[millwrightlong]

first i am new to forums so please help me out with any tips you may have.

I have a 73 18' Sanger super jet with 455 olds and Berkley jet. The 455 was rebuilt 5 years ago but only has 30 hours on it. It has a Holley dual inlet square bore with vacuum secondaries. aluminum intake. HEI ignition. mild cam with light lope but still great idle. 9.5 to 1 pistons. Berkeley wet logs.

The problem is that the boat will not rev over 3500 rpm but has more throttle. i can get 3900 when cold. Once i reach 3500, if i give it more throttle it bogs just a little to 3200 and stays there untill i back off. compression is good, plugs, wires good.

 

[jetboatperformance]

first i am new to forums so please help me out with any tips you may have.

I have a 73 18' Sanger super jet with 455 olds and Berkley jet. The 455 was rebuilt 5 years ago but only has 30 hours on it. It has a Holley dual inlet square bore with vacuum secondaries. aluminum intake. HEI ignition. mild cam with light lope but still great idle. 9.5 to 1 pistons. Berkeley wet logs.

The problem is that the boat will not rev over 3500 rpm but has more throttle. i can get 3900 when cold. Once i reach 3500, if i give it more throttle it bogs just a little to 3200 and stays there untill i back off. compression is good, plugs, wires good.

Welcome to the boards , assuming your Tach is correct the first place I'd check is fuel supply , eg: contaminated fuel , resticted lines , restrictive filters and pickup tubes , fuel pump pressure and volume ?? The fact that you "back off" and it maintains suggest to me that your asking it to do more than your fuel supply might allow Could also relate to internal Carb issues as well feel free to call if we can help Tom

 

[millwrightlong]

The tack is right, i forgot to mention that i have tested that. carb has been rebuilt with the same results before and after. all lines and filter have been replaced with same. had spare mech fuel pump so switch that.

 

[slowride]

first i am new to forums so please help me out with any tips you may have.

I have a 73 18' Sanger super jet with 455 olds and Berkley jet. The 455 was rebuilt 5 years ago but only has 30 hours on it. It has a Holley dual inlet square bore with vacuum secondaries. aluminum intake. HEI ignition. mild cam with light lope but still great idle. 9.5 to 1 pistons. Berkeley wet logs.

The problem is that the boat will not rev over 3500 rpm but has more throttle. i can get 3900 when cold. Once i reach 3500, if i give it more throttle it bogs just a little to 3200 and stays there untill i back off. compression is good, plugs, wires good.

I've run Holleys with vacuum secondaries in the past, but am not a fan. That said, it may be something as simple as a ruptured secondary diaphragm that is keeping the secondaries from opening. A quick way to test it when you're out is when you are at full throttle, have someone move the diaphragm shaft up opening the secondaries. If you pick up rpm, you know to concentrate on the diaphragm circuit.

 

[millwrightlong]

I am feeling a little stupid right now because of overlooking the obvious. This boat has dual aluminum tanks. It has a fuel filler cap on both sides, but the though occurred to me and so i looked and cannot find any vents for either tank. It seems that this boat never had any vents installed. Is my thinking correct in assuming this could be a problem?

 

[millwrightlong]

yes i thought of that. i put a spring on the secondaries to make sure they open. infact they do with same results.

 

[Mohavekid]

the tanks are probably vented tru the cap. Check for a small 1/8 inch hole under the cap. You might need to add additional holes.

 

[Sanger Pete]

I had the same problem years ago--turned out to be a plugged/clogged fuel pickup in the tanks that restricted the flow. I isolated the problem by running the fuel hose down the fuel fills, and viola, 5000 rpms. A fuel pressure guage would also help.

 

[1975sleekcraft]

first i am new to forums so please help me out with any tips you may have.

I have a 73 18' Sanger super jet with 455 olds and Berkley jet. The 455 was rebuilt 5 years ago but only has 30 hours on it. It has a Holley dual inlet square bore with vacuum secondaries. aluminum intake. HEI ignition. mild cam with light lope but still great idle. 9.5 to 1 pistons. Berkeley wet logs.

The problem is that the boat will not rev over 3500 rpm but has more throttle. i can get 3900 when cold. Once i reach 3500, if i give it more throttle it bogs just a little to 3200 and stays there untill i back off. compression is good, plugs, wires good.

the interesting part of all this is you are right at where my secondaries open 3500-3900rpms.
does it pop through the carb when you atempt to give it more throttle??
it is my belief that you are running on primaries only.

 

[millwrightlong]

the interesting part of all this is you are right at where my secondaries open 3500-3900rpms.
does it pop through the carb when you atempt to give it more throttle??
it is my belief that you are running on primaries only.

It does not pop. i put a spring on the secondary to make it open right away such as a mech secondary would. it ran much the same, no pop, just a slight bog from 3500 to 32 to 33. I have replaced everything from lines, filters, pump. had the carb rebuilt. the next thing i plan to do is clean out the pick up screens and i am going to swap out carbs, first one then the other to see if i can pin point the issue. Other than that, i will do every test posible to run this down. the only other tell tale thing i noticed when i had it out tonight was a high pitch whistle when i hit just at 3500. i had someone else drive while i watched. but i dont beleive i am getting much if any fuel in the secondary. i get fuel when i actuate it by hand while shut down however. i think it is somthing wrong in the carb and i will see with the carb switch over soon.

 

[T-Train]

It does not pop. i put a spring on the secondary to make it open right away such as a mech secondary would. it ran much the same, no pop, just a slight bog from 3500 to 32 to 33. I have replaced everything from lines, filters, pump. had the carb rebuilt. the next thing i plan to do is clean out the pick up screens and i am going to swap out carbs, first one then the other to see if i can pin point the issue. Other than that, i will do every test posible to run this down. the only other tell tale thing i noticed when i had it out tonight was a high pitch whistle when i hit just at 3500. i had someone else drive while i watched. but i dont beleive i am getting much if any fuel in the secondary. i get fuel when i actuate it by hand while shut down however. i think it is somthing wrong in the carb and i will see with the carb switch over soon.

Did you do the rebuild on the carbs? I had my carb rebuilt because i didn't have the time. When i went out to the lake and ranit it ran fine. The second time out it did what yours is doing. When i took the carb apart i found silicone stuck in the jets. I will find time from now on. Good luck

 

[millwrightlong]

Did you do the rebuild on the carbs? I had my carb rebuilt because i didn't have the time. When i went out to the lake and ranit it ran fine. The second time out it did what yours is doing. When i took the carb apart i found silicone stuck in the jets. I will find time from now on. Good luck

no i did not. i had it done.

 

[SS 201]

Do you know someone with a carb you can use to eliminate its a carb problem?

 

[T-Train]

no i did not. i had it done.

I would pull your bowls off and check your jets. Make sure everything is ok.

 

[Widetrack]

Just a thought! Some times an HEI will stick in a locked out spot with rust,ect. Just pull the cap and see if the rotor will move like to advance timing. If not you are not getting full advance or are full advanced all the time, and it is an easy fix! This is just something to look at! It does all sounds like carb or fuel issues anyway! WTdevil

 

[rangerrob]

X2 my olds was only getting 32 degrees, bumped it up to 36 and gained 400 rpm.