Evinrude 150 cylinder head swap

siestadave

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Jun 26, 2010
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Hello , long time viewer, first time poster. Great site btw.
Wondering if any of the engine gurus here could answer a quick and easy question. And a pre-thanks to the ones that do.
I have a 1987 Evinrude 150tlcur. Recently it has been overheating.
changed thermostats
changed water pump
changed grommet
No difference
Pulled heads (part # 328324 and 328325) and found deflectors to be swollen and some gunk in the water jackets. Replaced the deflectors and removed the gunk.
At that point figured i would pull the head covers off and clean any material lodged in there as well........Arghhhhh....All the heat i could use and still the old bolts were snapping.

Now my question. My neighbor has a pair of heads in his garage parts # 332 544 and 332 545.... I have found one small post on the internet stating that these will fit....and a later post saying that these are even better..
If I replace with these heads will I need to re-jet the carbs or change the timing. Or will the be a direct plug and play replacement.
If re-jet and or timing is involved would anyone know what size jets. and which way on the timing.
Thanks a ton
 

emdsapmgr

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Dec 9, 2005
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11,551
Re: Evinrude 150 cylinder head swap

Yes, those heads will fit. They are off a 150S GT/XP model. They will be higher compression than your originals. You may notice slight hp improvement when you next go out. If you do go with these heads, you may want to jet the mains up one or two jet sizes to keep it running cool. Leave the timing where it is. If you could also find a matching set of GT/XP carbs they will bolt right on. These have larger venturis and will make more hp and are made to run with those heads.
 

siestadave

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Jun 26, 2010
Messages
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Re: Evinrude 150 cylinder head swap

Awesome!!!
Thanks a ton for the reply. I will grab the heads today ( already have all the gaskets ) . bolt them on and see how it goes. My neighbor has a ton of engine parts in his garage that were left by the previous owner. Ill have to dig through and see if there are any carbs in stashed in the boxes. ( gt/xp ).
Much appreciated :)
 

emdsapmgr

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Re: Evinrude 150 cylinder head swap

The good GT/XP carbs are the 1 5/16" carb throats-the same as used on the early 175 and 200 crossflows. Check the carb throat size on the front flange of the carb. The 150 GT/XP engines were closer to 165 horsepower.
 

siestadave

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Re: Evinrude 150 cylinder head swap

Just an update. I swapped out the heads.Fired right up..Ran her for about three hours. Pulled the plugs a few times. All looked to be burning correct. I really appreciate the replies.
As far as the gt carbs...Im gonna pester my neighbor when i see him.. Ill check for flange and let you all know....Thanks again....Im also posting a binnacle question on a new thread. If you all wanna chip in again... :)
 

siestadave

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Messages
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Re: Evinrude 150 cylinder head swap

Hello, it's been a while. I have been enjoying my boat since the last time your wisdom helped me get back on the water.... I had swapped out my heads with gt150 heads... At the time I was advised to look for some gt150 carbs to get a bit more power from my engine.....I have finally found a set with the correct throat size at a local swap meet......will rebuild and install soon. My question for this next task is...

Do I need change the intake? Or the reeds or both.... Is it beneficial at all, or are the stock ones fine or exactly the same?

Again, thanks for your help
 

emdsapmgr

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Re: Evinrude 150 cylinder head swap

GT/XP carbs will bolt right on and should run well as is since you have recently put on the XP/GT heads. The intake does not have to be changed-it's the same for all hp models. I would suggest you pull the intake off and install some intake filler blocks. (one per cyl.) These are good for 5-8 hp on a V6. 322722. Found in the 1979 200/235 engines and other high hp models. (Not the same part as the
V4 filler blocks.) They are NLA, but there are still many around in marine salvage yards. A set of composite reeds would also be a good addition to the engine. They make the engine idle better, and have good mid range pickup. You might get 100-200 rpm on top.
 

siestadave

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Jun 26, 2010
Messages
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Re: Evinrude 150 cylinder head swap

Again, many thanks.
Ok so the carbs being a direct bolt , should I increase jet size? Or will the standard ones from the gt carbs be sufficient?

Reeds? Boysen? Or any recomended brand that you would suggest? And is it that much of a benefit to ditch the old reliable ones that have been in there all these years?

The filler blocks? From the 200/235? No problem for the 150? And no other adjustments or parts to compensate?

Thanks
 

emdsapmgr

Supreme Mariner
Joined
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Messages
11,551
Re: Evinrude 150 cylinder head swap

GT/XP 150 carbs will not have to be rejetted if that's the only change. The filler blocks will fit just fine with no further changes. I've had good luck with the Boyesens and think they are a great addition. If you do convert to the Boyesens, they will come with instructions for a carb jetting change. They flow more air (that's good) so follow the included installation instructions and make jetting changes accordingly.
 
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