Adequate engine power

[HeavyDinSC]

The Yamaha 100 four-stroke on my 1983 170 died recently and I'm searching for a replacement engine. I'm curious if any of the more experienced 170 owners out there think a 70 hp will do the job? It's either that or a much newer but way more expensive Yamaha 115.
Thanks in advance for any advice on this topic. 

[boatnamesue]

Depends on what you define as “do the job”....will 70HP get you on plane and to where you want to go...yes. 

Here is a recent post on the matter of 170 power....
https://classicaquasport.com/smf/index.php?topic=15514.msg152768;topicseen#new

[RickK]

Did you check out getting the 100 rebuilt or locate a reman'd power head for it?

[alandry100]

I have a 79 170 with a Yammi 70 2 stroke. I have never run another 170 with anything else but I am fine with the performance. It gets on plane pretty quickly even with load. Tops out around 30mph. If I was on a lake I would probably want the higher end but I am on the ocean and it's usually not very comfortable to go much faster. I fish shallow a lot and like how the boat sits with it.

[cryder]

Once upon a time I had a 17' Osprey with 18 Gallons under the console and a 70 Johnson 2 stroke and it took me water skiing no problem.  IMHO a 70 is just fine with a (can't remember) 15" pitch prop.  A Yamaha 90 would probably be perfect and not require the engine to run at higher RPM.

[HeavyDinSC]

Thanks everyone for all the advice on repowering. Not sure what way I'll go, but I really can't afford a new engine, so I'll keep hunting for a used one. If I can find a 90 or even a 70, I may do that.
In the meantime, if anyone needs parts for a Yamaha 100 4 stroke, but with carburetors (it's not fuel injected), I can help you out cheap.