Johnson crossflow horsepower question

[jy118lfd]

I know this has been brought up before but I want to hash this out once and for all. Johnson crossflows V6 in 150 175 200 and 235. What is the difference in the ratings? I know that they went to the 2.6 for the 235 in 83 and that the exhaust is much larger on a 235 than the rest but as far as I can see the 150 175 and 200 are only different in the carbs. Is this why everyone thinks you can change carbs on a 150 and get 200hp Is this true on these motors? and if so what combos have you tried and how have they worked? I have a set of 235 175 and 150 carbs but if I can put 200 carbs on a 150 and get 200 I will buy them. Thanks to all that reply and I cant wait for the discussion that this provokes

 

[Dhadley]

Re: Johnson crossflow horsepower question

The 150 and 175 crossflow powerheads are identical. The 200 has slightly different porting. The 235 was 3.500" std bore in 1978 and 79. In 1980 they went to a 3.625" std bore (2.6 L).<br /><br />The 235 block (exhaust) is different than the "flat back" 150/175/200.<br /><br />Some XP/GT 150's have 200 porting. The 150 XP/GT's have different heads than the rest. The 2.6XP/GT has really big carbs.<br /><br />The smaller the carb throat, the quicker the motor accelerates. The bigger the throat, the more top end -- theoritically.<br /><br />They all have the same stroke and gear ratio. The bore is only different on the 2.6 blocks (1980 and up 235's and 2.6 XP/GT)<br /><br />It takes a pretty good hull design to see the difference between a 150 and a 200 with the same set up. I have a 20' Dusky which is a very ordinary design -- no pad or step -- and we have run every crossflow you can imagine (stock configuration) on it at some point. And a bunch of loopers. We really dont see any major difference, in the crossflow line, from one to the next.

 

[BrianTindall]

Re: Johnson crossflow horsepower question

Wow, all summer has passed and this is the first time I've had to even look at this forum! How about another question from NJ? I have a 1984 2.6L Seadrive (ducted version) with 400 original hours on it. The drive bracket is missing several parts so mounting as is won't work. I have two J175's coming (1 is a 1985 with a bad cylinder, the other is a similar year). Will the 2.6l block bolt up to the 175 exhaust housing? I'd like to make a good runner out of it. The 1985 with the bad cylinder has a fresh lower unit on it, that's the reason for swapping the blocks. My family and I were watching very intently during the storms. My parents live in North Fort Myers. I hope you made out ok.

 

[Dhadley]

Re: Johnson crossflow horsepower question

The 2.6 and the 2.5 are not a direct bolt on swap. The 2.6 with the "bubble back" exhaust sits on a different adaptor plate. You can change the adaptor, and related parts, from one mid section to the other. If its a saltwater motor it may be a bit time consuming.

 

[jy118lfd]

Re: Johnson crossflow horsepower question

I performed a similiar swap this summer. I swapped a 235 bubbleback powerhead for a 150 powerhead. The 150 is a flat back motor. I changed the whole midsection so I would not have to take out the bolts for the adapter plate. The swap was a simple remove and replace procedure except for the midsection I got had a powet tilt and trim unit on it. The two upper bolts and two of the lower mount bolts were frozen. A little heat and gentle persuasion an it came off . Not too hard and it worked great. Good luck with your swap

 

[ledgefinder]

Re: Johnson crossflow horsepower question

DHadley, is the 150 noticeably more fuel-efficient than the 200 & 175?

 

[Dhadley]

Re: Johnson crossflow horsepower question

On identical set ups -- both properly set up -- I've not seen much difference. Some but not a lot.<br /><br />The loopers are better on fuel especially the 60 degree 150/175.

 

[BrianTindall]

Re: Johnson crossflow horsepower question

Jon, actually I was thinking about doing just that. The idea was to find a blown engine to rob all the shift/throttle linkages, lower engine cowl, engine cowl itself and the transom brackets with the trim and tilt assembly. But with two motors coming, I was exploring the idea of just swapping the powerheads. If I may ask, where in Jersey are you located? Now, maybe someone can chime in a let me know how hard it "Normally" is to remove the two upper pivot arm bolts (the two stainless ones that go in just under the powerhead). By using the blown engine for parts, it would save having to go through swapping the exhaust adapter plate and other things.

 

[jy118lfd]

Re: Johnson crossflow horsepower question

Brian I am in Bricktown, Ocean County. The upper pivot arm bolts if I understand are the upper mount bolts for the midsection. I had to torch off the heads of the donor midsection but on my motor I just heated the area where the shank goes through. They came out fairly easy. In what i've seen the bolts that get stuck always are stuck in the shank area not the threads. The heat seems to free the salt crud that sticks them. One other thing I have also heated bolts and used flux for soldering to free them, the flux is attracted to the heat and also lubricates the parts. It works better than the best wd 40 and pb blaster could do

 

[BrianTindall]

Re: Johnson crossflow horsepower question

Thanks for the info. I also have a 1988 3.0l Seadrive to convert over to a standard style OB as well. This will eventually replace the engine on the boat now. That one will then become a spare. I was just up your way last Thursday. My mother-in-law lives in Brick, just off of Old Hooper Ave.

 

[jy118lfd]

Re: Johnson crossflow horsepower question

Thats real close I am on Lake Shore in Lake Riveria just off Brick blvd

 

[BrianTindall]

Re: Johnson crossflow horsepower question

Amazing that on such a large forum how people pop up almost right next door! I have one of the J175's coming Wednesday. Going to pull it off the boat at work with the fork lift. Being the supervisor has it's perks! Actually, I'd let any of the guys I work with have the ok to do this, they bust their butts too! The plan is to put together running motors to sell and part out the rest. Kind of like I do with model airplanes. Helps feed the habbit, I mean hobby!