Mercury 80hp 1969 Lower unit interchangeable with ?

[rob619]

I have a 1969 Mercury outboard lower unit bad on my 80hp mercury. What motors are these foor interchangeable with? Any help pics post any help at all it good. I was told that there was a lot of Expects Mecury guys on this website. I have also included pictures of my motor.. Payed a 1000 dollars for boat and motor and the foot is bad.. The motor runs and idles good. But the foot does not work.

 

[Maxz695]

Re: Mercury 80hp 1969 Lower unit interchangeable with ?

welcome to iBoats forum i,m sure someone with knowledge of this engine will help you out soon hang in there

 

[chum1]

Re: Mercury 80hp 1969 Lower unit interchangeable with ?

Need more info. on what it does or doesnt do,Looks like a well maintained engine from the outside "and" with tillt trim, check the easy stuff first:

1) shift linkage on l/h side

2) if its jammed in forward it could be an easy lower end shift linkage alignment problem

3) is there any oil in it?

4) if last service on impeller is unknown you may want to read up and pull lower end or have someone else do it.

5) make sure to grease lower end splines when it goes together, they will rust.

 

[Wingedwheel]

Re: Mercury 80hp 1969 Lower unit interchangeable with ?

Like Chum was saying, give us some more info along with a serial # for your motor.

 

[79Merc80]

Re: Mercury 80hp 1969 Lower unit interchangeable with ?

In general, The 650 (65hp), 800 (80hp), 900 (90hp), 1150 (115hp), 1250 (125hp), 1350 (135hp), 1400 (140hp), 1500 (150hp), all use the same lower unit, although some have a different gear ratio. But, that can be fixed with prop pitch to a point.

Hope this helps.

Craig

 

[rob619]

Re: Mercury 80hp 1969 Lower unit interchangeable with ?

Chum and others the serial number is 2561944... The lower unit is not good it had water in it when we undid the oil screw. It has a crack in the lower unit where the tread would be on the lower unit the prop part attached to it can be pulled out.. I have to replace the whole lower unit. What is a good price for a working one... I have some one it has one for 300 dollar with no impellar he siad he takes them out so makes you have to put a new on in it... It was pumping water and running idle be for we took the lower unit of.. I took it of in neutral I hope I did that right...

Thanks guys for all the help... I hope to find one that good price before June.. Would like to take with us on vaction in June.

Robert

 

[rob619]

Re: Mercury 80hp 1969 Lower unit interchangeable with ?

What years are it compatible with... And what is prop pitch.. Sorry first boat with a motor other then trolling motor

In general, The 650 (65hp), 800 (80hp), 900 (90hp), 1150 (115hp), 1250 (125hp), 1350 (135hp), 1400 (140hp), 1500 (150hp), all use the same lower unit, although some have a different gear ratio. But, that can be fixed with prop pitch to a point.

Hope this helps.

Craig

 

[Gomer50]

Re: Mercury 80hp 1969 Lower unit interchangeable with ?

The 650 (65hp), 800 (80hp), 900 (90hp), 1150 (115hp), 1250 (125hp), 1350 (135hp), 1400 (140hp), 1500 (150hp), all use the same lower unit..The gear ratio on your lower unit would be a 2.3 and I would guess a 13 1/4 x 15 pitch prop.The bolt up patern is compatible with lower units up until the early 80's however 85hp and up used a different gear ratio.If I am not mistaken all the way up to 115hp used a 2.1 gear ratio,which will work on your motor.You will have to drop your pitch size to make up for gear ratio difference.I used a lower unit off of a 115hp motor and had to drop my pitch size down to a thirteen to stay within the 80hp rated rpm which is 4800 to 5300 rpm.For a good lower unit $300.00 isnt to bad.A new impellar is a given (cheap insurance on the motor).Do yourself a big favor and make sure you are running that motor within your rpm range @ WOT.I am sure someone will chime in on how to explain pitch on a prop.In general once you get your motor up and running and put her in the water to test you will see what rpm @ wot you have.Lets say @ wot(wide open throttle) you are running with a normal boat load 4800 rpm you would be at the bottom of your rpm spec's. With a 15 pitch prop (guessing) and you would lets say drop to a 13 pitch prop you would gain approx. 400 rpm. which would put you at 5200rpm you win.

 

[rob619]

Re: Mercury 80hp 1969 Lower unit interchangeable with ?

The boat came with two props.. one small and a little lighter then the other one.. I guy that had the lower unit siad he would trade my old one for one that work and put it in for 250 if I brought the impellor.. I can bet that then right... And he siad he would make sure it in good working order be for he lets me live with it..

The 650 (65hp), 800 (80hp), 900 (90hp), 1150 (115hp), 1250 (125hp), 1350 (135hp), 1400 (140hp), 1500 (150hp), all use the same lower unit..The gear ratio on your lower unit would be a 2.3 and I would guess a 13 1/4 x 15 pitch prop.The bolt up patern is compatible with lower units up until the early 80's however 85hp and up used a different gear ratio.If I am not mistaken all the way up to 115hp used a 2.1 gear ratio,which will work on your motor.You will have to drop your pitch size to make up for gear ratio difference.I used a lower unit off of a 115hp motor and had to drop my pitch size down to a thirteen to stay within the 80hp rated rpm which is 4800 to 5300 rpm.For a good lower unit $300.00 isnt to bad.A new impellar is a given (cheap insurance on the motor).Do yourself a big favor and make sure you are running that motor within your rpm range @ WOT.I am sure someone will chime in on how to explain pitch on a prop.In general once you get your motor up and running and put her in the water to test you will see what rpm @ wot you have.Lets say @ wot(wide open throttle) you are running with a normal boat load 4800 rpm you would be at the bottom of your rpm spec's. With a 15 pitch prop (guessing) and you would lets say drop to a 13 pitch prop you would gain approx. 400 rpm. which would put you at 5200rpm you win.

 

[rob619]

Re: Mercury 80hp 1969 Lower unit interchangeable with ?

Thanks for every ones help on here ! I hope to have it running soon! I will let you guys know when I get it running and make a short vido so you can see the old Merc in action... Thank you all!

 

[evangelistrr]

Re: Mercury 80hp 1969 Lower unit interchangeable with ?

Hey this is rob619 I had to change my user name I could not get the system to send me a user name password email.. So here we go agian.. I have a lower unit know off a 85hp thunderbolt. All bolt line up however it will not go all the way in for me to screw it in to place. The only differnace I can see is a little pin on top of the shaft of the 85 hp which mine does not have. So any one that can help please let me know.