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BeefSupreme

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403 olds is just slow?
« on: July 24, 2021, 04:57:09 pm »
Hey everyone. I recently picked up this 83 charger bubble deck with a 403 olds and berkeley 12JE pump. I rebuilt the carb, replaced the fuel pump, and took it to Silverwood Lake to test it out. The boat overall ran pretty good but it would only get to 4000 RPMs and my gps speedo clocked it 42 MPH top speed. is that normal? I feel like I should be getting more RPMs and the guy I got it from said it would do somewhere around 60 MPH so I'm a little disappointed to see 40. Should I expect more out of this setup? If so how do I get it? Any help is appreciated

just a little more info: the carb is a holley 600cfm double pumper on a edlebrock performer intake. hardin marine thru the transom exhaust. And the engine has some 3A heads I think are from a 350 olds
  • Boat #1: 83 Charger
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mash on it

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Re: 403 olds is just slow?
« Reply #1 on: July 24, 2021, 10:24:37 pm »
A quick Google search showed the 403 olds made a whopping 185 hp. But that's net hp. If the gross hp was 100 hp more, you're working with 285 hp.

Per Jet Boat Performance impeller dyno, and assuming an "A" impeller, it's producing 228 hp. At least it's above net hp levels.

I ran a mild 350 Chevy, to 45-4600 rpm, "A" impeller. Chart shows 326 hp, and summit and jegs list it as a 330 hp engine. (Very similar combo).

Also at Silverwood, you're probably down 2-300 rpm due to elevation.

Couple of things to check-
Accurate tach?
Pump condition?
Proper timing?
Tired engine?
Pitot speedo or gps? (Pitot speedos are notoriously inaccurate)

I can't see 285 hp (or 228 @ the impeller) breaking 50. 40 does seem low.

Just my $0.02

Dan'l
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BeefSupreme

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Re: 403 olds is just slow?
« Reply #2 on: July 25, 2021, 11:03:02 am »
I appreciate your $0.02! But I just made a pretty big discovery. I was checking the casting numbers on the block and it’s actually a 350 olds. That explains the heads. I have a suburban with 454 at my dads maybe I’ll look into swapping that into the boat later down the road because I wanna go fast haha
  • Boat #1: 83 Charger
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mash on it

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Re: 403 olds is just slow?
« Reply #3 on: July 25, 2021, 11:40:06 am »
That makes more sense.
Run of the mill olds 350s were rated at 160 to 185 hp, net.
So turning 4K at Silverwood lake at 3500' elevation (228 hp absorbed, theoretically) is pretty respectful, considering. Assuming an "A" impeller.

A mild cammed 454 and headers can easily hit 400 hp. 500 isn't that difficult either.

The draw back is the e pump, not the greatest for performance potential. The shape of the intake/hull hinders water delivery to the impeller. But for a mild hot rod, it'll be fine and fun.

Dan'l
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96Laveycraft21Xt

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Re: 403 olds is just slow?
« Reply #4 on: October 14, 2021, 04:34:33 pm »
I appreciate your $0.02! But I just made a pretty big discovery. I was checking the casting numbers on the block and it’s actually a 350 olds. That explains the heads. I have a suburban with 454 at my dads maybe I’ll look into swapping that into the boat later down the road because I wanna go fast haha

Hey there!  Dont count the olds out yet! haha.  brother in law has an 88 commander with a 350 that i think is only rated for 265 hp and it turns i think he said 4300 or 4400 with a berkeley A impeller at the colorado river (lower elevation but hot crappy air)

You shouldnt have too much trouble getting the olds up to 55 mph if you were so inclined before attempting a BBC swap.
  • Boat #1: '96 Laveycraft 21' XT Ski
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BeefSupreme

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Re: 403 olds is just slow?
« Reply #5 on: November 17, 2021, 09:41:48 pm »
I typically only run the river too. I just go to silverwood for annual pre season shakedown. Since I have some other projects going already, I’m just going to pull the 350 this winter and clean it up and go through some things and drop it back in. I wouldn’t mind doing a few budget friendly upgrades while I have it out. If you have any suggestions I’m all ears.
  • Boat #1: 83 Charger
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96Laveycraft21Xt

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Re: 403 olds is just slow?
« Reply #6 on: December 16, 2021, 01:38:51 pm »
I typically only run the river too. I just go to silverwood for annual pre season shakedown. Since I have some other projects going already, I’m just going to pull the 350 this winter and clean it up and go through some things and drop it back in. I wouldn’t mind doing a few budget friendly upgrades while I have it out. If you have any suggestions I’m all ears.


If it were me....

Before pulling engine do a hot compression check.  Once apart verify compression, deck height etc and optimize on rebuild. 

Mild port work on the heads and fill the center crossover ports. -since you are going to have it apart? -

Verify cam and valvetrain, optimize for your boat if needed.

check and optimize all oil drain back locations in the block. ( how apart do you plan to go to cleaning it up? )

Check and optimize exhaust system.


  • Boat #1: '96 Laveycraft 21' XT Ski
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96Laveycraft21Xt

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Re: 403 olds is just slow?
« Reply #7 on: December 16, 2021, 01:42:25 pm »
Oh, and verify timing and that the carb is getting full throttle.  4000 still seems a bit low.
  • Boat #1: '96 Laveycraft 21' XT Ski
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BeefSupreme

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Re: 403 olds is just slow?
« Reply #8 on: February 19, 2022, 06:52:45 pm »
 I went ahead and pulled it and now I have the engine on a stand. I haven?t cracked it open yet so im not sure what previous works been done to it, if any. I hit up a local machinist about working the heads a little bit but he?s dragging his feet so I?ll probably need to find another guy. Im no engine builder so bear with me I don?t know crap about how to make power I just know how to pull a motor  ;D I just want to get more speed maybe, 55 to 60 mph and still be reliable as possible. I?ll probably tear into it this weekend or next and try to identify what the internals parts are looking like and see what I?m really working with and post a better update then.
  • Boat #1: 83 Charger
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todsme

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Re: 403 olds is just slow?
« Reply #9 on: February 24, 2022, 10:03:23 am »
I like Berkeley 12JE pumps . Had a 1978 20.5 FT. Kona mini day cruiser .Harman Ford 460 stock except 428 timing chain assembly, JE pump ,ride plate, JP marine  intake  grate,massaged hull to intake area, saddle tanks . That style pump brings the engine farther back towards the transom . Kona with no hook in the hull ,saddle tanks and no place diverter ran 55+ and got loose  on Havasu mild chop  pretty easy above 50.
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96Laveycraft21Xt

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Re: 403 olds is just slow?
« Reply #10 on: June 17, 2022, 03:32:13 pm »
I went ahead and pulled it and now I have the engine on a stand. I haven?t cracked it open yet so im not sure what previous works been done to it, if any. I hit up a local machinist about working the heads a little bit but he?s dragging his feet so I?ll probably need to find another guy. Im no engine builder so bear with me I don?t know crap about how to make power I just know how to pull a motor  ;D I just want to get more speed maybe, 55 to 60 mph and still be reliable as possible. I?ll probably tear into it this weekend or next and try to identify what the internals parts are looking like and see what I?m really working with and post a better update then.

Sorry, forgot about this site for a bit.  What did you find out?
  • Boat #1: '96 Laveycraft 21' XT Ski
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BeefSupreme

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Re: 403 olds is just slow?
« Reply #11 on: June 20, 2022, 11:49:23 pm »
Well the good news is the olds is back in the boat and just about ready to fire up for the first time this season. Unfortunately the machinist I talked to flaked on me. And after some research and shopping around i found out there isn?t a lot of parts available for the ?77-?80 olds 350?s I couldn?t even find a complete set of gaskets for a rebuild so since it seemed to run healthy before I pulled it and it looked clean inside the valve covers I decided to just clean it up and paint the block, heads, and valve covers. Put in a new valley pan resealed the intake, change the oil, spark plugs, cleaned the carb. Regular tune up stuff. Now I just have to add oil, fuel it up, do a nut an bolt check and buy a new battery or two because I?m an idiot and left  :Dignition on for weeks in before I started this projects. If my work schedule permits I?ll take the Morning Wood to silverwood lake for a test run and check timing and replace my trailer bunks while I?m at it. Once I clean it up and all back together I?ll try to get a couple of good pics to post.

Hope every one else is on the water already ;D
  • Boat #1: 83 Charger
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96Laveycraft21Xt

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Re: 403 olds is just slow?
« Reply #12 on: June 30, 2022, 11:21:29 am »
Dont feel bad.  I just took the boat out for the first trip last weekend at havasu! 

Good luck, let us know how it goes.
  • Boat #1: '96 Laveycraft 21' XT Ski
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BeefSupreme

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Re: 403 olds is just slow?
« Reply #13 on: July 03, 2022, 04:20:58 pm »
Good news and bad news. I was going to put my new plug wires on so I checked the firing order on the distributor for the first time and found out cyclinder 1 and 5 were swapped  :( so that may explain a lot. Wish I had checked that sooner. I ran new fuel lines and filter. Installed a new battery had some wiring issues. Got those taken care of and finally it was ready for a quick test fire. She fired up and ran pretty good sounded better than before with no audible misfires. Here?s where the bad news starts. I hooked up the garden hose ran in for a few minutes she was idling a little high about 1,000 to 1,100.  I assume the timing is off. Both valve covers have a small leak probably just need to be tightened down a little. Exhaust leaks on both sides. Whatever. But the main issue is water immediately got into the oil noticed it seep out of the the valve cover pulled the dip stick and confirmed milkshake.  :banghead: not sure why or how. Im hoping its something easy to fix. I really wish I pulled the whole thing apart while I had it out but I guess I know next time.
  • Boat #1: 83 Charger
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okuaskt4it

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Re: 403 olds is just slow?
« Reply #14 on: July 04, 2022, 01:42:53 pm »
Happy 4th to you and everyone else on here. Sorry to hear your troubles with the boat. Sneaky plug wires & carb issues can sound the same. When you run it on the hose do you start the engine first then turn the water on?  Then while running, do you turn water off before engine is turned off? Depending on what exhaust system you have & waterline routing, higher water pressure from house hose can make oil milky too. Hope to hear you get it figured out.
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BeefSupreme

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Re: 403 olds is just slow?
« Reply #15 on: July 13, 2022, 06:55:11 pm »
It?s been a headache. I start the engine then turn on the water. I have Hardin logs and snails plumbed pretty basic, water in from pump to logs to block out thermostat housing back to logs and out. I installed a water pressure gauge on my intake manifold but the gauge read zero even after even with the gate valve wide open. My suspicion is the head gasket or worse case a possible cracked block maybe? Any suggestions on tests to track this down or any ideas before I tear it apart again. I?m also having a hard time tracking down gaskets that will fit the engine is somewhere between 1977 and 1980 and I think only those years will fit. Correct me if I?m wrong please. Thanks every one!
  • Boat #1: 83 Charger
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Knightnight

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Re: 403 olds is just slow?
« Reply #16 on: July 15, 2022, 07:02:03 am »
Always subtract 20mph from seller top speed claims unless they can prove it via gps or your water test.
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BeefSupreme

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Re: 403 olds is just slow?
« Reply #17 on: July 15, 2022, 07:44:32 am »
Ain?t that the truth, I?m ready to just sell this boat and get a clean full stringer hull
  • Boat #1: 83 Charger
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