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Update on prior postboat not getting up to speed

L

lugnutdan

Contributing Member
"Prior post,my 1996 trojan 350

"Prior post,my 1996 trojan 350 express/ twin 502 xl,was onlyu getting 14kt at 3200 rpm.
Finally took her out check vitals more closely.
took her to 4200 rpm W.O.T,she got up to 22kt.
engiens got right up there,trim tabs working.
no vibration,no hesitations,just cant get the speed out of her.and I dont have any indication
trannys are slipping.had an extra gps to check my speed both are reading the same???W.T.F.
would this point you expirenced gus to the props,just had a bottom job,everything clean
diver went down and said the only thing he sees is each prop looks like its been sand blasted,about an inch up each prop.
and i remember going thru some mud a couple of months ago,but that really didnt feel like much.
my machanic whats to test fuel pressure.
but if getting rigt up to 4200,can it still
be that???

ANY HELP WOULD BE GRATEFULL,WERE DO I LOOK NOW."
 
"So used to do 35 kt at 4200 R

"So used to do 35 kt at 4200 RPM and now is still get to 4200 RPM but isn't making speed?

With no vibration or shuddering, I doubt you hosed the props going thru the mud. I don't see any benefit to a fuel pressure test as the engine is making a reasonable RPM under load.

Something in the drive train is slipping. If the speed is steady, at 22kt, I'd suspect the transmissions slipping. An optical tach will tell you for sure. If the keys shear, they usually don't slip, they spin. You can always check the line pressure in the gears.

A simple thing you may check is to make sure the control valve on the gear goes fully into forward when the control goes into forward. If the control lever doesn't go all the way into gear, the oil flow in the gear is reduced and slipping is possible. The last simple thing is to check the fluid level in the gear to make sure it is full."
 
"If it's slipping, it won&

"If it's slipping, it won't be doing anything very soon! A tranny can't dissipate that amount of horsepower without frying itself in short order.

I suspect your props are out of whack: either bent out of pitch, or barnacled up. Also a possibility is massive crud hanging on the hull.

The hp is gotta be going somewhere since the motors are making good power.

Jeff"
 
This is too weird. Did the bo

This is too weird. Did the boat run OK just after the bottom job? Is the boat bilge empty?
 
"I had read a post about a man

"I had read a post about a man who had made an appointment with the marina to haul his boat for a few hours. Of course when he called the marina about being late since he could not even get up on plane, they ultimately found the bottom loaded with massive crud."
 
"Sorry guys,I got busy,I had a

"Sorry guys,I got busy,I had a bottom job done in
july,and had a diver down twice,in a month .
Theres nothing nada,on the bottom wraped around the props,the only thing he saw one shaft zinc missing,and each prop looked like it was sand blasted all the way around the prop about an inch high.
About 2 months earlier I went thru a shallow spot felt the boat shuder once or twice,i dont really run fast in the boat really just pudder around,a month later I finally opened her up and thats when I noticed she wasnt getting up to speed.
Everyone is talking props,but im stumped."
 
"Danny, That 1" prop polis

"Danny, That 1" prop polishing is likely nothing. My props were the same way when hauled 3 weeks ago. I have no difficulty or vibrations and plenty of shallows to barley float in spots. Are you sure about previous speed measurements?

My 2550 Bayliner HARDLY makes 15 kts with 4 people and a full tank. That's why it is already out of the water and the TRIPLE the weight Silverton does over 30 kts...That one stays in til after Thanksgiving"
 
"I got this boat in febuary,an

"I got this boat in febuary,and thought i had her up to 34 kt,like I said i very rarely opened her up.done a lot of work on her,but I believe this boat should do between 32 and 36 kt.
we are living aboard,but dont really have a lot
of crap aboard,I just hate to spend $800.00
on taking them off and looked at.
I believe if you bring your props,in,its like asking a machnic if you need an aligiment,the answer is you always need one."
 
"I'd suggest using a PropS

"I'd suggest using a PropScan shop. They will show you the data from the scanning process which will allow you to mmake an independent assessment of the props' condition. If they correct them, you'll get an 'after' scan, too. All I know that have gone this route have been very satisfied."
 
"thanks mark,joe im not sure w

"thanks mark,joe im not sure what coupling keys are,(.jeez now i fell stupid)are you talking about the key where the shaft and prop meet under the boat???"
 
"I think that they are talking

"I think that they are talking about the other end of the shafts, where the shafts meet up to the trans flange.

Fred 156-M"
 
"YES If the propeller shaft ke

"YES If the propeller shaft key shears, the shaft taper and tightness of the shaft nuts will allow the prop to operate normally at low loads and then slip on the shaft at higher loads.
Rare but I have seen it before.
Joe"
 
"I was towed in 4 weeks ago un

"I was towed in 4 weeks ago under that same condition. However, Dan... I still question how you know you were originally cruising at THAT 32 kt. speed and not something other than THAT speed? Was that a GPS measurement as well?"
 
"now im trying to remember i b

"now im trying to remember i believe,when i first got the new gps chart plotter,i brought her up to 34 kt,now you got me questioning my own sanity.Is there any where i can go to get this info. on the computor."
 
Your chartplotter may be able

Your chartplotter may be able to "replay" track logs or have them transferred to a computer for further detail. The Garmin I use as well as Raymarine have PC/MAC based nav software that will enable those functions if available.
 
"I used to cruise at 18 20 kt

"I used to cruise at 18 20 kt at 2800,that was gps,and i remember i had 34 36 kt at W.O.T.
So yes it is suppose to do this,im sure."
 
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