prop guru's I have a riddle...

[Thad]

Not really a riddle, more of something I can't figure out.

21' Conquest/5.0 Volvo Penta SX

I have four props, one is only a spare and has never been on my drive.
The other three are all Volvo OEM aluminum props.
A 19p, a 21p, and a 25p. All cupped and checked for balance.
Here is the thing. My 25 used to give me great plane and 54mph. My 19 used to give great power out of the water pulling tubes, and if you weren't paying attention, it would throw you out of the back seat.
I have been noticing with my 25 that I have lost my top end (48) and my hole shot has increased slightly. My 19 struggled Saturday to get the boat out of the water pulling me big tube. My 21 now seems to have the best hole shot and top end (49) of all three.
I did not send my props in to be looked at this winter as I did not see any nicks or damage to any of them. Nothing in the motor or drive has changed, to my knowledge. Hubs all appear to be tight.
The spare is a Michigan Wheel 19p three piece unit. I assume it would perform different from the others because of make, so I am going to try it this weekend as a comparison test to the Volvo 19 prop.
Speeds are from Garmin GPS hand held unit.
Any ideas on what is going on with my props, drive, motor?

 

[Thad]

Re: prop guru's I have a riddle...

Sorry, forgot what could be one piece of vital information.

The 25p used to be a 23p. It was resized two years ago.
The 19 and 21 are origional.

 

[sschefer]

Re: prop guru's I have a riddle...

Given that the props have not changed noticibly, my first inclination would be to check for a dirty fuel filter. Sounds to me like you're leaning out and not producing the power you need to get the performance you once had.

 

[Bondo]

Re: prop guru's I have a riddle...

Nothing in the motor or drive has changed,

Ayuh,... Sounds like you missed your Annual Tune Up,+ Service....

 

[steelespike]

Re: prop guru's I have a riddle...

I agree something is up with your motor.Perhaps your only on 7 cylinders
you wouldn't be the fiirst to not notice,especially on a V8.
Could be as simple as a plug wire off.Throttle may not be opening all the way. Could be a compression problem.Is the bottom clean?

 

[Thad]

Re: prop guru's I have a riddle...

I clean the hull regularly and wax it once a month.
There is no water in the bilge.
Fuel filter/water separator was replaced middle of last season.
I have the valves and rockers adjusted every spring.
I did get fuel at a station that I have never used before. And I hold 50 gal. so it might take a while to run that out to test that one.
Something I did notice two weeks ago with my 25 when running against my buddies new prop, I had to trim exraordinarily high to get my rpm's up to 4500. Normally, I get to 4700/4800 and have room left to play with the throttle a little. Seven cylinders is sounding more probable the more I type.
I did not run full trottle last weekend because the water was pretty chopy.
But that IS when I noticed the boat did not want to get out of the water.
Something I did this spring also is change the gimbal bearing. That would not slow me down, would it?

 

[QC]

Re: prop guru's I have a riddle...

Something I did this spring also is change the gimbal bearing. That would not slow me down, would it?

If your gimbal bearing is slowing you down, it would be screaming bloody murder and you have some serious issues coming up. Short answer? No.

 

[sschefer]

Re: prop guru's I have a riddle...

I don't want to dwell on the fuel filter possibility but letting one sit all winter can be all it takes to gum up a filter. Today's fuel/water separators come in basically two setups. A 10 micron filter for fuel injected motors and a 21 micron filter for carbed engines. Change it, it's cheap and make sure you get the right one or performance will suffer.

 

[Bondo]

Re: prop guru's I have a riddle...

Fuel filter/water separator was replaced middle of last season.

Ayuh,.... Even Yesterday is Old if you got a dose of Water last night....

And,......
I see Tune Up mentioned,.. No where....

 

[Thad]

Re: prop guru's I have a riddle...

I did not have time yesterday to look at the boat, so I am leaving early today to find the culpret of my woes.

I was going to change the plugs and wires this spring.
The mechanic at the shop where I bought the boat said I did not need to. I changed them two years ago.
I did have the valves adjusted this spring.
This problem started two weeks ago.
A buddy of mine said something about an exhaust flap maybe being stuck? Where is this flap and could that be a possibility?


Here is a break down of events starting the Friday before;
Replaced starter.
Put in storage totes under sun deck. (I always wait until I have been out a few times to make sure I do not have to climb in there)
Saturday, bought gas at Shell in a small town on way to Mississippi River.
Now that I think of it, I never run Shell gas, my last boat ran like **** on their fuel.
But, the engine seems to run smooth, did start a little harder than normal last time out.
No additional weight was in the boat either time I noticed a problem.

I am going to replace fuel filters. Add some gas/fuel treatment. Check all plug wires, cap, rotor, and plugs if needed. Check the fluid level in the outdrive. Check that all belts are tight.
Anything else I should check before putting on water? I will put on the 25p prop to see if WOT and top end can be reached.

Anything else I should check or do, should I leave the 19p on to see if I can get out of water? I am getting pretty worried about this ordeal. I was really hoping it was the props.

 

[MikDee]

Re: prop guru's I have a riddle...

We really need WOT (wide open throttle) rpms to help. 54 mph is quite fast for your combo, unless your boat is a speedboat style, & very light.

 

[Thad]

Re: prop guru's I have a riddle...

She is a fast boat. I think it may have more hp than the 220hp i said..
I bought her new and was told it was 260 hp. But everything I read says the without EFI, that engine only makes 220. She is carbed with a manual fuel pump.

With the 25p prop, she will run WOT at 5000rpm. I do not run her that high, I keep her around 4600-4800. I trim down to get the rpm where I feel comfortable. The top speed of 54 is on smooth water with a light load.
She will cruise at 49 @ 4700.
The 19p will jump the boat on plane under a heavy load. WOT with that prop will exceed my limits. So I only use it for pulling inflatables.

The problem is, two weeks ago, to get the rpm's to 4500 I had to trim up higher than I should have and probably higher than what is safe. The trim needle was right at the line. And I was only getting 44mph.
With the 19p pulling the tube, she struggled to get out of the water.
The nose stood up and she plowed. (And yes, I was trimmed down all of the way.) Even without the tube behind, it felt like the bilge was full of water. She just didn't have any guts.

 

[MikDee]

Re: prop guru's I have a riddle...

I see, it must be a fairly new boat with a Vortec 5.0 then, to develop that much power. There are 2 things I would start with, 1) I would check the timing advance to see if it's working properly, giving you full advance (it's probably electronically controlled) 2) Check out your fuel tank vent, ( you can temp. take off the gas cap under power to try this) then your fuel delivery system, the fuel filters (including the one in the carb), and the filter in the tank, plus the mandatory antisiphon valve there (make sure it's not getting clogged), it's a one-way flow valve, out of the tank >, if it's working properly.

 

[steelespike]

Re: prop guru's I have a riddle...

Did you check for a plug wire off? you might want to look at the plugs see if one seems wet or fouled ,different looking.There is an outsaide chance of a bad head gasket.That could cause a plug to appear extra clean or have a little rust on it.
Don't modern I/O engines have hydraulic lifters?

 

[Thad]

Re: prop guru's I have a riddle...

I did not know there were filters on the carb and the tank. I have only changed the fuel/water filter.

When I say the lifters adjusted, I guess what I mean is, the rockers were rattling, so my mech. adjusted them. I thought it was the same thing.
There are nuts on the rocker studs and some were, as he said, out of adjustment.

With a head gasket, would'nt I notice a rise in operating temp, water in oil, or water in bilge?

 

[MikDee]

Re: prop guru's I have a riddle...

I did not know there were filters on the carb and the tank. I have only changed the fuel/water filter.

When I say the lifters adjusted, I guess what I mean is, the rockers were rattling, so my mech. adjusted them. I thought it was the same thing.
There are nuts on the rocker studs and some were, as he said, out of adjustment.

With a head gasket, would'nt I notice a rise in operating temp, water in oil, or water in bilge?

If it's Quadrajet, there's a big nut on the carb where the fuel line goes in, there is a small plastic (waterproof) filter there that needs to be cleaned or changed on occasion, and every fuel tank usually has a filter, & an antisphon valve from the factory.

A lifter adjustment is needed if they're tapping, but as long as the mechanic knew what he was doing, and didn't make them too tight! Or that could be your problem? Did this issue begin after the valve adjustment, or you're not sure?

 

[Thad]

Re: prop guru's I have a riddle...

A lifter adjustment is needed if they're tapping, but as long as the mechanic knew what he was doing, and didn't make them too tight! Or that could be your problem? Did this issue begin after the valve adjustment, or you're not sure?

My mech. who is a good friend of mine, builds race engines. He has also been after me to let him add some hp to the boat. If it IS a head gasket, he might just get his way.
I would bet my boat that they are not too tight.

He did them in late April. It was just two weeks ago that I started having problems.

 

[MikDee]

Re: prop guru's I have a riddle...

Okay, sounds good! I don't think it is a head gasket, or you would be misfiring, or getting water in a cylinder, or two,,, besides, it appears to still be running pretty strong. Check out your fuel system.

 

[Thad]

Re: prop guru's I have a riddle...

Thanks all of you.

I love this place. I found it by accident a month ago and I wish I would have found it much sooner. The wealth of knowledge here is amazing. And every now and then, even I get to help somebody.

I will feed back on this thread later in the week to let you know what I found or did not find.
I am finishing up some last minute things here at work before the holiday so I can get outta here and work on my boat.