Go Back  Offshoreonly.com > Owners Forum > Baja
Prop question / engine issue (long story sorry) >

Prop question / engine issue (long story sorry)

Notices

Prop question / engine issue (long story sorry)

Old 06-05-2013, 11:46 PM
  #1  
Registered
Thread Starter
 
Join Date: Aug 2011
Location: Dunkirk ny
Posts: 440
Likes: 0
Received 0 Likes on 0 Posts
Default Prop question / engine issue (long story sorry)

I just got my boat back ready for the season. The mechanic and I discover good news. I don't need a new prop. But I called the prop company and they said I still need a new one becasue the oppsite has happened.

Long story made longer: Last year I blew my engine ( 502 m1 procharged engine in my 1997 24 ft outlaw )and had it rebuilt and had all the corrections made by my mechanic, (fixed the original owners mistakes). But problem when we first took it out was that even though the rpm gauge was showing 5000 to 5200 and the msd box had a 6000 rpm chip in it, my mechanic assume that the rmp gauge was off because it was sputtering alittle at 75 mph. So he thought the msd box was kicking in even though the rpm gauge was not reading 6000 rpm. So with that thought, we decide ( since it had a bigger cam in it ) to go smaller cam or higher pitched prop for next season. Prop idea is cheaper then the cam change so i called a prop place and told them I need to get a prop higher pitch to lower my rpms. I Was already to go and get a new prop and we discovered something new. Two weeks ago at the marina I had the mechanic change my fuel pressure regulator becasue it seemed that the fuel pressure was on the low side for my m1 procharger. We changed it out to a areometer one. Pressure was still low. As a result we discovered the way the fuel pump was set up was that we were still running off the original mechanical fuel pump and the add on electrical one was not doing much. And the original add on holley electrical pump could not handel the job even if put on the system correctly. So we put a areomatic 700 to 750 one on the boat. After that everything seemed to run perfect. Rpms never went over 5000 or so and we hit 75 mph (my speed gauge is accurate to my gps on phone). So our assumption was that the false sense of the msd box kicking in last year at a 6000 rpm was not at all the msd box and a false rpm reading but ( becasue of my mechanic's findings in the begining of this season was that the fuel pump was starving the engine alittle bit and spudering the engine becasue the slit lack of fuel pressure at top speed. With the trim tabs down all the way , or the trim on the out drive all the way up we could not get it to go mover 5200rpms and trip the msd box at all, The box is set for 6000 Rpm . Good news right. I was excited
mechanic said the engine was desinged for max and safe running at 5200 rpm ( friends told me the bigger the engine the lower the rpms should be for safty of the engine and longevitiy

I told the prop guy this and he now said the complete opposite, "that now my engine is running under rpms and i need a lower pitched prop 2 or 3 pitches instead of a higher pitched prop, becasue NOt sure if i am saying this right but Under running the engine with to low of rpms (loading the engine) will cause more heat to the engine , out drive ect and it will also decrease my power and torque and will do more damage to my engine and I should be running 5600 to 5800 becasue it is a 502 and has a m1 procharger. i thought lower rpms is safer for any engine to have it last longer and not damage the engine. He said that the procharger will make it run alot more higher rpms then i am running. This prop guy has confused my new found excitement for not spending more money. I am confused. Please help with insight. Sorry for the long duration of info. don't know how to explain it in a short version due to my lack of experience here in the field. I thought slightly lower rpms is better then higher ones from what i learend
ps: (it is a labbed 4 blade spinelle prop unknown pitch) no markings

Please help
please tell me he is trying to sell me something i don't need right now. All i want is to enjoy it and take my son tubbing off it.
and wake board off it
please help
conneroutlaw is offline  
Old 06-06-2013, 07:50 AM
  #2  
Registered
iTrader: (2)
 
Join Date: Jun 2010
Location: Birmingham, AL
Posts: 392
Received 0 Likes on 0 Posts
Default

Unless you are trying for absolute top speed 5000 rpm should be a safe number for that engine. I wouldn't change a thing. I certainly would not turn it to 5600 or 5800 without knowing exactly how the engine was built. You would be doing yourself a disservice proping it for that rpm anyway if your primary interest is watersports or cruising.

Good luck,

Dan
BajaDan is offline  
Old 06-06-2013, 08:10 AM
  #3  
Registered
Thread Starter
 
Join Date: Aug 2011
Location: Dunkirk ny
Posts: 440
Likes: 0
Received 0 Likes on 0 Posts
Default

Dan,

thanks for the information, I thought the same way. At first we thought we were running to high until my new findings. I was glad about our new findings, and my mechanic said that engine was built to run 5000 to 5200 rpms, The prop guy said the engine should run higher rpms becasue of the prop charger and it will casue more damage to the engine becasue rpms to low will run the engine hotter and out drive hotter. The low rpms and higher heat didn't make sense. i would think lower rpms is better for the engine and lower heat. i have enough power , the boat does 76 on the gps and it starts to become a little unstable. I have full hydraulic steering too. It helps alot. i think i will stay with what i have. I think he was trying to make me parenoid to buy a
1000$ and he won't care if the engine blows and if it does , he will blame the engine and not the prop

thanks for the info

jj
conneroutlaw is offline  
Old 06-06-2013, 08:54 AM
  #4  
Registered
iTrader: (2)
 
Join Date: Jun 2010
Location: Birmingham, AL
Posts: 392
Received 0 Likes on 0 Posts
Default

Well too low an rpm at too high a load (called lugging) will certainly damage an engine. I don't think 5000 rpm is too low a full throttle rpm however. How much boost are you running on the procharger? I am sure that some of the guys that are running this setup will chime in here soon.

Dan
BajaDan is offline  
Old 06-06-2013, 12:59 PM
  #5  
Registered
Thread Starter
 
Join Date: Aug 2011
Location: Dunkirk ny
Posts: 440
Likes: 0
Received 0 Likes on 0 Posts
Default

I am running 8 pds of boost

jj
conneroutlaw is offline  
Old 06-07-2013, 01:56 AM
  #6  
Registered
 
Join Date: Oct 2009
Location: central IL
Posts: 1,125
Received 153 Likes on 69 Posts
Default

First, this isn't a Baja specific issue so you'd get more responses if you'd posted in the prop or engine section.

Second, the procharger won't make your engine able to spin more rpm. It will make the engine be able to turn a higher numerical prop at the same ideal rpm with the added horsepower. Just because the MSD box has a 6k chip in it, does NOT mean the engine is ok to spin that hard. The engine needs to be dyno'd to find out where peak horsepower is so you know what RPMs you should be running flat out.

Honestly, from your past posts/problems you seem to have bought a boat that is above your "know how". Not to be mean but when you bought that boat and started asking beginner questions, I had a bad feeling the motor would be toast sooner than later. My advice is to pull the procharger off and put a prop it accordingly (one that you know what pitch it is also).
Plowtownmissile is offline  
Old 06-07-2013, 08:30 AM
  #7  
Registered
iTrader: (2)
 
Join Date: Jun 2010
Location: Birmingham, AL
Posts: 392
Received 0 Likes on 0 Posts
Default

Originally Posted by conneroutlaw
I am running 8 pds of boost

jj
Thats a lot of boost unless the engine was specifically built for it (lower compression etc). Remember that you can overload an engine at any rpm. It is a complex issue related to fuel octane, compression ratio (and boost), temperature, combustion chamber shape etc but it manifests itself as detonation which is an explosive combustion of the fuel/air mixture rather than the normal burning of that mixture. High speed detonation (5000 rpm certainly qualifies) will ruin an engine in seconds and you will likely never know it happens until you tear the engine apart to see whats wrong. Your prop guy is right to a certain extent in that making the same power at a higher rpm in a more lightly loaded condition will reduce the chance of detonation but it could just as easily cause other problems that are just as devestating.

If you don't know much about the engine build, and you believe it to be stock, then you can certainly do as plowtownmissile suggests and remove the procharger. You could also change pulleys to reduce the boost down to 2-3 psi for a nice performance gain over stock and hopefully a reliability improvement (it is, after all, running with no apperant problems now). It just comes down to how much risk you want to take and how much that 75 mph top end means to you.

Good luck,

Dan
BajaDan is offline  
Old 06-07-2013, 09:37 AM
  #8  
Registered
Thread Starter
 
Join Date: Aug 2011
Location: Dunkirk ny
Posts: 440
Likes: 0
Received 0 Likes on 0 Posts
Default

cancel it

Last edited by conneroutlaw; 06-07-2013 at 09:55 AM.
conneroutlaw is offline  
Old 06-07-2013, 09:46 AM
  #9  
Registered
Thread Starter
 
Join Date: Aug 2011
Location: Dunkirk ny
Posts: 440
Likes: 0
Received 0 Likes on 0 Posts
Default

cancelled post

Last edited by conneroutlaw; 06-07-2013 at 09:55 AM.
conneroutlaw is offline  
Old 06-07-2013, 09:51 AM
  #10  
Registered
Thread Starter
 
Join Date: Aug 2011
Location: Dunkirk ny
Posts: 440
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Plowtownmissile
First, this isn't a Baja specific issue so you'd get more responses if you'd posted in the prop or engine section.

Second, the procharger won't make your engine able to spin more rpm. It will make the engine be able to turn a higher numerical prop at the same ideal rpm with the added horsepower. Just because the MSD box has a 6k chip in it, does NOT mean the engine is ok to spin that hard. The engine needs to be dyno'd to find out where peak horsepower is so you know what RPMs you should be running flat out.

Honestly, from your past posts/problems you seem to have bought a boat that is above your "know how". Not to be mean but when you bought that boat and started asking beginner questions, I had a bad feeling the motor would be toast sooner than later. My advice is to pull the procharger off and put a prop it accordingly (one that you know what pitch it is also).
I agree with you. I didn't have much knowledge for this new hobbie. I boated all my life but not at this level. before this i had a 19 ft baja with a 3 liter engine (top speed was 38 mph). I did get in over my head. I am learning fast and found a great mechaic. Originally the reason i blew a head gasket was that i didn't have arp studs to hold the engine together and my mechanic found a few other things down not correctly. I talke to my mechanic today and and he told me my engine should be running at max 5200 rpms. I know i don't want to run it at 6000 rpms and he said the same. Last year we made a false assumption about the rpms and that is when i called the prop manufacture. After we resolved the issude wirth the new fuel pump, Our new understanding was it was sputtering becasue of lack of fuel not msd box. Meaning last year the engine spudddered at 75 mph and the rpms were only 5200 , so we thought the rpms were off and the msd box was kicking in, we thought the gauge was lieing to us. But after we changed the fuel pume to areomotive fuel pump we ran it at 75 pgs speed and no problems and the max rpm was 5200. So we corrected the problem.

i told the prop guy this and then he gave me a spin around telling me we need to lower the pitch on the prop to raise it to 5600 to 5800 rpms, and we should be running it at a higher rpm becasue of the super charger. But like you stated earlier and what my mechanic told me, i agree with the super charger and rpms. I think the prop guy was worring on losing a sale and gave me bull**** to help save the deal of me buying a 1000$ on fri from him. Thank you for your insight and since 2 poeple agreed on the same topic, i found my real truth and neither of you are selling me a prop. So i trust you both

thank you
conneroutlaw is offline  

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.