Please help.

[Mjordon]

I just purchased a 15hp mariner that the guy said was a short shaft, but upon investigating I found out it's a long shaft about 25" I was looking to find a 12/14ft aluminum boat, any idea how long the transom would have to be in order for my motor to push it decently

 

[JimS123]

A long shaft is 20". I don't believe there is a 15 HP outboard made that has a 25" shaft. Its likely you have a short shaft and are measuring from the wrong position. Google OB shaft length, cavitation plate (anti-ventillation plate) to get a picture of the components.

A short shaft should measure ~15" from the transom clamp to the aforementioned plate. You don't measure to the bottom of the motor.

 

[airshot]

Yep have to agree here, mabey a 20 " as they are readily availiable but a 25" is rare unless you have the sailboat version then many of those do have a 25" leg. But they are geared differently to push a large sailboat with a high thrust prop, not a good choice for a 12-14ft rowboat.

 

[Mjordon]

Thanks for the info guys. I called mariner customer service to find out the year an they said its a 1991 15hp mlh which he said was a long shaft. I believe I am measuring correctly from top of motor mount to the fin right above the prop. An it's measuring about 24 25. Can I post a pic on here. Would that help any

 

[bonz_d]

I would trust Mariner/Mercury that it is not an extra long shaft for a sail boat. 20" transom should work just fine.

 

[roscoe]

No Title

Sure, post a photo.
Post the model number too.

 

[Mjordon]

Model number 0d058613 and if I got a boat with a 16" transom could I build it up to make it fit a long shaft with a 25" shaft

 

[Mjordon]

How can I find out if it's for a sailboat? I'm pretty sure it's a 25" shaft. The guy a
I bought it from said he had it on a dingy, but he also said it was a short shaft. I just want to get out on the little rivers here

 

[JimS123]

You already have determined that its a long shaft. Just buy a long shaft boat. There are as many long shaft boats these days as there are short shaft boats. No, you cannot build it up. That would cost as much and require so much effort that you will be cheaper to buy the right boat.

 

[Mjordon]

Thanks Jim. So if the shaft is 25" long how long should the transom be?

 

[Mjordon]

Pic

 

[GA_Boater]

Thanks Jim. So if the shaft is 25" long how long should the transom be?

I'm sorry, but are you reading the replies? Here is a chart to determine what model you have. From Merc in Post #4 - MLH - Manual start, Long shaft (20"), H is tiller.

Buy a boat with a 20" transom.

 

[Bondo]

Thanks Jim. So if the shaft is 25" long how long should the transom be?

Ayuh,.... If it's a 25" shaft motor, ya need a 24/ 25" transom,....

If it's a 20" motor, ya need a 19/ 20" transom,....

If it's a 15" motor, ya need a 15" transom,....

 

[fhhuber]

While its possible to extend a transom up to deal with a longer shaft outboard... its not as simple as just bolting on a chunk of plywood and 2X8 for thickness (seen that done...)

You sandwich the extension between 1/16 aluminum plates... and add triangular bracing. How much bracing depends on the HP and how much extension was needed.

The bracing may need to extend QUITE a bit forward...

I've seen it actually done right ONCE.

 

[shrew]

Look closely at the outboard. There is more than likely just a 'long shaft' extension on the lower unit. You should be able to turn that back into a short-shaft again. that would make more sense than trying to build a 'wall' on the transom to accommodate the wrong sized outboard. Or sell/trade for a properly sized OB.

 

[Mjordon]

Yes your exactly right mr shrew. But would that require me to buy a lower end shaft. Or can you just remove ext. i

 

[Mjordon]

I was thinking about just selling the 15hp. I found a 2002 smoker craft with a 20hp Suzuki. When and looked at it yesterday but we couldn't keep the motor running. It would start for a few seconds with starting fluid then cut off. Also the primer bulb was not getting hard. And when I pull started it gas was shooting out the carb. But when we used electric start no gas was shooting out? Really like to know if this is a easy fix before I spend 2 grand

 

[shrew]

Yes your exactly right mr shrew. But would that require me to buy a lower end shaft. Or can you just remove ext. i

You're going to need to buy some parts. Still easier and a much better idea than trying to re-engineer the boat. Your other option is to sell what you have and buy a properly sized OB.

 

[bonz_d]

I was thinking about just selling the 15hp. I found a 2002 smoker craft with a 20hp Suzuki. When and looked at it yesterday but we couldn't keep the motor running. It would start for a few seconds with starting fluid then cut off. Also the primer bulb was not getting hard. And when I pull started it gas was shooting out the carb. But when we used electric start no gas was shooting out? Really like to know if this is a easy fix before I spend 2 grand

Haven't worked on any Zukes but that sounds like it needs a good carb cleaning which isn't a hard job. Also one shouldn't use starting fluid in a 2 stroke. It's very hard on the pistons and rings. If you can, do a compression test on it. If that checks out good the rest is a relatively easy and cheap fix.

If it won't start and run then make them an offer for that condition of repair.