1989 trophy 2459 5.8l recommended prop size and pitch-gctid820867

[man4fire]

I just rebuilt 5.8l omc.030 over and upped the cam a little otherwise stock 24' hardtop with cobra drive. I have a 15x16 on the boat it came with but thinking not the best. any recommendations . First post. Thanks

[Guest]

My 5.7 gm (new base engine)is mated to a 5.0 geared cobra on an 89 2160. I currently run a three blade aluminum 15x17. It will redline over engine spec. if I let it. It needs a 19p at least to hook up the 5.7 properly. I'd start there at 15x19 three blade or 15x20p four blade.

[CptCrunchie]

I run a 15x17 on mine. WOT is 4600 RPM @ 35kts.

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[dktool]

"man4fire" post=820867 wrote:
I just rebuilt 5.8l omc.030 over and upped the cam a little otherwise stock 24' hardtop with cobra drive. I have a 15x16 on the boat it came with but thinking not the best. any recommendations . First post. Thanks

I run a 15 1/2 x 15, have tried others but this is the sweet spot. Your 15x16 is virtually apples to apples to mine so as long as it doesn't need to be serviced, you should be good.

That 5.8 has a sweet torque power band doesn't it ?

[man4fire]

yes it pulls forever and hole shots well and it is fresh .030 over rebuild with a bit more cam. Never had too much time at WOT but would like to troll slower and cruise faster. Prop math eludes me. i know I have to get out this week and WOT a couple runs and come back to you all. Thanks. Not worried about the motor it will perform. I was thinking about a 19 but it may be to much pitch.

[dktool]

"man4fire" post=821018 wrote:
yes it pulls forever and hole shots well and it is fresh .030 over rebuild with a bit more cam. Never had too much time at WOT but would like to troll slower and cruise faster. Prop math eludes me. i know I have to get out this week and WOT a couple runs and come back to you all. Thanks. Not worried about the motor it will perform. I was thinking about a 19 but it may be to much pitch.

Yes, you will find a 19" to be way to tall for your load, I could(did) live with a 14-1/2 x 17 SS which I ran for awhile but the larger dia. and less pitch of the 15 1/2 x 15 gives more lift and less strain on the drive train.

I never need to "hammer it" to climb out, it will get on step with just nudging the throttle forward. I don't think I ever run much over 50% throttle, the conditions I run in don't allow for anything over 25 mph.

The last time I recall a WOT pull on flat water trimmed very loose, it was on it's way to 40 mph when pulled out. That was with the 17" SS

Did you by chance change your heads to GT40's ? Center riser manifolds ?

[man4fire]

The heads are the same had to go to center risers which caused a complete redesign and relocation of heat exchanger to above water pump. What a pain. Also shifted my 2 agm 110# batteries to just inside the cuddy centered to shift 220lbs weight forward and balanced the weight better. Taking it out tomorrow to see how it rides and hope it doesn't bounce so much.