha boat level and tha cavitation plate on tha motor level. Measure tha distance to each from level ground. Difference is motor height. You can go up or down in 1/4 inch increments from there. A water pressure gauge is a "must have". You really have to monitor tha gauge when doin' this. Moving this around it will optimize performance and handling. But tha key here is "seat time", learning how ta drive tha boat on tha pad at speed without all tha chine......OR whatever your comfortable with! Just pay close attention ta tha pressure gauge. If it drops when your at speed or making a turn, drop tha tha motor a tad and try again till ya get to tha "sweet" spot where everything is holdin' steady................

 

[MARV1]

Re: Ventilation from bent prop shaft or power head ?

Water in the boat?