motor replacement shopping questions

[Thumpbass]

Well I'm looking into options on replacing my '79 100hp Johnson that has a toasted piston...don't want to sink the money into repair so I'm looking into buying something else used to give me a few years of service until I upgrade boats completeley...I need to get a couple of questions answered to be better informed when shopping for a new/different motor

1. Will the mounting holes on a brand other than Johnson or Evinrude fit the holes in my transom or will old mounting holes need to be filled and new ones drilled. In other words, if I get a Merc, Yamaha, Nissan etc. I'm looking at some modifications or will it just mount up as is? Also would motor size make differences in case I had to step down to a 3 cylinder model.

2. Are the older Mercury in-line 4 and 6 motors hard to get worked on? A friend of mine told me that it was hard to find mechanics to work on those and if you did they were much more expensive to have the work done (as opposed to an older OMC).

3. If I found an OMC V-4 or 3 cylinder similar to my motor but was a model without tilt and trim, could I add my tilt and trim unit to it?

Thanks for any info

 

[Kevin W]

Re: motor replacement shopping questions

Question1
No, they are not the same.
Some mid size omc motors have the same mount but i think under 60hp has a smaller mount.
Question 2 i can't say they are harder to find anyone to work on them but IMO they seem harder to tune correctly. At least my old merc 70hp was.
Question 3 i believe alot of the tilt and trim where interchangable between 79 and 91 on the mid size motors 60-115 area.

 

[BoatBuoy]

Re: motor replacement shopping questions

I can't help you with the questions you ask, but there's one question more important than those. Why did the piston on your '79 get toasted? Maybe you know the answer, but without knowing, you risk toasting a piston on another motor.

 

[Thumpbass]

Re: motor replacement shopping questions

I wish I did. I bought the boat last Spring and it ran fine for the first 3 times I took it out. It developed the cough at low idle shortly there after and seemed like a minor issue considering that it was performing seemingly normal in every other situation and hitting the 5000 mark easy at WOT. The mis did seem to get progressively worse....if there was any operator error it was running it at 5000 rpms which I have read here is lugging even though the service manual says 4500-5500 rpm is "normal" and insinuates that anything over 5500 is not recomended. I ran and operated a 1985 15hp Johnson for years with no problems...I know that a 100hp is considerably different than a 15hp but it's not like this was my first outboard. My guess was that it was on it's way out before I bought it and I was a bit too trusting or just un-lucky:/
any thoughts?

 

[Thumpbass]

Re: motor replacement shopping questions

Question1
No, they are not the same.
Some mid size omc motors have the same mount but i think under 60hp has a smaller mount.
Question 2 i can't say they are harder to find anyone to work on them but IMO they seem harder to tune correctly. At least my old merc 70hp was.
Question 3 i believe alot of the tilt and trim where interchangable between 79 and 91 on the mid size motors 60-115 area.

what about this, can you add tilt and trim to a model that doesn't have tilt and trim originally? For instance, I know the old '79 85hp's came in a tilt and trim model and a model with manual tilt....could you ad a tilt and trim system to a manual tilt model?

 

[rickdb1boat]

Re: motor replacement shopping questions

Yes, you can on most models. Either find a used one on Ebay or use an aftermarket unit like CMC or Panther...You would also need the electrics to hook one up...

 

[Thumpbass]

Re: motor replacement shopping questions

Yes, you can on most models. Either find a used one on Ebay or use an aftermarket unit like CMC or Panther...You would also need the electrics to hook one up...

the good news is I still have the tilt and trim unit off my 100 that just blew up...that's why I was asking.
thanks...man

 

[Kevin W]

Re: motor replacement shopping questions

Yes, you can on most models. Either find a used one on Ebay or use an aftermarket unit like CMC or Panther...You would also need the electrics to hook one up...

the good news is I still have the tilt and trim unit off my 100 that just blew up...that's why I was asking.
thanks...man

Well i am not 100% sure but from alot that i have read 79-91 have the same mounting and will fit.
I know this because i had been looking for one for my 85 70hp and all that i read said 79-91 years are interchangable.
At least on 60-115hp range.
if i am wrong someone please correct me..