170 transom

[sicilian slam]

Can the transom of an early model 170 be closed off and a jack plate added to give a little more space? I am concerned that extending the motor another foot or more off the back of the boat is going to make it sit a lot lower in the water. Also repowering the boat. It is a 73 rated for max 85hp. Is it ok to put a 115? Thanks.

[RickK]

Hi SS,
I've mentioned this several times on this site but never found the topic I posted it in again - there was a 170 at the engine rebuilder where I got my 115/90 from.  It had the aft closed in, a bracket on it and a 150 (I think suzuki) sitting back there    I talked to the rebuilder about it and he said it was a buddy of his and that he had warned him that there was too much weight back there but the guy didn't listen.  He got it all ready and took it on it's maiden voyage - the guy said it jumped out of the hole like none other and was flying.  When the guy came off plane he did it a little too fast and the boat sunk right on the spot.  
My boat has a 90/115 on it and while the freeboard is a little low, it handles it fine on the original transom. I say 115 because that is what I bought from the rebuilder and I say 90 because that is what the mechanic said it is (only difference is the jetting in the carbs).  There are members here with 125s, 130s and 140s.
There was one member who wanted to put twin 70s on his 170 with a full transom and bracket so he could drive it over to the bahamas - so members warned him against it that I think we scared him off and we haven't seen him around here since.  We weren't so woried about the weight but the trip.  He probably went forward with his plan - seemed pretty convinced of it's merits - hope it went well for him and he's still alive.

[c master]

I have a '76 170, with a Johnson 88 spl. Based on the floor drains when the boat is at rest, it would seem to float slightly lower (1" ?) than designed.  I have 'ping pong ball' valves over the drains, but I doubt the AS folks expected they would be necessary in 1976.

Re: the engine:  I would just want to know the actual weight of whatever engine you are considering.  Compare that to the weight of what you have now.  Personally, I wouldn't want any additional weight back there beyond what I have.

In your case, I am guessing that the added weight of the jack plate, combined with the added distance from the transom, is going to be too much for a 170, especially when two 'bigger' people are back there.

I'm of the opinion that the 'cut down' transom is a safety feature...theoretically, the deepest water could get in my boat while underway is limited by the height of the lowest point of my transom.  Add the raised area up forward (about the same height as the 'cut away') and my boat shouldn't be able to hold that much water.  A higher transom would change this dramatically and (IMHO), make the boat less safe.





These little boats perform so well, it's easy to forget that they're only 17' long.

[akbridge]

I have a CMC jackplate and a 90 hp on my 170.  I have had no major issues with water over the transom.  Just a splash or two.  My boat feels a little light in the bow to me.  I would not extend anymore weight over the rear than needed.  I do not think there are any gains to hanging an engine that far off the back.  A light weight 115 would not be an issue with the boat.  You will not gain a lot of speed with a 115 over a 90.  I can get about 39 mph with my 170 while Rick gets 40.

[bandaidmd]

cmaster,
"I'm of the opinion that the 'cut down' transom is a safety feature...theoretically, the deepest water could get in my boat while underway is limited by the height of the lowest point of my transom. Add the raised area up forward (about the same height as the 'cut away') and my boat shouldn't be able to hold that much water. A higher transom would change this dramatically and (IMHO), make the boat less safe."

I have been thinking of ways to leave the motor where it is and also block the water from spashing over the transom but your thoughts on the safety aspect are valid points i had not thought of. I think i will just keep my little blidge pump back in the corner and not worry about changing anything.