1985 mec 115 lower unit

[ono_55]

Hi,new here, what lower units will interchange with my motor?
Thanks.

 

[Texasmark]

Re: 1985 mec 115 lower unit

Probably the 70/75 hp area up through the biggest tower of the day. I had an 85 and a 115 of the vintage and the gear housings seemed to be the same size as I recall. The operation of the LUs was identical. The only variation would/should be the gear ratio. The higher hp engines (115 & up) tended to run 2:1 whereas the little guys ran the 2.3:1. Makes a 2-4" difference in the prop you would run.....more pitch with the 2.3 for the same job requiring the same hp.

Mark

 

[ono_55]

Re: 1985 mec 115 lower unit

Mark, do you have any idea what years would bolt up to my powerhead?

Jim

 

[Droll]

Re: 1985 mec 115 lower unit

ALL inline 6 Mercury and Mariner lower units produced between 1973 and 1988
( + some others ( including some inline 4 engines, but they might use a different gear ratio .)).

You can use the older straight skeg and the newer back swept skeg lower units..... all these lower units are 2:1 .


Arne Kjetil

 

[Texasmark]

Re: 1985 mec 115 lower unit

ALL inline 6 Mercury and Mariner lower units produced between 1973 and 1988
( + some others ( including some inline 4 engines, but they might use a different gear ratio .)).

You can use the older straight skeg and the newer back swept skeg lower units..... all these lower units are 2:1 .


Arne Kjetil

I seem to recall when I was shopping for my '89 115 seeing a 90 hp spec in that sales brochure that showed it to be the same engine but the rpm upper limit was about 500 lower and the gearbox was 2.3. I remember that because their ad was pushing the torque of the 90. I wondered why change the lower unit ratio and remember assuming that the 90 was built for heavier work at lower top speeds and the 115 for hauling butox.....which mine did nicely.

My current 90 3 cyl is 2.3 as is the 75 (of the same model/year timeline which shares the same block and lower unit). The higher hp 4 cyl engines all had the 2.0.

So, just pay attention ono so that you can get it propped right whatever it is. You can tell by just putting it in F gear and rotating the driveshaft through 720 degrees. If the prop winds up in the same place it's 2:1. if you have to turn the shaft an additional 90 degrees (108 actually) to get it back where it was you have the 2.3.

Mark

 

[Droll]

Re: 1985 mec 115 lower unit

I seem to recall when I was shopping for my '89 115 seeing a 90 hp spec in that sales brochure that showed it to be the same engine but the rpm upper limit was about 500 lower and the gearbox was 2.3.

The engine i question are a 1985 115hp a inline 6 engine ( Direct Charge ), the 1989 115hp are a inline 4 engine ( Looper ) a different animal ...

Last year for the classic inline 6 engine was 1988 .


Arne Kjetil

 

[Texasmark]

Re: 1985 mec 115 lower unit

The engine i question are a 1985 115hp a inline 6 engine ( Direct Charge ), the 1989 115hp are a inline 4 engine ( Looper ) a different animal ...

Last year for the classic inline 6 engine was 1988 .


Arne Kjetil

Yeah, I keep hearing that about the last year of the tower, but I bought one on a Ranger BB and it was ID'd and Texas titled as a 1989 (and I assure you it was an arse hauling 6 cyl), as was the boat, both new, purchased from a long time, large volume, reputable dealer in Dallas. I have no way to dispute what you said about when it may have been physically constructed, but it was marked and sold as I said.

Mark

 

[achris]

Re: 1985 mec 115 lower unit

Yeah, I keep hearing that about the last year of the tower, but I bought one on a Ranger BB and it was ID'd and Texas titled as a 1989 (and I assure you it was an arse hauling 6 cyl), as was the boat, both new, purchased from a long time, large volume, reputable dealer in Dallas. I have no way to dispute what you said about when it may have been physically constructed, but it was marked and sold as I said.

Mark

Mark,

It's not unknown for boat builders to stockpile engines. They get offered a good deal on the last of a line and will buy it out. They may have the engines in stock for months, or even years, before fitting them up to a boat.

We had one builder in Perth who bought up the last of the Mercruiser 90's and 110's. They finished in the early 60's, he was still fitting them to new boats in the late 70's!!!

As was said earlier, the in-line 6, 115hp finished in 1988. The 1989 115 was a 4pot, 2+2 engine (only ran on 2 cylinders at idle and up to about 1800 rpm).

For the OP, any of the old inline-6 and inline 4 (except a 50hp) gear boxes.

Cheers.

 

[ono_55]

Re: 1985 mec 115 lower unit

Thanks guys for all the info,so from all the info all inline 6cyl well work and some of the 4cyl. What year 4cyls well work.

Thanks again
Jim

 

[Texasmark]

Re: 1985 mec 115 lower unit

Mark,

It's not unknown for boat builders to stockpile engines. They get offered a good deal on the last of a line and will buy it out. They may have the engines in stock for months, or even years, before fitting them up to a boat.

We had one builder in Perth who bought up the last of the Mercruiser 90's and 110's. They finished in the early 60's, he was still fitting them to new boats in the late 70's!!!

As was said earlier, the in-line 6, 115hp finished in 1988. The 1989 115 was a 4pot, 2+2 engine (only ran on 2 cylinders at idle and up to about 1800 rpm).

For the OP, any of the old inline-6 and inline 4 (except a 50hp) gear boxes.

Cheers.

While you are here, Mr. Achris, I really, really like your Bertram. That is one beautiful, well performing, finely crafted, craft that obviously performs as well as it looks and is built. Congratulations on your purchase!........BUT YOU KNEW THAT! That's why you bought it. Grin

On the disable 2 on the later Merc 4 bangers I think that totally sucks. Personal opinion. One reason I bought Mercs, especially the tower I had, was the smooth idle you get with all those ponies kicking in. I never had one of those 2 + 2's, but I had engines of 1 and 2 cylinders and compared to the tower, even the old 4 cyl, they were rough.

Mark