Carb Spacer Questions

[Jason Johnson]

On a hot rod carbed outboard what is the typical expectation when adding a set of carb spacers?

[mackeral5]

jason- joe raimondo (dingie2) made a set of phenolic spacers for his yamaha v4 and they didn't work out. if memory serves me correctly the carb signal either became irratic or it dropped too low to pull fuel. maybe he will see this post and chime in. the merc guys seem to report midrange improvements, but no clue on a 3cyl yammie...hopefully someone will chime in.

[Dingie 2]

It didn't work out on the V-4 Yamaha,air speed was WAY slow killed bottom end . Throttle took forever to respond. I had a 1 inch set between carbs and intake. Complete waste of time on the combination that I ran. Joe Raimondo

[ChrisCarsonMarine]

Jason,from what I can tell and guess the spacer plates for the v6 mercs improve the angles in the intake to allow more direct access to the whole reed block by the fuel/air mix coming into the motor.It also increases the volume of intake area before the reeds,I dont know where the benefit comes from.I personally haven't heard anything about carb spacers in 25 years,some people user them on small motors years ago,but I have no idea if they really helped,talk to T Rex,he's worked a lot with spacers,I think.Stay warm,chris

[Jason Johnson]

Well I have made them, 3/4" I was told to do so by some 3 cyl Johnnyrude folks. Another test I guess, Thanks.

[T-REX]

Jason, I haven't put one on a mota(v-6) yet that didn't show improvement on bottom/mid(especially midrange punch)...I have a 1-1/2" one on Baitcasters 260, and it is very crisp, and runs quite well(but iz a efi mota).....I have made 1" spacers that have went behind the carbs, and spacers tha go betewwn the manifold and reeds...The one that goes between manifold and reeds give more ov a performance gain...

I built a 1" spacer for a Vert reed 2.0, and it wouldn't git outta it's own way!!...

I've made them bigger on tha inside than tha reed cage(thank'in it mite speed up air flow thru tha reeds)...NOT.....I find that if tha same size iz held from the manifold to the reed cage, it shows more gains...I also find that if ya stuff the manifold to git rid ov dead area's, and keep the manifold volume az close to the carb opening(rear) az possible, it also yields a better perf gain...

I have installed spacers on several 2.4 chrome bores, and one ov the three would require diffrent jets in tha idle's, while the others required no change...How ever if U stuff the manifold, U will have to tune each cyl az to it's own needs(top end and idle)...Also your reeds/cages play a big part ov how much gain/loss U see with a spacer, but I ain't goin ther, kuz it's winter time, and tha cyber henchmen are lay'in in wate, wait'in ta jump!!:D

[sschefer]

Hey T-Rex, what ya worried about... You just skin'm and eat'm anyway's LOL....

Good info on the spacers.. I've found that just measuring for a spacer if I was to think about using one leaves me with a problem in the cowling.. No room. I'm running 98 EFI upper and lowers on my carbed 91 and even then I'd be in for some grinding. I think an Alien would be necessary wouldn't it?

I think a lot of guys look at the spacers and think they'll be good but don't think about the other changes they may need to make and good cowlings aint cheap. You have to ask if it's worth it or not.

[Rigaud]

I have been looking into carb spacers and I have a V-4 Yamy 115 coming apart this month. What T-Rex mentions is what I have been thinking that it might hurt it on the bottom end. Having an even flow from carb all the way through to the reeds is important. Otherwise if you end up with turbulant air bouncing around on it's way to the cylinders it will slow things down.

I'll know myself what to do once I have the powerhead on the bench in my shop and I'll post what I find.

[Dingie 2]

We already made tested and junked a set of 1 inch spacer on a V-4 yamaha. If you still think you want to build a set E mail mackeral 5 I think he may have the set I had made,you will also need to replace the black plastic cam that opens your carbs and if you have oil injection you will need to extend the rod from your carbs to the pump one inch.Joe R
I have been looking into carb spacers and I have a V-4 Yamy 115 coming apart this month. What T-Rex mentions is what I have been thinking that it might hurt it on the bottom end. Having an even flow from carb all the way through to the reeds is important. Otherwise if you end up with turbulant air bouncing around on it's way to the cylinders it will slow things down.

I'll know myself what to do once I have the powerhead on the bench in my shop and I'll post what I find.

[T-REX]

I've found that just measuring for a spacer if I was to think about using one leaves me with a problem in the cowling..

Baitcasters 260 sports a mid 90's stock 260 cowl, and had room for 1-1/2" spacer...I haven't run into any room(or lack ov) problems with any hipo type cowls...Fish'in cowls, yes, they are shifted further back to make room for the large regulators and coils mounted piggyback to regulators...I thank U could run a 6" spacer in a allien cowl..:eek::D...

Oh, I did run into a lil cramp'in in tha Chrysler cowl wit a 1" spacer:D


you will also need to replace the black plastic cam that opens your carbs and if you have oil injection you will need to extend the rod from your carbs to the pump one inch.Joe R

Also there's also all bolts have to be longer than stock...the mounting bolts, az well az the reed cage bolts...

[mackeral5]

rigaud- I've got the yamaha v4 spacers Joe R made, they are somewhere in my boxes of junk. let me know if you want me to find them.

[Dingie 2]

Mike has the spacers and I have the extended oil pump rod and black plastic cam that worked. All you will need to get would be 8 carb mount bolts 1 inch longer than the stock bolts.QUOTE=mackeral5;1871175]rigaud- I've got the yamaha v4 spacers Joe R made, they are somewhere in my boxes of junk. let me know if you want me to find them.[/QUOTE]

[Rigaud]

OK but is it worth it or you just have them around and want to get rid of them? Thanks in advance for the info and offer.

[mrcrsr]

we produce them for the merc v6, and it is a part you can actually feel the difference from, ours bolts between the reed cages and intake manifold(or reed plate) on the v6 engines. i'd like to think it would be worth your trouble, at the end of the day an engines an engine no matter what the color paint is, it firstly straightens the path for the intake charge, secondly it creates a tunnel ram effect for the charge(just like a v8 w/ a tunnel ram, you can probably lengthen the linkage that goes to the cam to get it to work

[Darkside's Calling]

I know the space is tight in my V-6 Yamie cowl (Excell powerhead in a V-6 Special cowl). I had to run the short Excell tapered carb hat as the better flowing V-6 Special alloy one wouldn't clear. If you V-4 is as close as the V-6's it's gonna be TIGHT!!!

[mrcrsr]

I know the space is tight in my V-6 Yamie cowl (Excell powerhead in a V-6 Special cowl). I had to run the short Excell tapered carb hat as the better flowing V-6 Special alloy one wouldn't clear. If you V-4 is as close as the V-6's it's gonna be TIGHT!!!
how about losing the airbox?

[Rigaud]

Well, thanks to Jason who started this thread seems we got some good info here so far. I already measured and theirs plenty of space for a 1" spacer with lots of free space left over in my V-4. Air box can even stay on so it can remain looking stock. I'll probably make it myself since I have experience as an R&D machinist.