Beat up old prop causing over-revving?

[chillin014]

Re: Beat up old prop causing over-revving?

alright well..this is probably my conclusion since there seems to be no resolution to my problem short of a new motor or boat.
I took the boat out today with the cupped prop. The rpms at wide open throttle were noticeably lower, it was staying under 5000. That is not necessarily in the efficiency range of the motor, but whatever. The speed was topping out at MAYBE 25 MPH if I was on some really smooth water going dead straight.
I think that's just all she's got. It's kind of sad that its not very fun to pull anyone on an intertube or anything of that sort...but the boat was a hand-me-down so I can't really complain. Maybe if the compression checks out low I will find the time and motivation to rebuild the motor, assuming I dont just try to get another boat.
thanks everyone for the help.

 

[chillin014]

Re: Beat up old prop causing over-revving?

in case anybody cares, I did a compression check on the motor today. According to my service manual both cylinders are supposed to be at around 150psi and the top one came in at around 130 and the top one 140. This sounds like good news to me seeing as how if there is a power loss problem it may be an easier "fix" than I thought. I'm wondering if a new carb and fuel filter might revive it a bit?

 

[coolguy147]

Re: Beat up old prop causing over-revving?

i dont believe you would find power lose. after you fix all the prop stuff would suggest a decarb so it will even out more

 

[Paul Ryan]

Re: Beat up old prop causing over-revving?

Did you find out about the weight? The flotation foam in my old bayliner was drowning from water. Boat loast around 350 pounds after I got the foam and water out of it.

 

[chillin014]

Re: Beat up old prop causing over-revving?

Sorry for the LATE reply, I didnt get any notification emails.

coolguy- I've already got the prop stuff sorted out, what do you mean "de-carb?"

Paul- No I never did weigh it, I really ought to do that. I may run it over a scale within the next month for the hell of it. If it turns out that it is extremely over-weight I may start to consider selling the damn thing.

 

[Paul Ryan]

Re: Beat up old prop causing over-revving?

It really sounds like your engine is doing it's part. And with your prop being reworked you now have something to work with. In doing Base Line prop test "weight" is a huge part of the test. 300 extra pounds in your rig would make a big differance when looking at RPM's and speed... If your guessing at one of the spec's then all you can do is make a guess at what the next step should be. And sometimes we guess wrong Well atleast others might, I don't Got to get hard numbers.

Sounds like you are over proped now with the rpms being under 5000. So taking a little cup off the prop would get your rpms back up and engine working in is range. But still not knowing weight we really can't say anything definitive about overall preformance. Were all are just guesing. I would not spend anymore money or time on anything until you can answer weight! My two cents

On a side note. I am going through the same thing with my rig!!! It's my first boat so I am walking through all the differant steps so I can make good sound decisions when I go off and spend money and time. I have rebuilt my engine, put it in the water and know that at WOT the engine is at 4400 Rpms and running 32 mph (gps). Spec WOT RPM's is 4800. Those are hard numbers! I am over proped. BUT, like you I dont know my weight.

I'm going to fill up both the truck and boat tanks full of fuel. I'm going to scale the truck/boat together, Then I will scale just the boat/tralier. I will walk away with over all rig weight, truck weight, and boat/tralier wegth. I will then unload the boat, fill the truck up with fuel, go back and scale tralier/truck. I will walk away with trailer weight.

When I go to buy a prop, or fix what I have or whatever I know that I will be making a good choice because I have all the info I need to MAKE that good choice when I go to spend money. I don't have the money to be buying three or four props. I'm going to hopefully by ONE prop, put the boat at mfg spec's and enjoy

Wow this turned out long..Sry Let us know what you find out.

 

[chillin014]

Re: Beat up old prop causing over-revving?

I hear you. Trust me...I'm about done spending money on it without knowing for sure I'm making a difference. But the motor wouldn't even start last time I took the boat out so I have problems other than water-saturated foam.

Regardless, I'm just as big on facts and numbers as you are, and would love to know the weight of the boat just to curb my curiosity. I was hoping I could actually park just the trailer on the scale somehow though so I could just subtract the trailer weight from the total.

 

[Paul Ryan]

Re: Beat up old prop causing over-revving?

The three steps I'm going to do will give all the info you need.

1: Truck/Boat/Trailer/Fuel Tanks Full.
2: Boat/Trailer/Fuel Tank Full
3: Truck/Trailer/Fuel Tank Full.

With number 2, I will disconnect the truck and drive off the scale.
With number 3, I'm going to drop the boat in the water and let my friend stay with it. I trust him and he knows what he's doing around boats.

Subtract YOUR weight from 1 (if u stayed in truck during #1)
Subtract 1 from 3 and your weight (if you stayed in truck during #3) you get Boat weight.
Subtract 2 from Boat weight and you get trailer weight.

You'll know all

 

[chillin014]

Re: Beat up old prop causing over-revving?

Oh do they have weigh stations at your lake or something? I dont live near water so removing the boat and coming back to town to weigh is a major inconveinence haha.
I might have to do one weight with the boat&trailer attached to the car, and one without.

 

[Paul Ryan]

Re: Beat up old prop causing over-revving?

O...Forgot your not here OK...I have done this before. Then you could weight car/trailer