rpm range

[Texan_Ron]

my father has a 1968 17' glastron tri-hull with a 1974 johnson 135hp outboard and with a alum 19" prop the engine will not run over 3800 rpm's at 35 mph does this sound right I read in many topic's on here where the engines runs well over 4000+ rpm <br />tks<br />Ron

 

[ezeke]

Re: rpm range

The factory prop was 13" diameter with a 19 pitch. The gear ratio was 13:25. The full power range was 4500 to 5500 rpm. The 135 HP rating was achieved at 5000 RPM. If you want to get more power, lower the pitch of the prop.

 

[Dhadley]

Re: rpm range

Is this rig new to him or has he had it awhile? Has it always done this or just started?<br /><br />Lets start with the basics. If pitch is the only issue at work we'd have to lose 8 to 10 inches of pitch to get near the 5800 rpm mark we're looking for. Start with a compression check. Then check spark. If these check out OK, look at the carbs. Perhaps a good cleaning and rebuilding is in order if you havent done so in a while or if its been sitting (has it?). Some new Champion (Q)L77JC4's would be nice too.<br /><br />Then if all this looks good, follow the sync-n-link proceedure in the service manual to make sure the linkages are correct. Make sure you are getting full spark advance.<br /><br />Dont overlook the possibility of trapped water in the hull.<br /><br />Good luck!