Lost 4-5 mph

[Uinthas]

This spring I was able to run 38-39mph. I then had an electrical problem & have spent quite a bit of time in repairing that (turned out to be the trigger) last time I had my boat on the water I hit ground & tore a 1" gash in my prop, I bent it back some but not completely and had a little nick tear out of it.. I also of course had to re-set the timing & have it at 10degree's BTDC (going to double check this sunday) I dont know what the timing was set at before, I just used what the manual suggested. The motor runs GREAT & fires right when you hit the switch. At this point I dont know if it's the timing or the prop that has made me loose that power, any suggestions?? Unfortunetly I dont have a tach to tell you what RPM I'm running. My motor is 87 85hp on a 17' Bayliner capri.

 

[CoachHolland]

Re: Lost 4-5 mph

You were getting nearly 40 MPH out of your Bayliner with that motor? Wow, that's nice. What size prop were you using?<br /><br />A bent prop with some structural damage can defintely cause you to lose MPH, but you should also notice some vibration that wasn't there before if that is the sole culprit.<br /><br />Since you don't have a tach, does the motor *sound* like it is revving at the same speed that it was before? You can make a guestimate on that.<br /><br />However, my manual states that your timing should be 32 BTDC static and 30 BTDC dynamic. If you're at 10 degrees, you're way off.

 

[Uinthas]

Re: Lost 4-5 mph

coachholland, you may be correct, there is the mark for the advance 30btd I think is what it was, I could be wrong I'll check again.. what is the difference between static and dynamic timing?? I timed it as the manual suggested, just cranking on the motor without it running?? let me know, thanks..

 

[CoachHolland]

Re: Lost 4-5 mph

From what I understand, yes it is just turning the engine over. Your motor running should give you 30 degrees.<br /><br />What size prop are you using to get that kind of speed?

 

[Uinthas]

Re: Lost 4-5 mph

Sorry, forgot to answer the prop question.. I just went out & took the prop off & looked over it up & down & was not able to find any #'s on it. If memory serves me correct it's a 19. Where would the # be listed, I looked all over.. the 38-39 mph is with just me in it (190lbs) & this is the reading off my fish finder. I took my GPS out one time & was actually 3-4 mph slower then what the finder read. <br /><br />Aslo yes my motor sounds to be running the same RPM but this is only a guess.. I dont feel any extra or noticable vibration from the motor either..