Seasonal lower unit swap

[mac_in_mt]

I have just recently purchased my first boat! The boat is a 1981 Hewescraft River Runner with a 115hp Mercury (early 1990's) that has been converted to a jet. I purchased this boat with the intent of using it mostly in the fall for hunting on the river but have recently rediscovered how much fun it is to fish out of a boat. Being as I want to use the boat on lakes in the spring and summer for fishing I am considering buying a prop lower unit and swapping the lower units out for the different seasons. My questions to the group are:

1. Is swapping lower units out on a seasonal base a feasible consideration?
2. Will I need to install a jack plate on the transom to lower the engine for use with the prop?
3. How much time will it take to swap (I've seen anywhere from 20 mins to 3 hours)?
4. In general how much would a lower unit purchase cost?
5. And finally, any tips or comments?

Thanks everyone for your help!
Pete

 

[TilliamWe]

Re: Seasonal lower unit swap

What will be the advantage, to you, of a prop drive?

 

[Silvertip]

Re: Seasonal lower unit swap

Prop drive is far more efficient than a jet. Unless you have real skinny water to run in and prop damage is likely from submerged object, there is no reason whatsoever to run a jet and be faced with this additional work. If you are familiar with the water, avoid the nasty stuff.

 

[Texasmark]

Re: Seasonal lower unit swap

The other thing is that the Jet is much deeper than the prop like 7" difference (per the Merc Service Manual for current mid-range engines). So the midsection for a Jet would be like for a 15" transom while the midsection for the prop would need to be 20", so not only do you have to swap the lower unit, you have to swap the midsection also to use on the same height transom.

You are asking for a lot of trouble, expense, and possibly breaking something in swapping. I'd leave it be.

Mark

 

[mac_in_mt]

Re: Seasonal lower unit swap

The main reason I was looking at doing a seasonal swap was for more efficiency during the summer when I am fishing. I definately need the jet during the fall and winter for duck hunting. Just last week I was hunting up a side channel and when I was done I discovered the lower end had frozen over. I tried to gently ease myself through the ice but found it was too thick. So I took a run and went over the ice.....something I wouldn't be able to do with a prop! Anyway, I just thought that maybe with a transom jack and a prop I could run further for fishing in the summertime on the same amount of gas.\

 

[Tacklewasher]

Re: Seasonal lower unit swap

I'm still considering what you are thinking about. I picked up a used jet for my motor, but have never installed it. My plan was to use it in the fall fishing the Fraser River but I have not been able to get down there for a couple of years so have not installed the jet.

Pretty sure a jack plate is needed. The two setups need to run at different depths. I have one from my last boat.

No idea on the midsection. I know mine is fine as is but it's a different application.

I need to get a longer control cable for the gear shift. It has to reach the jet instead of just under the cowl.

 

[TilliamWe]

Re: Seasonal lower unit swap

The main reason I was looking at doing a seasonal swap was for more efficiency during the summer when I am fishing...\

While a prop drive is more efficient, I highly doubt you'll ever use the boat enough to pay for the cost to swap it! Plus one busted prop or propshaft and you'll have spent 10x the amount of extra gas you'll use with the jet.
My official advice is:

Use it as is, and don't think twice about it.