need some prop info!

[icyb]

new guy here great site. bought a boat from a widow and not knowing much about it, i did some crawling around it and did some maintenance. good compression new impeller new shutters cap rotor plugs wires coil. the boat has always been garage stored. engine is a570967 drive is oa576888. merc 260 with 1.5: 1 ratio. boat weighs 3800 dry and is 21 footer. i fish lake erie with 3 people and half tank of gas is 50 gallons. small lake near me is calm and wot is 4000rpm and 40 mph on lowrance gps. the boat came with only one prop a hi5 mercury 13/1/4 by 19 pitch. found out factory prop was a 13/3/4 21. engine runs good carb checks out, i dont know why i cant spin the 5 blade faster. its good on rough lake erie. im not after anything , just get the rpms to 4600.

 

[Maclin]

Welcome Aboard!

Are you trimming out the drive once it gets on plane? If so, you may have an engine performance issue, or a lot of extra waterlogged weight. A Merc 260 with 1.5 ratio in a 21 footer should hit max rpm's with a 19p of any ilk.

Looks like it has electronic ignition, so no points involved. If distributor has not been moved then timing should not have changed, but have you checked the timing?

What made you change the shutters? Were they missing or otherwise not complete? Old ones could have dropped down the tube and ended up blocking the exhaust inside the boat or in the outdrive. Did you check there when you removed the drive and split it for the impeller?

 

[Maclin]

Just looked at the load you described, that is a lot of fuel. Still, with that plus 4 bodies and the 19p should be able to hit lower end of the 4400-4600 range. The Hi5 is pretty good at holding in the chop, but seems you are lugging the engine and need to find out why.

What were the compression numbers?

If the tach is accurate, showing about 16% slip. That is bad for a Hi5. Describe the trimming method you use, be sure you are not plowing. Then back to the actual weight, that is a lot of slip. The hull could be hooked, but let's get some more answers before we go there.

 

[icyb]

the inland lake near me is mostly very calm, three adults one child half tank 4000 wot 40 gps speed. by myself one quarter tank 4100 rpm and 41 mph . the shutters where clicking at trolling speed. everything was clear at the bottom of the y pipe, boat runs at or under 160 temp. lowest compression was 135 and highest about 150. i just wonder if a three blade 19 pitch would gain some rpms. the boat is a 1986 formula f3 and has lived on a trailer in the garage always.

 

[icyb]

Have tried trim in and all the way out, tabs all the way up. The timing is at 8 and advancing past 12. But I have no way to check total advance.

 

[Maclin]

The slip% with that High5 is what is bugging me, still thinking about it.

 

[Faztbullet]

A 5 blade is not a speed prop..

 

[jimmbo]

I think the factory propping of 21 was a bit optimistic. A 19 would have been more realistic on a heavy 21 footer with a 1.5:1 drive.
What altitude is the lake you go to, versus the altitude of Erie?
Have you checked to see if the throttle plates on the carb are opening fully when the throttle lever is pushed all the way to ‘go-go’?

 

[icyb]

I think the factory propping of 21 was a bit optimistic. A 19 would have been more realistic on a heavy 21 footer with a 1.5:1 drive.
What altitude is the lake you go to, versus the altitude of Erie?
Have you checked to see if the throttle plates on the carb are opening fully when the throttle lever is pushed all the way to ‘go-go’?

I know the secondaries are opening, I will check the throttle plates next time on the water. A coworker has a spare prop 3 blade ,he's not sure on the pitch. My gut feeling is a 3 blade 19 pitch might put me in the middle of the range.on lake Erie we seldom can run wot for a minute. Most of the time on a good day 3000rpms and on the really bad days maybe 12 to 14 mph. The small inland lake is only 200 feet higher that's all. I don't want to lug this engine and top end is not my goal.

 

[icyb]

This is a deep heavy boat,plus all my fishing gear and it has a 107 gallon tank.

 

[icyb]

Just seeing if i can post bigger pics.

​

 

[icyb]

Well after I got the hi5 blade off this morning and finding out it had a lock on it.i found the key it looks like a socket. I put a friend's spare never used prop 14/1/2 19 pitch 3 blade aluminum. And I could spin 4500 and 43 mph. Merc said 4200 to 4600. So what do you guys think I should do now.buy the same prop ,same size but go with ss. And your professional thought on using the hi5,remember with the hi5 I'm hitting 4000 rpms. Want to thank you guys .

 

[porscheguy]

See if you can find a used mirage plus in 19P. Make sure it’s new enough to have PVS.

 

[Sea Rider]

How many souls and gallons of fuel were on board when tested your friend's 19 prop while revving at 4500 wot rpm ?

Happy Boating

 

[icyb]

A friend and i and about half tank 50 gallons. . Im thinking a 17 pitch would go over on rpms,not sure.

 

[Sea Rider]

Check if can stay with your friend's 19 prop or buy same new. Is already working very well in the upper side of the wot rpm range with 2 up, can include an extra soul on board and engine will rev around middle wot range. As more fuel is consumed from 1/2 tank wot rpm whether middle or max will increase accordingly.

Just for the record, check with 3 up and report max achieved wot rpm to see how much rpm drops adding one more soul on board.

A 17 pitch will over rev badly that engine unless plan boating with more souls and more gallons of fuel on board to compensate that if like boating at full hammer down. If with 2-3 up, that 19 works very well.

Happy Boating

 

[icyb]

Check if can stay with your friend's 19 prop or buy same new. Is already working very well in the upper side of the wot rpm range with 2 up, can include an extra soul on board and engine will rev around middle wot range. As more fuel is consumed from 1/2 tank wot rpm whether middle or max will increase accordingly.

Just for the record, check with 3 up and report max achieved wot rpm to see how much rpm drops adding one more soul on board.

A 17 pitch will over rev badly that engine unless plan boating with more souls and more gallons of fuel on board to compensate that if like boating at full hammer down. If with 2-3 up, that 19 works very well.

Happy Boating

Very good info will try as you suggested, thank you.