Need Engine Help Quick!!
#1
Registered
Thread Starter
Join Date: Oct 2000
Location: Kansas City, Missouri, USA
Posts: 305
Likes: 0
Received 0 Likes
on
0 Posts
![Unhappy](/forums/images/icons/icon9.gif)
Ok everyone, I need some help here. As many of you know, I have been redoing my engines over the winter. What I did was take my stock 525SC’s and replaced the blowers, carbs, pulleys, belts, etc. Prior to this I was running 88-90 with standard Bravo’s on my single step 35’ Fountain. After the new 420 mega-blowers, new carbs, belts, pulleys and nose cones on the drives were added, I’ve lost 3-5 mph. Obviously we thought it was the drives or props so we tried a 26, 28 (original), 30, and 32 pitch prop with little to no difference in any of them. We then tried 2” shorter drives because we could not get the props to blow-out getting on plane like they had been, still no change and still lower speeds. We got anywhere from 5400-6000rpm’s with then props, but nothing helped. Finally, we thought maybe the engines had a compression issue or leak, but we tested them both and they were perfect. The only thing we can think of is that we aren’t getting the horsepower we should. If so, how’s that possible? What could possibly be mismatched that would be causing this problem? Should I spend the money to have them dynoed, then find out it isn't producing the horsepower, but not know where the problem is or find out they are producing more with lower speeds? Everyone working on this is completely frustrated!! Help!!!!!!!
#4
Registered
Thread Starter
Join Date: Oct 2000
Location: Kansas City, Missouri, USA
Posts: 305
Likes: 0
Received 0 Likes
on
0 Posts
![Default](/forums/images/icons/icon1.gif)
Matt still has the boat and he's been more than helpful. That group over there is amazing. We are looking at the MSD box now because it has some technology in it that allows it to retard the timing depnding on the boost. We thought we had bypassed it by locking the timing at 34, but we may not have been totally successful. Does anyone have experience with this type of MSD boxes?
#5
Ginger or Mary Ann?
![](https://www.offshoreonly.com/forums/images/icons/charter_member_star.gif)
![Default](/forums/images/icons/icon1.gif)
Seems that if you can still turn the motors at 5400-6000rpm with your original props, the motors have to be ok. That just leaves the nose cones as the other possibilty. Can you try another set of unmodified drives?
__________________
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
#6
Registered
Join Date: Mar 2004
Posts: 31
Likes: 0
Received 0 Likes
on
0 Posts
![Default](/forums/images/icons/icon1.gif)
What is the horsepower supose to be?? Give me RPM and what prop u are using. How high is your trim. Are tabs up or down? What year is boat?? I've built many Fountains and know what works and what dosn't. How much more boost are you running. have carbs been changed or modified. You should run 34 total timing with good 92 Fuel and be Ok. That motor came with 256 Wieand blower with 1 carb. Do you have 2 carbs on 420 blower?? If not u will need 2 carbs.. Let me know... Did u change the cam?? give me the specs and I may be able to help or fax them to me 925-516-7682 Steve
Last edited by OffDuty; 05-06-2004 at 12:24 AM.