Jets or Prop

With another season fast approaching I'm anxious to get the boat out that I got last Fall. I'm still dealing with a problem with acceleration. My '78 175 BlackMax roars once you get it going. I've gone through the carbs and changed just about everything, but I think I may need to rejet or change props. I'm running the jets in the manual for 5000-7000 ft. It runs excellent if I can get it to open up. When I acclerate it cuts out and dies unless I hit the choke. <br /> Sorry for the long post, but I need help knowing a lot of things. My fuel tank may be partially to blame. I was wondering what diameter the pickup line should be in the tank. Right now it's really large. May the fuel pump can't pull that much fuel volume from the tank.<br /> Please help if you have any suggestions about jetting, props, or the fuel line sizes.<br /><br />Thanks!

Re: Jets or Prop

Drew, That is usually a symptom of the idle mixture being set too lean. Try to richen each carb 1/8 turn, and test it. Start with the top carb. You need to trade a nice smooth idle (too lean to accelerate) for a rough idle (rich enough to accelerate).

Re: Jets or Prop

Fuel lines should be 3/8"ID. Rebuild fuel pumps if setting carb doesn't work.

Re: Jets or Prop

Chris I beleive he has fixed jets.

Re: Jets or Prop

I've finally had the boat out this season, what a time! I'm still having the same problems as before mentioned on my other posts. I'm pretty happy with the boat, but it needs some extra help. I'm running a 19P prop on a 19.5 foot Crestilner 990 cuddy cabin. The engines purrs but won't let you punch it. I have to ease into it or choke it and then punch it to get it to work. I've tried rebuilding carbs, fuel pumps, new bulbs, new lines, tank pickup hose, etc. Nothing seems to work. The jets are set for 5-7000 feet where I live, but I'm wondering if changing to a 17P or 18P prop would fix my problem? My RPM as of Saturday was 4800 WOT, water was pretty choppy and there was a head wind. Speed was about 38 mph. I read that 1 pitch change equals 500RPM. Is that reasonable? If so, I'll be pushing max RPM with an 18P, but it doesn't seem that that will make that much difference. Any help from you experts would be much appreciated!

Re: Jets or Prop

You definitely need to get the RPM's up. 1 inch pitch equals 200 RPMs, give or take a little. A 17" prop would help out alot on acceleration and cure the sluggish response your getting. But that will still put you shy of maximum RPM range by quite a bit.. Nor will it help the cutting out and dying problem, which I believe is low speed carb related...

Re: Jets or Prop

Try a linc and synk. Double check the timing and adjust the carb's. Tim