Powerhead options for a 1989 Johnson 140hp looper

[kai1414]

I'm looking at purchasing a boat with twin 1989 Johnson 140hp looper's on 25" gearcases. The standard roatating 140hp is the one with an "issue". Reportedly it put a rod out through the block. I understand that a reman powerhead is about $2000 give or take, but I'm looking for a diff option, given that my core wouldn't be any good. What I'd like to know is what other year's block's will fit this engine and accept the parts that I already have. I'd rather buy a used powerhead and freshen both of them up myself, but I'm not sure even where to look to know what else would interchange with this outboard. The other think that I would be open to, is a used 140 hp 25" shaft from a similar year with the same engine cid and looper design. Any thoughts??

 

[HighTrim]

Re: Powerhead options for a 1989 Johnson 140hp looper

Those loopers are great torque monsters. Dhadley is definately someone you will want to talk to. Hopefully he jumps in.

 

[Faztbullet]

Re: Powerhead options for a 1989 Johnson 140hp looper

1988-1991 powerheads will exchange and parts are a direct swap.1992-1994 will also work ,but will have to change driveshaft as crank length is different. 1985-87 where small bore with bridged exhaust.. wont work.

 

[Dhadley]

Re: Powerhead options for a 1989 Johnson 140hp looper

Actually the small bore V4's from 85 to 87 will work, no problem. It might be a bit confusing to someone doing the head gasket service later or a complete rebuild. And the cranks and driveshafts will all interchange too. If you use the newer crank with the O ring in the end of the crank it'll just push the driveshaft O ring down. No biggie.

In 92 they went to the newer style hose arrangement on the T-stats and did away with the water control valve. You can actually upgrade any of the 85 to 91's to the newer, much cleaner looking arrangement.

The existing 1989 ignition and carbs will work on any year block. Just make sure you find out what caused the "issue". I wouldn't be surprised if a piston stuck first and then the rod broke or pulled out of the piston.

 

[kai1414]

Re: Powerhead options for a 1989 Johnson 140hp looper

Actually the small bore V4's from 85 to 87 will work, no problem. It might be a bit confusing to someone doing the head gasket service later or a complete rebuild. And the cranks and driveshafts will all interchange too. If you use the newer crank with the O ring in the end of the crank it'll just push the driveshaft O ring down. No biggie.

In 92 they went to the newer style hose arrangement on the T-stats and did away with the water control valve. You can actually upgrade any of the 85 to 91's to the newer, much cleaner looking arrangement.

The existing 1989 ignition and carbs will work on any year block. Just make sure you find out what caused the "issue". I wouldn't be surprised if a piston stuck first and then the rod broke or pulled out of the piston.

Yeah, I'm sure the piston locked up causing the rod failure. I haven't had chance to look personally yet, as I don't own the boat, however most failure's I've experienced in the past were from a similar cause.

So some of the newer 140's will work also? They just have a longer crank and no swap is necessary as its only an o-ring that shifts position? Am I understanding that correctly? Also, the smaller bore block will have less displacement and less power, correct?

One of the things that I had thought about was finding a used block, having the machine work done and rebuilding it myself, however its seems as though that would almost put me in the range of some of the reman. heads. I'm sure those companies get a break on parts that I cant' get as they do it in bulk.

 

[Dhadley]

Re: Powerhead options for a 1989 Johnson 140hp looper

Yes, the newer than 89 blocks will work. The older, small bore loopers will work too. There will be no noticable loss of power on a recreational boat. The small bores had more aggressive port timing & area.

In fact you can take a small bore block and bore it to the newer & bigger bore size. They both have bridged exhaust ports.

 

[reeldutch]

Re: Powerhead options for a 1989 Johnson 140hp looper

thats exactly what i did.

took a 140 1987 small bore and had it re bored to 88 std used the 88 cylinder heads andf used the tstat from the 1993 suffix S mod

im very happy with the power this engine has.
it pushes my 20' mako CC at 6000 rpm with a sst 13 3/4 X 17 to 40mph.

the only thing i would be very anal about is the condition of the block.
they are known to rot in saltwater.

good luck

 

[Faztbullet]

Re: Powerhead options for a 1989 Johnson 140hp looper

I have bored small bore V-6 to newer 3.685 but cutting the camfer in block bottom is a bear..Modifying the pistons wasnt to tough, I went .002 oversize on the lube holes so bribge was lubed and cooler. If you need some small bore blocks got 2 140 freshwater ones..

 

[Dhadley]

Re: Powerhead options for a 1989 Johnson 140hp looper

We quit using the holes to "cool" the bridge. Without holes in the piston it eliminates the V shaped burn mark on the side of the piston. We even use the pistons from the 93 & up V6. The finger port holes in the pistons don't do anything (unless you create finger ports in the cylinder) but the pistons are much lighter. We also use the lighter rods. It's amazing how much better they idle.