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Prop question.

Fishnut

Fishnut
in This Old Boat

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Fishnut

Fishnut

Posted
Posted

I think I need a different prop. My boat is a bay-liner 2452 with a 5.0L engine.

It’s a pretty heavy boat. When I try to get up in plane it takes for ever, I push the throttle to 5500 rpms and it takes about 5 minutes to get up on plane. Then I can back the throttle down to 4200 and it will be about 24 mph. I have a 16 pitch prop.

 

I have to get up over 18 mph to get on plane. Yes I have my trim tabs down but it doesn’t seam to make any difference.

Please help I’m not sure what pitch prop to try next??????

 

 

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Kaz

Kaz

Posted
Posted

Hey buddy I did have a same problem on my boat. Try 14 pich and 4 blade prop. Buy cheapest one and see if make any difference and don't put your trim tabs all the way to the bottom try half way first

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sherman brown

sherman brown

Posted
Posted
  • I was having the same problem with my 21' boat with a 19p 3 blade when loaded up for fishing erie. I went to a 19 pitch high five and now she jumps on plane. only takes a few seconds to get up. she stays on plane at slower speeds and I have much better handling with the 5 blade. you need at least a 4 blade but a 5 would be even better.
mr 580

mr 580

Posted
Posted

Mercury has a online prop selector where you input your boat info- hull type, engine/drive, weight and application.  Seems like a good place to start.  I don’t know specs on your 5.0 engine, but tend to think that at 5,500 rpm you are pretty much maxed out. A higher numerical pitch should pull rpm down.  I had a 5.7 mercury that would run about 5000 at wot.  Reducing weight or moving it forward would also help.

Bozeman Bob

Bozeman Bob

Posted
Posted (edited)

I believe the maximum RPM for that engine is 4400- 4800. If your hitting 5500 with a 16p there is something wrong . Before buying a prop I would verify the tach with a hand held one at the very least. The boat itself is underpowered so with a load it will be a slug coming out of the hole.But no way is it hitting 5500 and not popping up on plane. I wonder if you have spun your prop hub , that would allow the RPMs to hit 5500 or until you blow the engine and your planning speed would also be affected as the prop is always slipping. 4200 rpms should be close to WOT if propped correctly. I would borrow a prop before buying anything . Most boat's are set up to run 17-19" props. So it wouldn't surprise me if the PO didn't put that 16 on to compensate for it being light on the HP.

Edited by Bozeman Bob
rolmops

rolmops

Posted
Posted
2 hours ago, Bozeman Bob said:

I believe the maximum RPM for that engine is 4400- 4800. If your hitting 5500 with a 16p there is something wrong . Before buying a prop I would verify the tach with a hand held one at the very least. The boat itself is underpowered so with a load it will be a slug coming out of the hole.But no way is it hitting 5500 and not popping up on plane. I wonder if you have spun your prop hub , that would allow the RPMs to hit 5500 or until you blow the engine and your planning speed would also be affected as the prop is always slipping. 4200 rpms should be close to WOT if propped correctly. I would borrow a prop before buying anything . Most boat's are set up to run 17-19" props. So it wouldn't surprise me if the PO didn't put that 16 on to compensate for it being light on the HP.

x2

Every 1 inch pitch down will raise your rpm by about 200. You will not want to go WOT at 6000 rpm. You probably have a spun hub.

Fishnut

Fishnut

Posted
  • Author
Posted

I have 2- 16 props, 1 was brand new they both acted the same. They act like there not grabbing enough water. As for weight I have added a 9.9 4 stroke, but it acted like this before I put the kicker on.
This winter I’m moving all my batteries up front hoping this helps.


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Sk8man

Sk8man

Posted
Posted (edited)

I know this could be irrelevant but if this is a change in the way the boat comes up to plane since you've had the boat you may wish to check for water logging of the hull/transom and weight distribution within the boat.

Edited by Sk8man
Bozeman Bob

Bozeman Bob

Posted
Posted

How long have you owned this boat and when did it start having these performance issues ? A boat that is hitting 5500 immediately coming out of the hole should be on plane right away,unless it has huge amounts of prop slippage. How many rpms are you seeing at WOT when on a full plane ? If you go to a higher pitch,in theory it will take you longer to get on a plane , that's the head scratcher as the 16 should jump, unless the diameter is 12 - ×13" . At any rate you are over revving it to death. Try borrowing some props before buying and verify tach accuracy. 

Fishnut

Fishnut

Posted
  • Author
Posted

The boat has always been stored in doors. And it’s a solid core. (No water log) the boat has always had a problem getting up on plane. At wot it will hit 5800 rpms, I have checked it with a hand held tack and it’s accurate. My prop hub is not slipping. It seams like the prop is too small, not pushing enough water. If I cut the throttle down to 3000 rpms the boat will come off plane.


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Bozeman Bob

Bozeman Bob

Posted
Posted (edited)

3,000 rpms is normal cruising rpms for a gas powered inboard and is usually around 20-22knots. Judging from what your saying I would guess that you have a small diameter prop and that's where your prop slip is coming from. I would try borrowing a 17" Mercruiser prop and take it from there. I also would have my hand on the throttle to keep it from going past 4800 rpms.Looking at the picture of your boat and trying to push it with 230 hp your asking a lot out of that engine. So 17 may give it a better holeshot and get it closer to your redline.I have a few props kicking around if you cant find anyone local to borrow one from. After you get a base with a semi close prop you can go 4 - 5 blade or whatever , but I wouldn't just drop a few hundy on a new prop with out verifying what the actual problem is.

 

 

 

 

 

 

 

Edited by Bozeman Bob
  • Like 1
bout time

bout time

Posted
Posted

Honestly a boat that size with that motor is underpowered. I have a 25’ trophy hardtop with a 5.7 and had similar issues. I ended up dropping the prop 1” in pitch and going to a 4 blade. It helped but still dogs at times. Another issue is the placement of the fuel tank. Instead of being true “midship” they are more towards the rear 2/3 of the vessel. It just adds extra weight to the stern along with regular motor, trolling motor, riggers etc. If I carry anymore than 60 gallons of gas at a time I have a hard time getting on plane.


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  • Like 1
sherman brown

sherman brown

Posted
Posted

im my opinion you need to go to signaturepropellers.com and contact then about a 14 1/4 x 17p 5 blade propeller or a 14 1/4x15p. I have a 21' glass boat with a 5.7 mercruiser. I know my boats a little smaller but with this prop its just amazing how quick it gets on plane and stays there. I switched to the high five 13 1/4x19p from a 3 blade 19p and was amazed how much difference it made. went looking for a spare and came across the 14 1/4x17p and tried it and have never looked back. I do think I had to cut a small section off the anode on the outdrive so the 14 1/4 would clear the anode. they do make this prop in a 15p. but I turn 5000 rpm's at wot with my boat. I think 4800 is what rpm's these motors are rated at. if you go to larger diameter than 14 1/4 your motor might have trouble turning it. but with your boat i'd think about the 15p. these 5 blade props will keep you on plane at much slower speeds.

 

talk to them at the wed site and explain the size boat the prop you have now and your problems and see which prop they recommend.

 

a 305 has less hp than the 350 but the 305 is supposed to have more low end torque. this should give you a better hole shot than a 350.

  • Like 1

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