No updates on the motor as I wasn't able to go out on the water this past weekend but I did bring the boat home to get some work done.

Does anyone know what these thing are on the bottom of the hull right by the pump. There is one on each side and they are about 6-8 inches long. Looks like a half round piece of pipe filled with silicone

hey just a thought how do your valvesprings look? If one or two are weak they could be floating causing a misfire ? Hmmm

The motor runs strong up to 4200, I am just trying to get a couple more rpms out of it.  I don't think there is a hardware issue, just something with the timing/fuel. 

I am going out next weekend and plan to bump up the timing a lil more and add more jetting.  From there I will get a chance to check the plugs and try to dial it in.  Either way I am bringing the boat home after this next trip and have plans to take it to GS Marine to have the pump gone through.  I will have Greg dial in the carb (or diagnose another issue) at the same time.  She should be ready to rock some trips to Elsinore before too long.

Disclaimer: I've only played with BBCs in cars, not boats... what I'm about to say applies to automotive but I don't see why marine would be different.  The following is based on the distributor having a mechanical advance, not electronic...


A typical GM HEI should have more like 14-18^ or so of advance from idle (I've seen it vary from model to model) .  If base is set at 20 you should see 34-38 total at 3000-3500.  Depends on weights, springs and stoppers.  If you're only seeing a 4^ advance it sounds like the mechanical advance mechanism is stuck, possibly corroded given that distributor is locked in place to the block. 

That being said, 24^ sounds awfully low to me.  Street cars with pump gas and 10:1 compression usually run in the 32-34 range as a starting point and dial it in from there.  The 1st thing I'd do is check to make sure the advance is working correctly and try adding some timing.  Go in small 2^ increments and see how that affects the top end.  Check plugs for signs of detonation between adjustments.

I've seen this type of issue in automotive a few times and this was the answer, but like I said I've not run a BBC in a boat.  Guys with more marine experience please correct me if this doesn't apply. 

All good ideas but this is a 8 pin hei. All electronic so there all no weights it's all build into the module. I may bump up initial timing a bit more but she is for sure starving for fuel.




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What was the vacuum at the highest throttle setting?

The power valve does not need to be higher vacuum. There is very little engine load at 6.5" hg.

A jet boat engine has a linear torque curve, so the engine load gets higher as the revs go up. Once the torque is exceeded, acceleration stops.

What was your fuel pressure at WOT? I don't care if you leave the jets out of it completely, if you don't have the fuel volume/pressure, it will ruin itself out of fuel.

GT

Unfortunately I don't know what the vacuum was at when I was WOT, all I have is a handheld vacuum gauge which I used to set the air bleeds.  I could try to get a length of hose and bring it up to the front of the boat to have a look while I am driving. 

Also, I wasn't able to get a look at the fuel pressure gauge while running WOT, it was at 6psi at idle but I know that means next to nothing.  The fuel pump is a carter vane style which I assume is original to the boat. 

As I mentioned earlier the motor felt a lot stronger with the new carb and changes so I think I am close.  I have been planning on taking the boat to a professional over this winter for a once over, so I may leave it in capable hands to fine tune the carb.

GT as always I appreciate your help, and I will update if any changes are made.

We are in the exact same situation. My 454 tops out at 4200 as well. I will keep you updated with what works for me. Next trip out I am changing the ignition module, flame arrestor and hopefully carb. I'll let you know if I am able to spin more rpm.


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List number 9022.

This is like asking if you have the right shoes on.  Lol

What is the list number?

GT

I have some updates since I was able to work on the boat a bit this past weekend.

I replaced the fuel filter checked the timing, these were the two main things I was looking to get done.  At idle the timing was around 20 deg advanced (I don't know for sure since the indicator stops at 16).  With the timing shunt plugged into the dist the initial timing dropped to 8 degrees, unfortunately the dist was locked in place due to corrosion so I couldn't adjust the base timing up to 12 deg (1st fail).  Knowing that I couldn't adjust the base timing I decided to check the advance as i revved the engine.  Around 3k it moved up a little but probably only up to 24 deg, this was showing total advance from 20 ish at idle to 24 ish at 3k RPM.  This has me thinking the module is bad so I already ordered a replacement.

The boat runs well enough so I took it out on Friday and it ran the same since the day I got it.  Fires right up and limits out at 4200 RPM. 

Saturday morning I decided to put on the new to me Holley 750 DP and hoped that would make some improvements that day on the water.  Once it was all plumbed up I turned the key and gas was just pouring out of the J-tube (2nd fail).  The front float appeared to be stuck, and no matter how much I smacked the carb with a wrench it just did the same thing.  So the new carb came off and the old one went back on. 

The boat runs fine and she was always meant to be a cruiser so I hope I am not chasing more RPMs and throwing parts into her if there will be no change in the end. 

At this time, I have a new flame arrestor ordered (thinking the one on there may be limiting air flow).  A new ignition module on the way, and the new carb will be rebuilt soon.  All those parts will get changed out, and I will adjust the base timing when I hit the water in a few weeks so hopefully there is an improvement then. 

Does anyone know for sure if I need to use a HEI initial timing adapter described in the two below links to set the timing?  I have a small cap HEI with the 8 pin module.

http://www.marinemechanic.com/site/page229.html

http://www.boatfix.com/merc/bullet/90/90_15.pdf

If I do need this plug does anyone know where I can get one?  I cannot seem to find it for sale anywhere.

I started a topic a couple days ago in the "Jet" area but it sounds like I have more of a motor issue if anything.

I have a 1996 (hull number says 95) Hardin Caribbean open bow with a Hardin 454.  There is no hour meter and the prev owner did not have any records of motor work; so I have to assume all the internals are original and probably pretty tired.

Right now the revs top out at 4200 and the issue could be any number of things. Below is what I know for sure and I will update as I find out/diagnose more.

Carb: Holley 750 with vacuum secondaries - Hoping to switch to a double pumper so I can know for sure that the secondaries are opening. 

Distributor: Small cap HEI with the 8 pin module - When adjusting the timing can I just loosen the hold-down bolt and turn like a conventional dist?  I have read that I need to plug into a computer but I don't know if that is only for EFI systems.

I will check the flame arrestor to see if it is dirty and clean/replace if needed.  The fuel filter likely needs to be replaced as well so I will take care of that next trip out.

Right now the boat is stored at Lost Lake so I can only get out there to work on stuff every so often.  I am planning on bringing it home after this season to have a shop give it a once over.  The shops that I always see pop up are GS Marine and BJs Marine in Anaheim.  Are there any other reputable shops in the area that would be able to diagnose and repair the motor issues if I cant figure it out?  I appreciate all the help as I am trying to learn as fast as possible; I came from the classic car world so much of this is new to me.

Thanks!

This gives me a place to start, I'll look into it.

Thanks!

I got my boat a few years back and it would lay down around 4200 rpm also. I found out it wasn't advancing the spark at all.. It needed a module in the distributor is all, so you might check to see if timing is advancing

Hi All,

First post here and new to jet boat community.  I bought a 1996 Hardin Caribbean open bow a few months ago and unfortunately the old owners did not have much information regarding rebuilds/pump work.  The boat runs good but there is no indication of a pump rebuild so I am thinking of having someone give it a once over after this season. 

Here is what I have gathered so far.

Engine: 454 with Holley 4010 750 CFM carb - Max RPM 4200

Pump: Berk 12JG-A - Does this mean A cut impeller?

Max MPH on my phone was 43MPH

When up on a plane the boat rides extremely low in the water, do you think a droop and or place diverter would help to get more of the boat out of the water?  Also, I am a bit confused with the different cuts of impellers; I'm guessing the motor makes around 300HP and it's max RPM is 4200.  Is the A cut impeller the best. 

Ultimately, if/when I get the pump worked on I would like a little more top speed (not sure if that is possible without more HP) and I would like to get more of the hull out of the water. 

Thanks for the help and I will post pics as soon as possible.

Interesting looking transom. Looks really clean from the pics. Don't see too many jets with the steering on the right. Was it a conversion that you know of?


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I don't know anything about it yet. I just came across it today, I will ask some questions tomorrow. I am just worried that I can't find any info on the manufacturer.

Here's a link to the add: http://www.boattrader.com/listing/1996-Allen-Boat-Co-Open-Bow-367032