new setup update (85 Johnson 150 crossflow)

[bmurray]

Dhadley and all. Here is where I'm at with my Charger.<br /><br />Boyesen reeds- MUCH smoother idle, and throttle response.<br /><br />CMC jack plate- Think I need to come up more. even though I'm as much as 3" higher than without. see below on prop.<br /><br />Power Tech prop- 14.25x23 UN150HRP. This is an awesome prop. In combination with the CMC I now have tremendous bow lifting and still a good hole shot. The thing I'm fighting is too low RPM's (4900). I must calibrate tach to be for sure. Running tach around my rectifier (bad). My old SST prop was a 14.25x21, but may have been reworked to a 19p cause I see a 19 stamped on the side. Was running low 50's (gps) @5500 rpm's. Boat is deffinately faster, probably close to 60. <br /><br />I will raise the engine up a bit more to see what happens. Try to set 2.5" below pad.<br />I don't want to re-prop. Want to turn this prop in the low-mid 5000's. <br /><br />Now I want a set of used (cheap)heads to modify. I have been told to machine about .125" from it to increase compression. Want to get close to 130lbs and re-jet. I was also informed that the old crosslows were lower compression engines and could use the mod. Any input on this and if so does the 1/8" sound like a good starting point? What model of heads will work better on my engine? Also will 85 235 carbs work on this engine? You can email me if you don't want to tie up the site. Thanks, Bob

 

[bmurray]

Re: new setup update (85 Johnson 150 crossflow)

Dhadley, here is the update you were asking about. I think I just need more POWER.

 

[Dhadley]

Re: new setup update (85 Johnson 150 crossflow)

What youre gonna need is more pistons. <br /><br />Yes the 235 carbs will fit. At only 4900 they probably will not help top RPM more than a couple hundred at best. Acceleration will soffer. Fuel consumption will go up. <br /><br />If you are going to whack up a set of heads you may as well cut the stock heads instead of destroying a set of GT/XP heads. There are so many crossflow V6 heads that its impossible to make a blanket statement like "cut them .125".<br /><br />Personally, I wouldnt do anything to the powerhead until you get the R's up they need to be. At 4900 with a true 23 theoretical speed is about 61. 10% slip puts you just under 55. <br /><br />What is the timing at? I agree with you on raising the plate depending on water pressure. <br /><br />When you get to 6500, then think about the bigger carbs.<br /><br />Don't throw money at it when time will do.

 

[bmurray]

Re: new setup update (85 Johnson 150 crossflow)

I was thinking of machining an old set of crossflow heads. This would allow me to get some more compression. I will be checking the timing this weekend. I do remember my r's dropped a bit when I had a mechanic do some "look overs". He said timing was off a bit and set it. My budget right now doesn't allow me to change the pistons yet. I want to do it with heads as much as possible. I was thinking of boring and polishing the intake, or making some carb spacers. What do you think about copression numbers?

 

[bmurray]

Re: new setup update (85 Johnson 150 crossflow)

Dhadley, what else do you recommend to get the r's up. Would I be better with smaller prop, or do some mods to get the HP up to spin this 23 better? Give me any input.

 

[Dhadley]

Re: new setup update (85 Johnson 150 crossflow)

Youre gonna need new pistons sooner than you think. Carb spacers will slow down a crossflow 2 stroke. You are headed for disaster with this compression thing.<br /><br />Been there. Done that. Including NO2.

 

[bmurray]

Re: new setup update (85 Johnson 150 crossflow)

OK, no carbs, the pistons will be in the off season. Which type, brand, style ect. I do want the compression up, at least what the newer 150 run. What can I do for now? Wouldn't the heads and caps be a good start? Will a smaller prop be better for top speed?

 

[Dhadley]

Re: new setup update (85 Johnson 150 crossflow)

Forget about the newer 150's. They are a completely different motor than yours all together. You cannot compare one to the other. They generate their power much differently.<br /><br />You have not optimized your present set up to establish a baseline. Play with the jackplate height to gage hull response to drag. <br /><br />Watch your water pressure.

 

[bmurray]

Re: new setup update (85 Johnson 150 crossflow)

I plan on playing with the engine height. I did find some heads. An OMC shop suggested the 79 235 cross flow heads. These were of higher compression and could be easily machined. They did tell me that they were the ones most people wanted for hop ups. I could have my choice of any head/cap for $75.00 a pair. I will keep you informed. What about the comment on smaller pitch verses larger? Thanks