Prop Advice
 

I have 1998 38' PQ with stepped hull, 502's with blowers that put out 620 hp on the dyno. I am currently running Bravo props 30" pitch four blade and I am very dissatisfied with the performance. I can run consistently high 70's but I feel the boat should run close to 90 with these motors. Any advice on props or other areas of concern I should look at? The props seem to blow out too soon and cavitate before trimming the boat.

Re: Prop Advice
 

Call Tom at Hydromotive tell him PK with the power quest sent you. Tell him exactly what your specs are, drive ratios, hp and tq numbers at rpms and he will be able to get you a prop that will be best for your current sytem.

330-425-4266
http://www.hydromotive.com/

Re: Prop Advice
 

You might want to post this under the Prop Talk folder too so that Throttle Up or BBlades can help you out. No matter what props you go with, a '98 38 PQ with your motors will not run 90 MPH.

Re: Prop Advice
 

Keep us posted on what you hear from Throttle Up. My guess is they will stear you to a 32 four blade or a 30 five blade. Hydromotive most likley,
Either should get you better speed but no way you will see 90. I have a 2001 38 with the good steps and 575sci's. Top is 84 and I am looking at some prop changes to mabey get me to upper 80'S

Re: Prop Advice
 

Robert,

Does your boat happen to have an all yellow deck and hull with a Mitcher T. paint job? If so, I know the the boat and it's had issues since day one. Not with the boat, but with the power.

Re: Prop Advice
 

Props and Superchillers could get your boat to 90 MPH. Have you given any consideration to adding intercoolers?

Re: Prop Advice
 

Hay Knott

Up here in the north country a Supperchiller is an intercooler.
See below

Re: Prop Advice
 

I know that, which is why I asked if you had given any consideration to adding them. Your engine pics in post #4 don't show any intercoolers on the motors. That is why I said props and Superchillers could get you to 90 MPH. It would appear that you have already added the Superchillers. But thanks for trying to make me look like a dumba$$.

Re: Prop Advice
 

Just spreading a bit of the Christmas cheer while I yanked your chain.
Relative to the Super Chillers on my 575's they really didn't add that much to the top end. Best wiith them was about 88, around a 4 MPH gain .

Re: Prop Advice
 

I ran a set of 29 5 blades last summer and they did the best for me. Throttle up help me alot on this.

Rich.

Re: Prop Advice
 

Thanks everyone for your feedback. I have been reading them but haven't had the chance to respond until now. I am not planning on seeing 90 (would be nice but not realistic I know) but I am not happy with the performance that I am seeing in the upper 70's either. I have had both engines freshened up and they are running strong with dyno numbers of 620 hp plus. This kind of power should push into mid 80's but I am not seeing it. Thanks again for your comments and I am looking forward to any more thoughts any of you might have. I would also like Silverado to clarify what he knows of the history of the boat.

Re: Prop Advice
 

Did you talk to throttle up ?

Re: Prop Advice
 

Dyno 620 HP at the crankshaft, but you are probably only getting 530-540 HP at the prop. Everybody looks at HP, but you need to have the torque also. A Mercury 575sci is rated at 550 HP, and those engines run low 80's in boats with the "new" bottom. The original owner had concerns about speed also, so the factory pulled his blown 502's and put brand new 502's in to prove to him that there were no issues with the boat or hull bottom. I beleive the boat ran 71-72 MPH with stock 502's, just like many of them did. You have an "old" bottom that's had the strakes cut and sharpened (this has been discussed in other threads). Your 502's came out of a 290 Enticer that the orignal owner had before ordering your 380. I'm not saying this negatively, but I don't think you are you going to see anymore speed out of your boat than what you've got.