installing updated carbs on older motor

[Chris's CVX16]

Hello,

I have a '79 100 HP Johnson V4 on my boat. It generally runs well but sometimes it's a bit finicky. It's not running right compared to last season. I plan on doing a carb rebuild of the older style carbs I have on her now but was thinking why waste my time and go for an upgrade.

I have a "parts" motor I picked up on Craigslist last year for cheap. It is a 1988 Johnson 88 SPL and it is nearly complete (missing the motor internals). It has the newer primer style carbs (also slightly bigger venturi's). I have the intake manifold if that is different from mine as well as the front plate and cover which are different but I think I am missing the fuel pump and primer solenoid as well as most of the hoses that feed the tiny injection ports. I also have a cracked fuel inlet on one of the float bowls so that will need to be replaced.

Is this a worthwhile upgrade? My motor generally starts fine (unless I touch the priming bulb) but does seem to flood easier than I think it should. I would love better throttle response off idle and more air at wide open wouldn't be bad either. I have ran the larger carbs off the 115's before but took them off because the bushings were shot causing all sorts of air leak issues. Those 1 3/16 carbs ran nice above 4000 RPM but started and idled like crap.

If I do this is there anywhere where I could get a picture/diagram of the fuel hose routing?

I've got pics if needed.

 

[Chris's CVX16]

Re: installing updated carbs on older motor

Friday I noticed I wasn't getting very good flow from my front mounted fuel tank down the copper lines to a fitting on my splashwell and out to the other side of my primer bulb. I think this week I will be replacing all the rubber lines again since it's easy to do and not too expensive. I have decent flow now that I have blown the line out. Before it was a dribble into the gas can and now it is a solid stream. I al also replacing the 2 year old Champion "Q" plugs. Maybe even with the Iridium NGK's .

 

[emdsapmgr]

Re: installing updated carbs on older motor

Your 110 hp engine has more in common with the 115 that year than the 85 hp version in 1979. Putting 88 hp carbs on the engine is probably the equivalence of running your stock 100 hp carbs. Not worth the swap. I'd be looking to upgrade to a pair of 1 5/16" carbs for your engine. They will blow more air and fuel into the powerhead. I'd look for two typed of upgraded carbs: 1. Ones with the choke butterflys. or: 2. Carbs with the small single hose barb atop the two venturis. Also, locate a set of rubber intake filler blocks (NLA) from a 115/140 from that year. 3-5 hp gain. You should see a factory fuel hose routing here: epc.brp.com Just locate your year engine/model.

 

[Chris's CVX16]

Re: installing updated carbs on older motor

Thanks for the info. Since the 88's carbs need one new float bowl it isn't a "free" upgrade.

I'll keep my eye out for possibilities. I'm just hoping that this isn't a carb problem and is related to the rectifier that self destructed last November that I have replaced but am worried that the bad one might have hurt something. The new one makes nearly 17 volts at speed so it's certainly working.