Replacement prop, Honda 25

[Wind dog]

Hi Guys
Just got back from a few days at Shasta Lake, what a great place! All went well cept I bent a blade on my prop (Stupid human trick) & my fish finder was acting up, I'll start a thread on thead in Electronics. So I'm checking iboats for a replacement prop but the numbers aren't matching up.
The motor is a Honda 25hp Ser# BAJS-1001827. The numbers on the old prop are, 235x305 & 9-1/4x12.
Can someone help me, iboats is great but their return policy is kind of a PIA so I'd like to avoid ordering the wrong part.
Thanks for any help!

 

[jestor68]

Re: Replacement prop, Honda 25

Honda lists the Solas/Honda 12 pitch prop for that motor as a 9-7/8 X 12. Those props are made by Solas.

Solas lists that prop as a 9-9/10 X 12 in their Brand of props for Honda motors. It's the same prop.

If you desire to replace with the same size prop, order the Solas Amita 9-9/10 X 12.

Adding to the confusion is the fact that Honda lists that 9-1/4 X 12 prop as one of the three "original equipment" on their web site, and now all they list as replacement is the prop mentioned earlier.

My guess is that when Solas took over prop production for Honda, the size(diameter) changed slightly.

Since you are replacing the prop, now might be the time to evaluate the 12 pitch prop's performance and adjust the pitch up or down(if necessary)in order to insure that your motor is operating at peak efficiency.

 

[Wind dog]

Re: Replacement prop, Honda 25

Honda lists the Solas/Honda 12 pitch prop for that motor as a 9-7/8 X 12. Those props are made by Solas.

Solas lists that prop as a 9-9/10 X 12 in their Brand of props for Honda motors. It's the same prop.

If you desire to replace with the same size prop, order the Solas Amita 9-9/10 X 12.

Adding to the confusion is the fact that Honda lists that 9-1/4 X 12 prop as "original equipment" on their web site, and now all they list as replacement is the prop mentioned earlier.

My guess is that when Solas took over prop production for Honda, the size(diameter) changed slightly.

Since you are replacing the prop, now might be the time to evaluate the 12 pitch prop's performance and adjust the pitch up or down(if necessary)in order to insure that your motor is operating at peak efficiency.

Thanks for the response jestor68
Before I start let me say, I know nothing about props. :embarassed:
I am pretty happy with the old prop's performance, my hole shot is a bit slow but I chaulk that up to being a 4 stroke, my top speed at WOT is 25mph (GPS).
I am terrified of chaging props around, I don't have the tools (tach) nore the time & expense it would take.

 

[jestor68]

Re: Replacement prop, Honda 25

A 2.08 gear ratio(your motor's) turning a 12" pitch at 25 mph equals only 4942 engine rpm with a 8% slip.

Since your motor's WOT rpm range is 5000-6000 rpm(25 hp@5500rpm), it appears that the "standard" prop that came on it is not the best choice, because it's not letting the motor turn up enough rpm. That's why your hole shot is pretty slow, as well top speed and ability to carry more load.

If you consider that you need to gain almost 1000 rpm to get your motor up into it's peak power band, we're talking about dropping down at least 2 inches of pitch.

So, I'm suggesting that you purchase the correct pitch prop for your motor, since you're going to buy one anyway. Each inch of pitch changes the WOT rpm by 150-200 rpm.

What type, year model of boat are you pushing with your Honda?

 

[BobGinCO]

Re: Replacement prop, Honda 25

The numbers on the old prop are, 235x305 & 9-1/4x12.

235X305 is the diameter and pitch in millimeters.

235mm = 9.25"
305mm = 12"

 

[jestor68]

Re: Replacement prop, Honda 25

My recommendation for a replacement prop is the Solas Amita # 5211-099-10 ( 9-9/10 X 10).

It will turn the same top speed(maybe slightly more) and provide much more spirited over all performance, as well getting your WOT rpm closer to the ideal 5500.

 

[Wind dog]

Re: Replacement prop, Honda 25

A 2.08 gear ratio(your motor's) turning a 12" pitch at 25 mph equals only 4942 engine rpm with a 8% slip.

Since your motor's WOT rpm range is 5000-6000 rpm(25 hp@5500rpm), it appears that the "standard" prop that came on it is not the best choice, because it's not letting the motor turn up enough rpm. That's why your hole shot is pretty slow, as well top speed and ability to carry more load.



If you consider that you need to gain almost 1000 rpm to get your motor up into it's peak power band, we're talking about dropping down at least 2 inches of pitch.

So, I'm suggesting that you purchase the correct pitch prop for your motor, since you're going to buy one anyway. Each inch of pitch changes the WOT rpm by 150-200 rpm.

What type, year model of boat are you pushing with your Honda?

This motor pushes a mid 90's Valco Westcoaster. It's a 15' tinney. Well for now I ordered the Solas Amita 9-9/10 X 12. When I get ahead a bit I'll get a tach and revisit a hi performance prop, I have way to many irons in the fire at the moment.

BobGinCo, Thanks for explaining the numbers.

 

[Wind dog]

Re: Replacement prop, Honda 25

The new prop came last night, what is the proper "lube" to put on the shaft before installing the prop? Marine bearing grease? Never seize?
Also for the eventual purchase of a higher performing prop could someone recommend a tach?
Thanks & happy Friday!

 

[steelespike]

Re: Replacement prop, Honda 25

I've seen 25 hp motors make over 30 on 16 foot al.boats.
Any lube is better than no lube, someone once said.
If all I had handy was oil I wouldn't hesitate to use it but might check things in a few months.
A light thorough coat of bearing grease is fine.
There are probably a 1/2 dozen induction tachs listed on the net,ebay is one source.
Tinytach has worked fine for people on here. They can be hand held or installed.
The induction tach will work on almost any motor 2 stroke or 4 stroke 1 cylinder or 8 cylinder
land or sea.

 

[Wind dog]

Re: Replacement prop, Honda 25

Thank you sir ;-)

 

[Wind dog]

Re: Replacement prop, Honda 25

I've seen 25 hp motors make over 30 on 16 foot al.boats.
Any lube is better than no lube, someone once said.
If all I had handy was oil I wouldn't hesitate to use it but might check things in a few months.
A light thorough coat of bearing grease is fine.
There are probably a 1/2 dozen induction tachs listed on the net,ebay is one source.
Tinytach has worked fine for people on here. They can be hand held or installed.
The induction tach will work on almost any motor 2 stroke or 4 stroke 1 cylinder or 8 cylinder
land or sea.

I looked into the Tinytach, it looks great. Untill I read that it has a nonreplaceable battery, good for 5+ years. Don't think I want to spend any $ on something I know is going to fail. Even 5 years down the road.

 

[steelespike]

Re: Replacement prop, Honda 25

I looked into the Tinytach, it looks great. Untill I read that it has a nonreplaceable battery, good for 5+ years. Don't think I want to spend any $ on something I know is going to fail. Even 5 years down the road.

There are others out there for less money But I don't have any info on them.
There is also the laser tach though it can be difficult to use on a boat unless conditions are smooth.

 

[Wind dog]

Re: Replacement prop, Honda 25

Man, it looks like Tinytach is the only place that offers a tack / hour meter like this. (small in size w/ didital output, as opposed to a 3-4" round type.) I went ahead and ordered one, guess I'll worry about replaceing it in 5+ years. ;-)

 

[Wind dog]

Re: Replacement prop, Honda 25

Jestor68, you nailed it!
Finally got the tach installed, went out after work to do some testing.

At WOT I'm at about 4500-5000 RPM and 25MPH (The tach jumps quite a bite, I may need to take one wrap off of the plug wire)

 

[jestor68]

Re: Replacement prop, Honda 25

Jestor68, you nailed it!
Finally got the tach installed, went out after work to do some testing.

At WOT I'm at about 4500-5000 RPM and 25MPH (The tach jumps quite a bite, I may need to take one wrap off of the plug wire)

Good; now you have the tool and the basic knowledge to pick a more suitable prop pitch. Have fun!

 

[steelespike]

Re: Replacement prop, Honda 25

Be sure you use a plug wire that will let you keep the antenna wire clear of any electrical interference.
I think you probably want it outside the cover as soon as possible.

 

[Wind dog]

Re: Replacement prop, Honda 25

Be sure you use a plug wire that will let you keep the antenna wire clear of any electrical interference.
I think you probably want it outside the cover as soon as possible.

So would not be a good idea to zip tie it to the existing battery cable harness? ( this would be after exiting the cowling, on it's way to the dash?)

 

[scrnck]

Re: Replacement prop, Honda 25

It might be a bit late but I've read all the info you guys gave, I used to run a 9 .25 x 12 on my 2002 25hp Honda. due to hitting some rocks i decided to go to 9 9/10 x 10 prop due to a very slow hole shot.

I am now extremely happy with the new performance and power of my hole shot.

thanks for the info

 

[Wind dog]

Re: Replacement prop, Honda 25

Hi guys, here's an update.

I'm running a 3 blade Solas Amita 9-9/10 X 12. Unloaded ( Me by myself ) I'm running 25MPH @ 5,000 rpm. With my fishing buddies & full load of equipment I'm running about 17MPH at 35,000 rpm.
So I need to get the WOT's up when loaded? A 4 blade prop? A 3 blade 9-9/10x9?
Help!

 

[steelespike]

Re: Replacement prop, Honda 25

I'm a little puzzled;I wonder why the motor doesn't do better lightly loaded. Is the boat just a bare utility?
If it has floors casting decks and other additions that may be slowing it.
I think you need to have a 10" pitch. Should put you at 5400 Will help with a load.