Cylinder head swap 115 V4

[TurboJet]

Afternoon all,

As always looking for an "upgrade" I have seen others swap to high compression heads versus low comp heads

The heads on my V4 currently are 326505 and 326504 and am looking at a set of 324322 and 324321 which supposedly came in an "upgrade kit"

Am i correct on the 322 and 321 heads being the high comp heads?

Are the gaskets different?

Will i need to adjust anything more on the engine or is it pretty much swap-n-go?

Being i have the powerhead on the workbench, the $ is buring a hole in my pocket

Thanks to any pointers

 

[TurboJet]

I think I have answered my own question about the heads being the higher comp heads by looking at them side by side.

I can see the 324322/321 heads have a half donut shaped combustion chamber "filler", in which would shrink the combustion area making it higher compression?

Is there anything I would need to do in terms of fueling?

I have read about "jetting up" my secondaries in the carbs, but can't verify the jets needed...

I am premixing my gas, inline fuel pump, and run the 1-5/16 carbs

Any input is appreciated!

 

[boobie]

Edit..........Wrong post.

 

[TurboJet]

Any input on the subject boobie?

I am curious if I can just swap the hi comp heads and go!

Thanks and any input is appreciated!

 

[boobie]

Not sure how much but you may have to change some carb jetting and maybe timing.

 

[TurboJet]

Thanks for the reply sir

I went ahead and picked up the heads 342322/321 online and will post pics if anyone is interested

I also picked up an entire 115 powerhead to tinker with on the workbench at a great price, the heads will prob go on it after a teardown

The "upgrade kit" also speaks of a "muffler upgrade", but Mrs. Linda at turbojetmarine products thinks the only difference in the muffler is a restrictor in the brass fitting for the water line coming from the heads...She believes it keeps more water in the heads.

I can just put a reducer in-line to prob mimic the implementation.

I thought about entertaining a 140 powerhead swap, but unsure of the complete ramifications to the jetdrive unit/specs/ect/ect

Here is a link to the head kit if anyone is interested

http://turbojetmarineproducts.com/w...ojet-Cylinder-Head-and-Muffler-Kit-437826.pdf

 

[racerone]

What year 140 powerhead ?

 

[TurboJet]

I was thinking a mid 90's looper

I have read good things about those

There are a few at some of local boat yards in pieces

 

[racerone]

The 140 looper is a totally different block and will not fit on your adapter plate of the crossflow.

 

[TurboJet]

Hmm, well good to know!

Thanks for that...

Looks like a late 70's model then, but I haven't really researched all the things involved (as you can tell) !

It's really just a thought since the 140 is the same "package size" to fit in the rear of the boat

 

[racerone]

The older 140 HP blocks were prop rated.---So no more power than the 115 HP block in a turbo jet.----

 

[TurboJet]

Thanks for the tips!

Excellent info

Looks like head a swap and maybe some reed upgrades are about all I can squeeze out of the 115?

Maybe some velocity stacks on the carbs? ha!

Thanks again for the replies, much appreciated.

 

[jimmbo]

The older 140 HP blocks were prop rated.---So no more power than the 115 HP block in a turbo jet.----

I think you meant the older(1977 - 1984) 140s were crank rated.

 

[jimmbo]

Thanks for the tips!

Excellent info

Looks like head a swap and maybe some reed upgrades are about all I can squeeze out of the 115?

Maybe some velocity stacks on the carbs? ha!

Thanks again for the replies, much appreciated.

Your 115, I will assume it is a jet? Just out of curiosity, what year is it?
Looking at the "upgradekit",

Do the heads look like

old ones

new ones

.

 

[TurboJet]

Thanks for the reply jimmbo

Yes, my configuration is a jet pump (omc turbojet)

1994 -- 115JEER

And yes, the heads old and new look like your pictures

I am pretty sure, the later "turbojet" engines came with the heads pre-installed from factory or it was "an option", not sure which really

The early 94/95 owners had the option to "buy the upgrade kit"...

Thanks again!

 

[TurboJet]

Hi again jimmbo , did you have any more input on the heads?

As stated above, the pics look like the two differences in heads.

Also noted is, I called Mrs. Linda again at turbojetmarineproducts, and she informed me she has installed many of the"head upgrades" without messing with the timing or carbs...

She only recommended using certain Champion spark plugs and running 91 octane would "be better" but not necessary.

Anyone with more input on the subject I would be more than happy to hear your input as these heads may just go on the powerhead I am running now.

Thanks!

 

[jimmbo]

The plug she recommended is probably a colder plug. The 91 octane requirement... The higher compression heads, of which there are several versions, were used on the 1973 - 1976 135hp, the 1977 - 1984 140hp, and in the post 1984 110, 112, and 115 hp motors. As the years progressed the compression ratio was lowered slightly. All engines were marketed as being able to run on regular gas. Gasoline has changed a lot over the years, even if the octane numbers are the same. Swapping heads shouldn't raise the octane requirement above what was a stock engine. However there may have been slight changes to the piston deflector during the years as the heads were changing, and some combinations could be more prone to detonation. Chances are you aren't going to hear any pinging or knocking with the outboard like you do in a car or truck engine
Jetting was often richer so as to cool the piston, mainly to prevent detonation. Once the new heads are on you might want to richen the carbs at first, then after reading the spark plugs, try leaner jets

In your second post, you mentioned "jetting up the secondaires". The carburation isn't staged so there aren't any secondaries. The carbs may have an idle jet, a midrange jet and a hi speed jet. Is that what you were referring to?

 

[TurboJet]

Hello again sir and thanks for the reply...

About the carbs, that is correct...Sorry about my lack of knowledge on certain aspects of the engine, this is my first boat and I am learning alot!

Before this, I have never seen a "V4" and thought it was a wild sight!

Also with the carbs on the opposite side of the heads was a sight as well!

About the jets, I would like to enrichen and do some carb testing, but I am unsure on where to get "jets"...

I have rejetted my suzuki samurai carb, so this i feel comfortable with

Where would one find larger/smaller jets?

iBoats sells them?

Any baseline jetting you suggest?

Thanks again, this has been much help!

 

[jimmbo]

Before this, I have never seen a "V4" and thought it was a wild sight!

Well the V4 was first marketed in 1958

Also with the carbs on the opposite side of the heads was a sight as well!

They pretty much have to be to have a place for the reeds, and to provide a straighter path for the air-fuel mix to pass through as well as better exposure of the connecting rod for lubrication

About the jets, I would like to enrichen and do some carb testing, but I am unsure on where to get "jets"...

That's the 'not so easy' part. OMC didn't offer much when it came to changing carb jetting. Probably saved a lot of engines from owners wanting to improve economy.

Where would one find larger/smaller jets?

Going through the carb parts lists of many engines that use the same basic carb bodies is one way. Often dealers have scrap piles of carbs, maybe that's a source. Online outboard performance sites?

iBoats sells them?

If the jets are shown to be available

Any baseline jetting you suggest?

4 or 5 steps richer, then work leaner from there, but never go leaner than stock

You said your engine was a 115 jet, it has the bulge on the exhaust cover, between the cylinder heads?

 

[TurboJet]

Yes sir, 115 bubble-back exhaust

Thanks for the other tips/advice in the above post