Gear ratio? Help for 72 rude

[mostlysnow]

Can anyone tell me if there is a difference in gear ratios of 72 evinrude 25 horse? it is in a fiberglass terry boat 16 footer. (Heavy I know)
I had to fix bottom end and before doing so I was able to bring front end up now it wont do it like it used to was wondering if by some chance put wrong ratio in. Now a pontoon can race me to the other end of the lake that is bad...LOL takes me fifteen minutes just to go three miles.
Unfortunately I don't have the old gears to compare teeth on each. Could I need to replace the prop itself?
Also while I am here can anyone tell me where all the screws are that can be adjusted to get more ummp out of the motor I can only find the lean rich (this I have adjusted 1 1/2 turns out) mixture screw and linkage adjustments.
One last question for this thread...my linkage wont put throttle all the way full is there an part of adjusting I might be missing, I have taken the control box apart to make sure linkage cable was ok and looked at where it hooks up to motor everything looks fine ...my handle on motor itself turn throtle full but the controler up front does not. Is there a vacum assist on this kind of motor?
I know this sounds like a lot but any help will be apreciated Thanks to all that reply.

 

[jimmbo]

Re: Gear ratio? Help for 72 rude

12:21 is the gear ratio.
The throttle cable should be adjustable for travel at the motor end. Perhaps the inner wire of the cable has slipped in regards to the set screws on the casing guides(one at both ends of the cable).

 

[R.Johnson]

Re: Gear ratio? Help for 72 rude

Disconnect the remote throttle cable at the engine. put the shift lever in forward, and see if the carb is going full open, and the mag plate is going to full advance using the throttle handle. What size prop are you using? I have one of those small displacement 25's. I found that you need the RPM's up in the 5000+ range to get them to perform. I use a 9x9 on a 14 ft. jon boat to get into this range, and this is a light boat.

 

[F_R]

Re: Gear ratio? Help for 72 rude

There is only the one mixture adjustment and that is to be adjusted for smoothest idle. The high speed jet is fixed and no adjustment can be made to it.

 

[mostlysnow]

Re: Gear ratio? Help for 72 rude

Thanks for your info...I was wondering about the jets being fixed and that is why they might be behind some protective type plugs.
The Lean/Rich mixture knob it is to be adjusted only while in idle mode correct? And not in gear right? I took the adjusting linkage off once to make sure the turns were set right and they are set at 1 1/2 turns then put linkage back on...I can run motor with all the way in lean and rich with no noticable change...why is that do you think? It is jsut hard to start either way. Thanks again hope I can help someone like you have helped me.

 

[mostlysnow]

Re: Gear ratio? Help for 72 rude

Disconnect the remote throttle cable at the engine. put the shift lever in forward, and see if the carb is going full open, and the mag plate is going to full advance using the throttle handle. What size prop are you using? I have one of those small displacement 25's. I found that you need the RPM's up in the 5000+ range to get them to perform. I use a 9x9 on a 14 ft. jon boat to get into this range, and this is a light boat.

I removed remote throtle linkage from motor end and used the motor throttle handle and the thingy does indeed go full distance or advanced whatever it is doing. Without hooking remote throttle cable back up I move throttle levers forward as if it was hooked up then looked at the differenc in distance there is about 1 inch more needed to make throttle go the full distance BUT my linkage is already fully adjusted out no more to play with is there a way I can makea adapter to make cable go further and then have some adjustment?
My prop is a 8' prop and my ratio I found to be a little under two turns of flywheel for one full revalution on propeller, I was just readiung somewhere the ratio could be a 1.98 to 1 something or other...and if you look at a reply I received it is suppose to be 12 something ratio why the discrepiancy do you think? I want to thank you for your help too everyone needs help and you guys know what you are talking about sounds like...hope some day I can help some one too. Thanks again.

 

[mostlysnow]

Re: Gear ratio? Help for 72 rude

12:21 is the gear ratio.
The throttle cable should be adjustable for travel at the motor end. Perhaps the inner wire of the cable has slipped in regards to the set screws on the casing guides(one at both ends of the cable).

You are saying my engine should turn about 12 turns for one turn of the prop??? I turned the flywheel after marking the teeth and the prop and it is showing almost two turns for one of the prop how come? As for the cable I think your info on the cable is great but can the cable itself be too short?
Thanks for your help

 

[jimmbo]

Re: Gear ratio? Help for 72 rude

12:21

prop turns 12 times for every 21 turns of the engine


You say the remote throttle lever goes as far forward as it can but the lever at the engine is still an inch from wide open? How far back(towards slow) can you pull the remote lever back? Also does it keep moving even after the lever at the engine has stopped?

 

[Chinewalker]

Re: Gear ratio? Help for 72 rude

Your gear ratio did not change and cannot be changed. There was only ever one ratio offered for them. The 12:21 (1.75) ratio is very close to two turns of the flywheel for one turn of the prop. The ONLY other gear ratio offered in that style gearcase was a 15:26 ratio (1.73) which was virtually the same ratio. They offered that in the 1950s but determined the finer teeth didn't stand up well and went to the heavier teeth of the 12:21s....

Bottom line - the issue is not your gear ratio...
- Scott

 

[mostlysnow]

Re: Gear ratio? Help for 72 rude

Your gear ratio did not change and cannot be changed. There was only ever one ratio offered for them. The 12:21 (1.75) ratio is very close to two turns of the flywheel for one turn of the prop. The ONLY other gear ratio offered in that style gearcase was a 15:26 ratio (1.73) which was virtually the same ratio. They offered that in the 1950s but determined the finer teeth didn't stand up well and went to the heavier teeth of the 12:21s....

Bottom line - the issue is not your gear ratio...
- Scott

Glad to hear that the bottom line the issue is not my gear ratio that is a relief I was worried I put wrong ones in Thanks for the good news.

 

[mostlysnow]

Re: Gear ratio? Help for 72 rude

12:21

prop turns 12 times for every 21 turns of the engine


You say the remote throttle lever goes as far forward as it can but the lever at the engine is still an inch from wide open? How far back(towards slow) can you pull the remote lever back? Also does it keep moving even after the lever at the engine has stopped?

with remote throttle cable conected to engine and pushed all the way "full throttle" and "in Gear" it is still one inch from being in actually full throttle position acording to the mag plate thingy (the thing that pushes the throttle butterfly on carb) and without remote hooked up the engine mounted throttle handle turned to "full speed" mag plate advances to full as it should.
Second part of question about the "slow range" well it closes the butterfly completely as for the one moving more then the other I have not noticed but will check for you soon and inform you on results.
Can a cable be too short just wondering, it seems I have extra slack between motor and throttle and gear selector control box.

 

[Chinewalker]

Re: Gear ratio? Help for 72 rude

Those older throttle controllers have set-screws that attach the cable ends to the bowden wire within the cable. Those screws can slip, or, if a previous user has broken the wire, may have been reset closer to the barrel nut enough to prevent full extension. You obviously have an issue somewhere within the throttle system and not at the motor end, so start there. If you can't adjust it out of the system by resetting the set-screws, you may need, at minimum, new bowden wire, and possibly a new cable....
- Scott

 

[mostlysnow]

Re: Gear ratio? Help for 72 rude

Ok, I want to start off by saying thanks to all who have helped me so far and here is a update:

We (You and I) now know my ratio is fine (thanks for that info ), we (You and I) worked on my cables and figured out it was indeed the set screws (thanks for that info ), we, now have a boat that runs but we have incountered a problem...

Ok I was tinkering with cables and setting idle and such, And I noticed my water pump might not be working now. I have had this motor in a 50 gal trash can (did not run for long just long enough to set idle and see if will restart easier, and in the lake and I am pretty sure it was working up until tonight. (Now I will be honest with you, I did and do start motor up before putting in the water just for a few seconds to make sure it will start... the line to get into the lake can be long sometimes and I want to make sure I don't hold up the rest that is why I do it. Is this wrong?)

Correct me if I am wrong...The water goes in a plate of holes just above trim plate right? and suppose to come out at or near top of the housing that houses the "drive shaft" (what do you call it a shaft housing??) or is it suppose to come out the exhaust hole at bottom of said housing just above the propeller?

So what I am asking now after reading other posts here on the webpage where can I get a pump kit, for this motor? I have a boat shop or two in my area but I am kind of affraid they might rip me off, So any ideas suggestion would be appreciated.

Thanks again for all of your help in the past present and future

One more thing I was looking around for parts came across some motors with thermostats,Does mine have one? Could mine be sticking and if so where is it located?

 

[Chinewalker]

Re: Gear ratio? Help for 72 rude

Was the water level at or above the bulge between the exhaust housing and the gearcase housing? Needs to be that high to prime the pump (as it would be when sitting at the dock on the boat).

If you do not know when the waterpump impeller was last replaced - replace it. Period. Even if it "looks" okay when you remove it.

Your motor has a t-stat, but it should pump something whether it is open or not. It is not an all or nothing system. You can get the impeller right here on iboats. Part number 18-3002 for the impeller alone. Might have to go to a dealer to get the complete kit if your housing is shot.

- Scott

 

[rickdb1boat]

Re: Gear ratio? Help for 72 rude

Grab one of these too...

http://www.iboats.com/Seachoice_Pro...831964324--list_time.1180709829--view_id.4612

And for exploded views of your motor:

http://epc.brp.com/login.aspx?ReturnUrl=%2fdefault.aspx%3fbrands%3dej%26lang%3dE&brands=ej&lang=E&AspxAutoDetectCookieSupport=1

 

[rickdb1boat]

Re: Gear ratio? Help for 72 rude

Thermostat is #19

 

[jimmbo]

Re: Gear ratio? Help for 72 rude

Grab one of these too...

http://www.iboats.com/Seachoice_Pro...831964324--list_time.1180709829--view_id.4612

NOT!!!

Muffs will not work on a 1972 25hp. The water intake on that engine is on the front of the exhaust snout behind the prop. A barrel is the best way to run this type.

 

[rickdb1boat]

Re: Gear ratio? Help for 72 rude

Good catch Jim....Thanks...

 

[mostlysnow]

Re: Gear ratio? Help for 72 rude

Was the water level at or above the bulge between the exhaust housing and the gearcase housing? Needs to be that high to prime the pump (as it would be when sitting at the dock on the boat).

If you do not know when the waterpump impeller was last replaced - replace it. Period. Even if it "looks" okay when you remove it.

Your motor has a t-stat, but it should pump something whether it is open or not. It is not an all or nothing system. You can get the impeller right here on iboats. Part number 18-3002 for the impeller alone. Might have to go to a dealer to get the complete kit if your housing is shot.

- Scott

Hey, thanks for helping me so far, You asked if the water level was above or at the buldge between gear housing ..answer yes. I kind of figured it would need primed...as for you saying about iboats selling me a water pump kit I looked at the Cata log and found one but wanted to see if I could get one sooner then 5 day or more.without paying arm and leg in shipping, just getting anxious I think want to hit the water hard this year haven't been able to for a few now. Now as for knowing if housing is shot or not how will I know? I mean will there be obvios signs?
Well thanks again for your help I am sure I will have more questions as this episode plays out...till next time thanks

 

[mostlysnow]

Re: Gear ratio? Help for 72 rude

Grab one of these too...

http://www.iboats.com/Seachoice_Pro...831964324--list_time.1180709829--view_id.4612

And for exploded views of your motor:

http://epc.brp.com/login.aspx?ReturnUrl=%2fdefault.aspx%3fbrands%3dej%26lang%3dE&brands=ej&lang=E&AspxAutoDetectCookieSupport=1

I can open top link but not the bottom one why do you suppose?(My computer must have had a mind of it own I can get it now saved it in my bookmarks this alone will come in handy when trying to tear boat motor apart LOL) As for the muffs they will not work on my boat unless the water inlet is some place other then where I think it is...mine if I am not mistaken is just above trim plate it is on the left side looking from back of motor and there is a small inch tall four inch long peice of metal with few holes in it, I was thinking this was my inlet ( am I wrong?) Thanks for your help now and in the future