Is going from 115hp to 140hp worth it?

**Spaceman Spiff** · 06-12-2023, 11:32 PM

The boat is a 17' Larson 1100lbs. I have a 1983 Mariner 115 on there now and I can get a 1980 Mercury 140 for probably only a few hundred bucks after a swap. I haven't really tried to dial in a prop and motor height on this boat yet and I'm hitting around 41-43mph. I imagine it's basically the same motor with just more fuel and exhaust flow. Both say 300lbs. Is the difference in hp significant enough to do the swap? Keep in mind that I love working on my boats. I'm always looking for more excuses. LOL I know a V6 150hp is probably better suited to my boat, but can't find those in my price range.

Stephen

**David** · 06-13-2023, 12:03 PM

The question is complicated because in 1983-1984 Mercury transitioned from crankshaft HP to propshaft HP ratings. My guess is that there is little difference between a 1983 115 and a 1980 140. There might still be some inline 6 gurus around here who will know more.

**LakeFever** · 06-13-2023, 12:25 PM

Nope not imo. Make the leap to a v6 its another universe of performance

**derekfl** · 06-13-2023, 05:30 PM

the one advantage of buying the 140 is you now have 2 motors instead of one. running 40 year old extinct motors requires at least 1 spare...

**Spaceman Spiff** · 06-13-2023, 09:38 PM

Thanks for all the input.

How can I determine if my 83 Mariner is prop or crank rated?

**Will hedrick** · 06-13-2023, 10:06 PM

My question is what is the boat rated for

**pcrussell50** · 06-13-2023, 10:19 PM

Originally Posted by David

The question is complicated because in 1983-1984 Mercury transitioned from crankshaft HP to propshaft HP ratings. My guess is that there is little difference between a 1983 115 and a 1980 140. There might still be some inline 6 gurus around here who will know more.

1977-1990 V6's are the hot ticket imho, and the 150's seem to be the most common. The are not the newest carbureted generation. The 1991 and later V6's fill that bill, and they are more expensive. The 1977-1990 V6's are MUCH cheaper, and yet almost as good as the newer ones. As long as you are staying carbureted, I don't think you give up much (a little maybe, but not a lot), and it's a great deal cheaper, to go with a mid-80's V6.

I'm not on Facebook so I can't check their market place, but I just checked Portland and Seattle Craigslist. Didn't find any today, but mid-80s v6 150's do pop up fairly frequently. the same engine is available as a 2.4/200 too, but those don't come up too often from the bay area down to socal.

-Peter

**Spaceman Spiff** · 06-14-2023, 09:04 AM

Originally Posted by Will hedrick

My question is what is the boat rated for

150 on the plate

**derekfl** · 06-14-2023, 10:49 AM

Mercury started downgrading the in-line six a little bit after the V6 came out in the late 70s. So sometimes it wasn’t really downgrading it so much is making the number read lower should a V6 looked more attractive. I don’t think there’s really any difference between 80 140 and an 83 115. Is this buying an extra motor? Or is the swapping your motor that you already know and trust for another motor that you don’t really know anything about. If you’re getting a second motor it’s different.

**derekfl** · 06-14-2023, 10:51 AM

There are in-line 6’s all over the place for sale. Nobody is buying them. Except people that already own one and want another one for spares.

**LakeFever** · 06-14-2023, 11:22 AM

Cdi type Inlines are great motors but the V6 is where its at. A cheap carb 2.0L 150 will be a substantial step up from a 140 inline and way more potential. The prop selection alone makes it worthwhile. The 2.0L v6’s get excellent fuel mileage at 30mph cruise too

**pcrussell50** · 06-14-2023, 02:16 PM

Originally Posted by LakeFever

Cdi type Inlines are great motors but the V6 is where it’s his ^^^at. A cheap carb 2.0L 150 will be a substantial step up from a 140 inline and way more potential. The prop selection alone makes it worthwhile. The 2.0L v6’s get excellent fuel mileage at 30mph cruise too

^^^this^^^

After my sloppy word salad that somehow got a couple of likes

I want to take another crack at explaining:
The 80’-‘90 v6’s were amazing, and by now much cheaper than the ‘90’s V6’s.

As to the 90’s ones being better… There was a race-biased thread here about that, where one of the racers said that the 90’s 2.5/200hp almost always beats the ‘80’s 2.4/200 in racing. I just don’t know if you or I as recreational/family boaters will be able to tell much difference. And I can’t imagine anything easier to maintain than the ‘80’s V6’s. Then again, there is so much physical similarity with the the ‘90’s V6’s that maybe they’re just as easy to maintain? :shrugs:

-Peter

**derekfl** · 06-14-2023, 03:59 PM

I think carbs are a bit simpler and ignition more modern and durable. Merc did more with porting in at least some of the 2.4’s. I think they got more conservative with the 2.5. To the point that the 2.4 will put out more power than a 2.5 that is stock. The 4% difference displacement difference is less than the near 10% weight diff. But you can’t throw a 30 buck parts store hone in those chrome bores and a set of rings and say good enough. And most of us only use full throttle for a few seconds to make sure motor will hit full rated rpm and then pull back to 1/2 to 3/4 power to travel.

**pcrussell50** · 06-14-2023, 04:12 PM

Originally Posted by derekfl

I think carbs are a bit simpler and ignition more modern and durable. Merc did more with porting in at least some of the 2.4’s. I think they got more conservative with the 2.5. To the point that the 2.4 will put out more power than a 2.5 that is stock.

interesting. Do you think that applies to the November 1990, “black Welch plug” blocks that you and I have? Pretty cool, if so.

-Peter

**derekfl** · 06-14-2023, 04:15 PM

It also seems that the v6 is still commanding a premium price in the Pacific Northwest. Down here in the gulf southeast they can be had under 1k running and driving. And 2-300 in repairable shape. The Tower is near free everywhere. Even a motor that is 10 years younger than an early black max. Almost tempted to set up a pipeline st ship some of these to the northwest.