Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

[Hoop1101]

Hey guys,

I've got a complete 1976 200HP Crossflow (200TL76S) Johnson motor with a bad piston. I found a 1979 235HP (235TL79A) rebuilt powerhead on Craigslist. I've tried to do some research to see if i can swap the powerhead from the 79' to the 76', and all I have been able to find out is that both powerheads use the same powerhead gasket (Part # 323214). So I'm fairly certain they will bolt up. I was just wondering if there were any other incompatibilities I need to be aware of with these two items. I cant seem to find any info online. Thanks!!

-Hoop-

 

[emdsapmgr]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

No. The 200 is a flatback engine. The 235 is a bubble back engine. The exhaust adapters (at the top of the midsection) are different. If you can find a 235 exhaust adapter, you should be able to swap the powerheads. What you are missing is the squarish o-ring that goes under the 235 exhaust adapter. While the powerhead base gasket is the same, the 235 also uses that oring. You will find it on the block parts diagram, just under the back of the engine. Part number: 323625, part #11 on the diagram. If you look at the 235 midsection diagram, you will see there are two exhaust adapters listed, one for all the flatback powerheads and one for the 235- which is what you need. Actually, that 200 powerhead is a pretty unique high perf engine. It is possible it has original factory (uncut) heads. If so, they were the highest compression heads made from the factory for the crossflow V6 engines. Sure you don't want to overhaul that block? If you do go to the 235, you will need larger carbs. The 1 1/4" carbs from the 76 200 are too small to get good performance out of the 235. Likely the 235 may have come with 1 3/8" carb throats.

 

[Hoop1101]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

Thanks for your response! You asked me about rebuilding the 200HP, and I have considered it. The tempting thing about the 235 is that it is ready to go, as it is a complete powerhead with carbs and everything. So it should literally be a bolt up operation. And the price is definitely right. Thanks for taking the time to list the part numbers and the instructions. The only confusion I have is about the o-ring you mentioned. I could not find that part number 323625 on the parts list. I did find #11 on the diagram to be 336429. Is this what you meant?

-Hoop-

 

[racerone]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

The 235 has a fifferent exhaust adapter ( bubble back manifold ) and it is not a direct bolt on fit.

 

[Hoop1101]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

Thanks Racer. Emdsa mentioned that a new exhaust adapter and an additional o-ring would solve it, and so I should have said "almost" direct bolt on. I found the adapter for the 235 online for about $125. I still need some clarification on which square o-ring he was mentioning though.

-Hoop-

 

[racerone]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

Item #11, at least they are installed on my 1982 235 HP motors.

 

[emdsapmgr]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

The oring part number was from the 79 factory parts catalog. Subsequent parts list may show 336429. The 429 is the superceded part number. Same thing. I believe they did away with the rib in the center of the o ring.

 

[emdsapmgr]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

Also, the 235 engines used a unique high perf tuner under the exhaust adapter. All 200 hp and below used the stock tuner.

 

[Hoop1101]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

Thanks again to everyone for the help! I'm learning a lot more about the differences in these Johnson motors. I might have learned too little too late, however. Let me explain. I picked up the "new" powerhead about a month ago. Did the compression check - everything was good. The guy gave me the exhaust adapter and tuner from the old motor. Awesome! I started getting things ready for the swap a couple weeks ago and started noticing that the motor I have, and the diagrams of the 1979 235HP that I supposedly had purchased weren't matching up. Thanks to some advice I found on this forum, I decided to check the welch plug in the top of the block and call BRP with the serial number. They tell me it is a 1990 Johnson 150HP! In disbelief, I started looking up the part numbers on the motor to the 1990 parts catalog. All that I have checked have matched. So now I have this 1990 150HP that I'm trying to fit onto this 1976 Exhaust adapter/lower unit. Gasket looks the same, studs look the same, but the shift linkage on the powerhead is completely different. Cant make it work as-is.

So here is my idea: Take the intake manifold (which the shift linkage connects to), shift linkage, and carbs from the 1976 and swap it to the 1990. I realize I could just change the manifold and keep the 1990 carbs, but I actually like the older carbs better as they seem simpler (mechanical instead of vacuum operated). The intake manifolds look virtually the same except for the shift linkage, but I know looks don't mean everything which is why I'm here. Will the 200 manifold and reeds hurt the "new" motor? How about putting the 200 carbs on a 150? I will try to attach a picture of the 1976 shift linkage. I don't have a picture of the 1990 shift linkage right now.


Thanks again!
-Hoop-

 

[racerone]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

Post pictures of the vacuum operated parts on the carburetors.---Never had the occasion to work on vacuum operated carburetors on these motors.---You may be confused on this operation here.

 

[Hoop1101]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

Thank you, will take more pictures tonight. Yes I absolutely could be confused. It looks like the chokes on the 1990 have vacuum lines running from them, although the actual throttle linkage is still mechanical, but I could be wrong. I also cannot find the fuel pump on the 1990 motor. Is this because it has some VRO pump located somewhere? (I have a factory manual for the 1990 in the mail on its way)

 

[emdsapmgr]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

You will need to swap the intake manifolds to get the correct shift linkage. The 76 lower unit shifts backward from the 90 engine, so you'll need to put the 76 intake on the 90 block. The 150 carbs will only let the block put out 150 hp. Check the throat size of the 90 150 carbs-cast into the face of the carb flanges. May say 1 3/16" or something. Your 76 200 carbs should be 1 1/4"-small for a 200, and not much bigger than the 150 carbs. I'd swap 200 carbs onto the 150 block. They will flow somewhat more air an fuel-making a little more hp. The 150 carbs used a fuel primer system to choke. The 200 used carbs with actual mechanical choke plates to choke the engine. (so they take the old style mechanical choke solenoid. The 90 engine used a VRO oil/fuel pump-mounted on a bracket on the side of the engine. The 76 used dual fuel pumps which dangled by the hoses, on the port side, next to the carbs. The dual fuel pumps each use a pulse line, connected to the block. The 150 block only has one pulse line for the VRO. It should have another port machined at the factory-which the factory put a plug in. You can remove that plug, put a hose barb in it (from the 200 block) to drive pulse line for the second pump for your engine. (the old dual pumps work fine and are much cheaper than the VRO.) The same reeds are used in all V6 crossflows, except the 2.6, which used composite single petal reeds. One thing to consider. The 200,235 and 2.6 used 6 rubber intake filler blocks next to the reeds. Part number 322722. NLA. If you can find 6 used ones, put them into the intake manifold when you are swapping them. They are worth 5-8 hp.

 

[Hoop1101]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

Thank you very much emdsapmgr! Last night I took off the intake manifolds off both motors and swapped the shift lever from the 200 to the 150. Worked perfectly. I looked at the carbs like you suggested, and the 150 carbs have a 1-1/4" throat and the 200's have a 1-5/16" throat. Very close indeed. The VRO pump must have been removed before i got the motor, which was part of what had me confused. I found all the bolt holes and pulse line connections on the 150 block, just like you said. I'll be putting my 2 fuel pumps from the 200 on there. Good suggestion on the intake filler blocks. I'll look for some of those. The reeds look very similar between the two motors except for some slots cut next to the 200's reeds (See pictures). Now I'm just waiting for a new intake manifold gasket to come in the mail, along with a lot of scraping of that old gasket. Whoever put that 150 intake manifold on must have used some kind of gasket adhesive, which I am pretty sure is a no-no from what I've read in the manual. They didn't use rtv or anything like that thankfully.


-Hoop-

 

[175se]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

not vacuum lines those are for your primer.

 

[emdsapmgr]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

The 1 5/16"carbs are the standard size on the early 175 and the (1979) 200 crossflows. Also the GT/XP 150 engines-which put out 165 hp. I'd be inclined to use them. The larger carbs will flow more air/fuel, which means it will make more hp. (The difference between the 150 and 175 is the size of the carbs.) I use gasket sealer on the intake gaskets.

 

[Hoop1101]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

Sounds good, thanks for the info. On the reeds and intake manifold I am going to use, there are a lot of fine metal particles from where a cylinder went bad on that motor. What is the best way to clean the reeds?
-Hoop-

 

[emdsapmgr]

Re: Will a 1979 235HP Johnson Powerhead fit a 1976 200HP Lower?

Aerosol carb cleaner or brake cleaner.