Help needed to mod a 1980 Johnson V4 85hp

**71V153** · 06-25-2017, 05:39 PM

Originally Posted by 58Evinrude

Ya got me curious enough to go check my 115. Its a 91, not mid 80's like I thought. And the exhaust is cut. Just have to pull the reeds out and see if there are stuffers in there. Any idea just what sort of hp I might be able to make from this? I have an early 80's 115 on my Winder now, I know its really a 90 in prop hp.

Well a solid 115hp if nothing else?

**71V153** · 06-25-2017, 05:44 PM

Originally Posted by 58Evinrude

Ya got me curious enough to go check my 115. Its a 91, not mid 80's like I thought. And the exhaust is cut. Just have to pull the reeds out and see if there are stuffers in there. Any idea just what sort of hp I might be able to make from this? I have an early 80's 115 on my Winder now, I know its really a 90 in prop hp.

I'd expect the boat to be 3 - 4 mph faster with a prop rated 115 vs crank rated.

**FMP** · 06-25-2017, 05:54 PM

5hp=1mph You figure in this range

**71V153** · 06-25-2017, 06:09 PM

Originally Posted by FMP

5hp=1mph You figure in this range

~55 with a 90. ~63 with a 140. Stock motors on a Baja 15SS.

**58Evinrude** · 06-25-2017, 06:29 PM

I get 55 with the old 115, I had it to 65 with a mildly worked 140. And when my brains fell out, it did 76 with a 235.

**olboatman** · 06-25-2017, 06:54 PM

Did all the 140s come with a 2to1 gear LU....as I would think thats where the next big mph gain would be?

Gary

**58Evinrude** · 06-25-2017, 07:09 PM

I think they did. But I also think that a V6 1.85 gearcase will bolt on.

**71V153** · 06-25-2017, 07:30 PM

Yup 26:13. Reckon that's 2:1?

**71V153** · 06-25-2017, 07:33 PM

Granted a V6 case will expand yer propportunities. But there's plenty of good V4 props out there.

**58Evinrude** · 06-25-2017, 07:50 PM

Well, since most of my stuff is for V6's, its a change I will make

**71V153** · 06-25-2017, 08:19 PM

Originally Posted by 58Evinrude

Well, since most of my stuff is for V6's, its a change I will make

Just remember that gearcase is larger and displaces more water than the V4. Requiring more hp to push it as fast.

**spybot** · 06-26-2017, 02:14 AM

Originally Posted by spybot

Ok guys gathering all the info needed for my build. But and its a big BUT
Should i Square of the ports r just leave them as is?
If i leave them as they are Should i remove the "Tits"
Some say Square some say Leave

Can we get back on to this please guys

**spybot** · 06-27-2017, 02:12 AM

Originally Posted by racer

The ports are double drilled to make each port which leaves a tit in the middle. IMO only remove these and not square the ports, engine will live much better and not have a big power difference. The more you do the more fuel you need to add. It will also need 91 octane or higher fuel and timing set to the heads used.

Ctr bottom of block machined to open block to exhaust bubble better.

OK Racer your are the author of the report i will be basing y transformation round so i will be taking your advice on this. It may work it may not work. I have read a few people doing the 9 pages to a V4 so there is a chane but mine will be built to be a fast reliable lake boat. You never know we could be setting a new way forward ie a 5 or 6 page for the Non Racers out there. I hope i can bend your ear on a few things?
Cheers