What is difference between different HP powerheads?

[crispins]

I have a 115 right now. What is the difference between that one and an 85 HP?

I guessed that it would be the carbs and exhaust but now am doubting that guess.

Is it intake and exhaust porting?

If I replace my 115 with an 85 powerhead would I then actually have just 85 HP?

 

[F_R]

You have to begin with some details. Year/model?

 

[racerone]

The lower HP blocks as in 88 hp have smaller intake ports.----Exhaust set up is different and machining is required to swap over the bubble back from a 115 to an 88 hp model.

 

[Faztbullet]

Some of the 85hp had a smaller bore depending on year. You need a 1990 up block.

 

[crispins]

Sorry for the lack of details. It was a late night post before going to bed.

I am looking at a 1991 Johnson 88 powerhead to replace my 1998 OMC 115 powerhead.

I am just doing research at this point. I have a May 29th deadline to get my boat on the water so weighing all options at this time.

 

[racerone]

Time goes faster as the weather warms up.-----You " may " not make the May 29 deadline.

 

[crispins]

This is what I am looking at


http://www.ebay.com/itm/Johnson-Evi...b2497a8&pid=100033&rk=3&rkt=8&sd=122433580269

 

[racerone]

I would want to witness a compression test before handing over that kind of cash.--I know that for less than 1/2 that money I get the COMPLETE motor knowing it needs the typical rebuild!!----Complete means lower unit included too.

 

[ondarvr]

You have a couple of threads on this now, and not all the info people need to form a good answer are included in this one, they should be kept in one thread for your benefit.

 

[jimmbo]

There were two totally different 115s in 98, crossflow and looper.

 

[crispins]

There were two totally different 115s in 98, crossflow and looper.

I posted a link to the ebay ad that has the motor listed.

it is all quite confusing to me.

I seriously just want to run out screaming and light the boat on fire.

From what I understand I have a crossflow power head. My boat is a 98 but seems they did not make my motor in 98??? So I would guess that makes my motor a 97.

My research states that the powerheads from 91-97 are all basically the same.

What I would like is to get my boat working ASAP and have it be reliable.

I am trying to figure out the best way of doing that.

I linked a motor on this post, it is not a 115 rated powerhead, so I should pass correct?

I would love if someone could take a bit of time and really give me some good direction.

I have tools, I have some money. I have some time.

Please how do I get this boat going?

It has a great hull and interior. I want to be out on the lake.

Thank you very much..

 

[jimmbo]

My research states that the powerheads from 91-97 are all basically the same.

Your research is that they have the same displacement.
Some, but not all Differences;
Cylinder Heads
Carbs
Exhaust tuning
Reeds
Crankcase stuffers
Engine Block

 

[ondarvr]

This is why it gets confusing when you have two threads going on the same subject.

​In the other thread I said there may be differences in the crank and drive shaft between the 98 and 91, and that you need to check a parts diagram to ensure you can drop the older powerhead on your pump. I also said you will most likely have a difficult time finding a parts diagram for a 98, so check the 96 and 97. It will be the same diagram for the 112 and 115.

​And I also said the diagram may tell you the length of the drive shaft, the longer drive shaft can be shortened, but you can't lengthen one.

 

[crispins]

This is why it gets confusing when you have two threads going on the same subject.

​In the other thread I said there may be differences in the crank and drive shaft between the 98 and 91, and that you need to check a parts diagram to ensure you can drop the older powerhead on your pump. I also said you will most likely have a difficult time finding a parts diagram for a 98, so check the 96 and 97. It will be the same diagram for the 112 and 115.

​And I also said the diagram may tell you the length of the drive shaft, the longer drive shaft can be shortened, but you can't lengthen one.

I did as you suggested and looked at parts diagrams. All I could find was there were different part numbers which could be many different reasons such as crank or rod journel size differences.

Honestly it seems like my hopes of dropping a replacement powerhead are dropping quickly.

I think a rebuild of my powerhead is my best option.

I am thinking a quick and dirty ring replacement is most likely in my future.

I am also taking the advice from this forum (BTW all the advice I am being given I am using) and pulling the head and inspection covers off tomorrow to get a look at what I am working with.

I am thinking after I find out the shape of my cylinders I will start a new thread and that will be the one I stick with.

 

[racerone]

???-----Rebuild the one you have !-----Take it apart and see what it needs first.----You asked and this is " good direction to take "