Need more speed

[rick1964]

Hi I'm somewhat new to boating, i bought from a buddy a 1970 18' schuster tahiti torino, it seats 6 to 8. The hardin marine 454 had to be rebuilt as well as the froze up berkeley 12je pump. My problem is that I can only get 54 mph gps out of the thing.... I think the motor has a mild cam in it. I'm not sure if the impeller is matched to the engine, my tac as well as my ear says the engine is only turning around 3000 to 3500 full throttle with a new holley 870 on it. Cant get anymore out of it. The engine has 8 hours on it so far... I had the heads ported and polished and have a mild high rise intake... Seems to me that motor should be pushing a little harder than that.... then again maybe not...... I'm thinking at that rpm the engine isn't reaching its power band...?

[shaun]

Rick,

3000-3500 RPM is cruising rpm for me, your definitely not even close to waking that engine up. Who did the pump work, do you know what impeller they put in the boat? I would check a couple things. First check to make sure your throttle linkage is setup correctly so that the carb is fully open when the gas peddle is mashed. Also make sure your secondary's are opening properly, most of us boat guys run mechanical secondarys but if you got a vacuum deal make sure they are opening.

[rick1964]

Hey thanks for the reply, I set up the carb myself and the butterfly's are opening fully, I do have vacuum secondaries, they too are opening fully, as I had someone drive it full throttle whilst I checked, I even pushed on the secondary diaphragm linkage while running wide open to make sure they didn't open any further, its runnin full tilt. Im in San Diego near lakeside, I actually had to have the pump replaced with the same because the old one was so froze together they couldn't get the u joint off of the input shaft to get the thing apart. The work was done at JP marine in lakeside. I called him, he wants me to double check my rpms again and go from there. I have doubts about the tac that's in it, but my ear doesn't lie. There's no way that motor is turning anywhere near 4500 to 5000. I asked JP marine once before and he said they put a standard impeller in it. That doesn't tell me anything,,, I'm going to give them a call again. I had the motor rebuilt at Ricks machine in lakeside, they're good guys. The timing is at 32 degrees advanced throttled up. As high as it can go im told.. flame thrower coil, no ballast resistor, new plugs. 2 batteries so I can start it advanced. Should I always run premium in it? How much of a difference is it.... I don't think I had premium in it my last run first of november.

[shaun]

You need to find out what impeller is in it and what cut. The 12je pump is not the ideal pump for a performance deal but at the same time it doesn't sound like your cavitating the pump which means it's handling the HP no problem. I would get a new tach so you can be sure of your RPM. if you were running in the 4000's i'd say your cut is probably just too aggressive for the HP the engine is making. How much HP did the shop think your motor was putting out and at what RPM?

I wouldn't mess with the timing, it's not going to make that much of a difference. 32* all in on a naturally aspirated BBC is pretty normal/conservative, really it depends on the build.

Whether or not you should run premium again depends on the engine build. Running premium is not going to increase horsepower, in fact it does the opposite. You only need higher octane fuel if your engine's compression is higher and needs it to prevent detonation.

[rick1964]

Well i stand corrected... It seems i have a 12jg-a pump in my boat. Is that a good pump? Still not sure of the impeller size but I will call JP marine later...Maybe that's what the "a" means. Hey I just got a 50 dollar gas card for Christmas!! That's good for a 2 or 3 hour run! LOL

Also, Do you think a high rise intake manifold would make that much more power?

[shaun]

A 12JG pump is good, there are better pumps but you only need to go that route when making serious power. The A stands for the cut impeller that was originally in the pump. A is an aggressive cut and unless your making some good power your not going to be able to spin it very fast. In a stock application you would probably spin that impeller around 4000-4500 RPM. I'm spinning an aggressor A+ impeller 5400 RPM in my boat and i'm pushing close to 700 HP. You can have the impeller cut to match your application, there are advantages and disadvantages when doing that.

A high rise intake manifold will probably help make a little more power, but i don't think it's going to be noticeable.

Do you have any pictures of the boat? What are your goals with this boat?

[shaun]

Here's an impeller RPM to HP chart for berk impellers

http://www.riverracer.net/forums/attachment.php?attachmentid=192&d=1356549713

[rick1964]

Yes I'll get a picture of the boat to ya... How do I upload one here? The chart is very helpful. Thanks, Are you in San Clemente? Thats not too far from me... Im in La Mesa...

[shaun]

When you post, there is a button above the box where you write, it looks kind of like a picture frame and when you hover over it, it says "Insert Image" click that, then click the browse and select your image from your computer.

[rick1964]

Hey Shaun, I'll upload a picture or 2 soon. Im just curious how many cubic inches is your motor. Is that your boat in your picture? What kind of build did you do, and did you do it yourself? I do know that when the shop had my motor apart I did see that it is a 2 bolt main.... How far do you think I can take a 2 bolt motor in hp? Im thinking before I go messing with the impeller would it be better to build on the motor, like put a better cam in it to start. Then match the pump to it. I could drop another 1000 or 2 in it over time to beef it up more...

[shaun]

Yep, thats my boat in the avatar. When i got it, there was no engine and it needed alot of work. I fully disassembled it and started from scratch doing everything I could myself. The engine is a 4.25 stroked 454 thats .070 over, so it's at 498cid. The 2 bolt main wont really be a problem until you start making some bettter power or start pushing some higher R's. I'm guessing 500HP+ or 5000RPM+, i'm no engine expert so don't hold me to this. If you plan on making more power i wouldn't mess with the impeller until then. I still think you should find out though whats in it. With a cam be careful not to go too big, boats, especially jet boats are a whole different animal. I would maybe call Clay Smith and talk with him, If i remember correctly he has cams designed to work well with mild 454 BBC's

Clay Smith Cams 5870 Dale Street Buena Park, CA 90621. Telephone: 714-523-0530. Fax: 714-522-3315

[rick1964]

193194195Hey Shaun I just got back from vacation, here are the pictures of my boat. You live in sd right? We should run boats together one day maybe..

Later
Rick