Anti cavitation height?

**Jsynhon** · 06-10-2018, 09:44 PM

Got a 1980 model Mercury V225 on a 19ft 1993 Hydra Sport LS180. Having holeshot issues. Once it planes it runs fine. Had a Mercury Fury 24p that pushed it 62 mph but hell getting out the hole. Just put an aluminum 23p Mercury prop on it. Better but still crappy performance out of the hole. 53 mph on 23p. From pad is 2.75 inches to bottom of cavitation plate and 5.5 from center of prop spline to pad. Is this even close to right? 80psi each cylinder cold. 90psi hot.

**Merc 2.5** · 06-12-2018, 11:57 AM

IMHO those #s mite b ur whole prob, but ur height of motor is pretty close to where it needs to be , perform a leak down test if possible, what is ur wot rpm?

**faztbullet** · 06-13-2018, 06:34 AM

She's tired....

**Jsynhon** · 06-13-2018, 01:22 PM

Originally Posted by Merclover

IMHO those #s mite b ur whole prob, but ur height of motor is pretty close to where it needs to be , perform a leak down test if possible, what is ur wot rpm?

Tach shows 6100 on 23p. About 5800 on 24p. Will try and rig a leakdown device. May just be powerhead or upgrade time. It runs great once it is out of the hole.

**Jsynhon** · 06-13-2018, 01:23 PM

I'm afraid you are correct!

**Merc 2.5** · 06-13-2018, 06:39 PM

Seems to me that motor should run those rpms with a 25 or 26 prop,, id say needs rings,if you was to tear it down now could possibly just do rings and bearings tho,if you keep running it could possibly do more damage to sumthin

**Jsynhon** · 06-14-2018, 01:50 PM

Originally Posted by Merclover

Seems to me that motor should run those rpms with a 25 or 26 prop,, id say needs rings,if you was to tear it down now could possibly just do rings and bearings tho,if you keep running it could possibly do more damage to sumthin

Should be a chrome bore. How do I know? I've built V8 engines in the past. Can't be too terribly hard to rebuild the rotating assembly.

**hsbob** · 06-21-2018, 12:07 PM

try na set of doel fins. at $40 it a quick solution for hole shots. i've had a set on all my motors since 85. if you look at the older race boat they all has fins on the cavation plates.

**Glasstream15** · 06-21-2018, 03:59 PM

It looks to me like you're at least 2 inches too deep. And, if compression gauge is right it's getting tired.

**Motv18** · 06-21-2018, 08:26 PM

Looks tired.

But hows your trim angle when you take off. To far out and you push down and torque the bow up. To much in and about the same look but it tries to lift the stern and bow will come as well. Neither will give a good whole shot.

Odd question but what’s the stall speed as you come out of the hole. If it hangs 3500-4000 things are probably good just tired. If it hangs 2500-3000 you would have a look for something half broke or to much pitch. 3000-3500 is decent and just depends on how long it hangs.

Some old old stuff even when new just didn’t get up on plane well. Old bass boats loaded would take 7+ seconds till the bow would start coming down. Vented props helped a lot when they came around.

**ChrisCarsonMarine** · 06-23-2018, 06:22 PM

That motor was not very powerful on the bottom end from the beginning, should have around 125 pounds of compression, if it’s 80 to 90 it’s not tired, it’s asleep, Chris

**tlwjkw** · 06-24-2018, 12:06 PM

'bout 3.5 inches pad ta center prop shaft (startin' point) but if ya have faith in that gauge movin' tha motor, like indicated, won't do much good...………….