New project '80 100hp - seeking info

[iwombat]

Well I just picked up a Johnson '80 100hp w T&T and a stainless prop for $150. That '80 cover with the javelin badges sure looks nice, it's in good shape too. It's got a ticking noise and bad compression in one hole, so I'm figuring it probably needs a tear down and at least one hole redone. I'll do all the bearings and stuff too while it's all apart. Fortunately, it came with a full powerhead gasket set, so that's a good bit of savings too.

Anyway, I'm planning on getting into this over the winter. In looking over the engine parts lists, from what I see the 100 and 115 share everything but the carb jets. Is that right? Looks like the 100 has bigger mids and smaller mains. Since I'm tearing this apart, I'm wondering what I can do cheaply to bump this up a bit. I'm thinking bubble-back exhaust if I can find one cheap, and boyesen reeds to start with. Is the bubble-back a direct bolt on, or are there other mods that need to be done? Any other ideas?

 

[iwombat]

Re: New project '80 100hp - seeking info

bump

 

[iwombat]

Re: New project '80 100hp - seeking info

bumpity bump bump

 

[iwombat]

Re: New project '80 100hp - seeking info

bump with bump sauce

 

[ezeke]

Re: New project '80 100hp - seeking info

Pretty sure you have to machine the block to do the whole bubbleback if it is flat now, unless you can do it by leaving out the exhaust filler blocks. You better check with DHadley to see if that is OK for the engine.

The engine can run as a 115 on the flat exhaust and if the ports are the same. I think you might just want to find a later set of carburetors from a 115, though.

 

[emdsapmgr]

Re: New project '80 100hp - seeking info

Your 100 crossflow will respond well to some mods. Pretty much the same as the 115. You have the choice to bolt on parts, or do machining work. Some bolt on mods: Check the carb flange faces. The better carbs are those that have the 1 5/16" throats. The 140's used those. Get a set of early 140 heads. Add the intake filler blocks from the 140 -322684. (some older 115's had them.) I like the composite reeds and have had good luck with them. The engine will idle better and improve midrange. Maybe even a some extra revs on top. If you want to teardown and get into machining mods, you can port the intake and exhaust. Also, you can put the bubble back exhaust on, but technically, you have to deck (machine) the block exhaust area to make sure it is flat after you bolt the exhaust fillers in. It may not be worth the expense. Current power packs limit revs to 5800, so you might look for a pair of the old (used) original packs. I'd suggest you consider boring all holes and new pistons. The bores and pistons wear with age, and some of the noise you hear could be piston slap from wear. Good luck with the project.

 

[iwombat]

Re: New project '80 100hp - seeking info

Thanks for the suggestions. Knowing me, I don't think I'd ever bore one hole and leave the rest. It's fun to entertain the idea that I could though I'm pretty certain that the noise I'm hearing is piston slap and not any lower-end issues.

I'll make a note to measure the carb throats and see what I've got.

What's an "early" 140 head? 1978-?? (or something else).

Sounds like the bubble-back is a nice idea, but may be more effort than payback. I'm not looking for a screamer, but a 115hp or better once I'm done is really what I'm shooting for. With that in mind, I'll probably forgo the machining mods and stick with easy bolt-ons.

So, it's looking like carbs, intake filler blocks, reeds and heads is on the shopping list for now.

 

[emdsapmgr]

Re: New project '80 100hp - seeking info

The early 140 heads: 322864, 865. Ran for 4 years 78 into 81, when they changed. The 125 and 135 heads are good, but don't have the coil supports. You'd have to make a bracket for each coil to attach to the head.