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Discussion Starter · #1 ·
Looking to get a 1971 Glastron V-175 super jet back on the water. This is a deep v boat used for recreation tubing,skiing etc. Currently has a Berkeley with a C impeller and a 350 Chevy. When the boat was originally done over I had no idea of how or why a jet boat works. Living in the northeast very few people did either. I had a 4 bolt main motor rebuilt. It supposedly had a higher lift cam, edelbrock performer ,and 650 holley carb. It pushed a brand new rebuilt pump with a C impeller to 4800 rpm's Good for a whopping 250 hp. This was done by a local shop that didn't specialize in marine or performance engines. The motor ran flawless for 6-7 years and finally I believe it developed a knock from a wrist pin bearing due to a small amount of water getting in. The crank bearings all looked fine. I believe the boat originally had a A impeller in it. The motor and pump were changed at the same time. The boat use to pull skiers out of the water much better even with a tired junk yard motor before the rebuild. It also was as slow or slower with the new engine and pump 45ish on the speedo. Since the motor needs to be rebuilt I am looking for more power and speed. I have read as many of the back pages on as many sites as I could find. The cost to keep the c impeller and add a inducer( I can have the shaft machined for free at work) Is about equal to getting a bigger impeller. I would like to go up to 350 hp with the 350 or go to a 383 with 400 hp. That would put me around 5350-5600 rpms on the C impeller which should get some more speed. How much does the inducer help on low end for wakeboarding,tubing,skiing etc. The current set up fell of plane easily with a load. So what would the pros and cons of a C with an inducer VS a bigger impeller be? What would anyones educated guess be on a speed increase from the 4800 rpms to the 5600 ones with the additional 150hp be. Would this also help on the low end due to more hp there also or will the C impeller only do so much at the hulls planing speed. Thank you for helping with yet another impeller question. I know its alittle bit different than the I can only get 90 mph out of my 1000 hp 600 lb boat ones. Also does anybody know of anyone in The Northeast ( Mass,Nh, Me, Conn,) area that may be of any help. The guy I used 15 years ago Kurt from Nh is no longer in business as far as I know.
 

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You would be better off with the 400 HP and a bigger impeller. The 383 you have in mind would be my choice especially with a heavy hull (of course that's what I'm running now so maybe I'm a little biased, just not in as big a boat). More displacment is always a good thing with a jet drive. A mildy built 383 should be able to turn a B or and A/B cut impeller 4800, giving you more bottom end punch and more top speed. What is the condition of the pump now? Are the clearances tight?
 

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Discussion Starter · #3 ·
The only clue that the pump is still tight is that the rpms haven't changed at all since new. It does have some hours on it but shows no signs of the rpms increasing or loss of performance. This going by memory since the boat has not run in a few years. I'm just wondering if the jump from regular rebuild at $1600 to a 383 with 400 hp will be worth the extra cost. While I like the boat it will not be a show piece like alot of the sleeker ones on these sites. It will be no different than repowering a older I/O. The saving grace was that with a regular 240 hp engine I got 6-7 years of trouble free operation with out any issues at all. I afraid if I can afford the bigger power will it last also. My brother had a late 80 early nineties I/O. I had to work on that a few times during our last vacation. Boy did that make me appreciate the simplicity of my boat. There are no electrical circuits for trim/choke,throttle position,etc,etc,etc. So repowering mine and getting a new starter and alt should bring back full reliability with out a million other items to let go every time out. ( except the usual boat things). I have seen 383 rebuild for as low as $2600 up to $5000. I don't need a top fuel drag boat just like to make sure I get the most bang for the buck.
 

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I bought my rotating assembly from a machine shop for about 800 bucks, new Scat crank, bearings, 6 inch rods, forged pistons. With machine work I don't think I had more than 1500 into the short block, including balancing, boring, I had them hang the pistons and clearance the block. I went with a roller cam, but if you don't go that route a cam a lifters wont set you back more than a couple hundred, SBC's are about the cheapest thing to build. Even having a valve job done I think you could do it for around 2K, give or take a couple hundred, even less if you didn't want forged pistons. Built conservatively should last as long as what you had. My 350 lasted for over 15 years, had to replace a piston along the way as a ring land broke, then I decided I wanted more so I built a 383, I still have the 350 short block for a spare as it was running fine when I pulled it out, and I was not easy on it at all.
 

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Discussion Starter · #6 ·
The problem I have is I don't know of any motor builders in my area that specialize in Marine applications especially jet ones. I feel they might do a great job like my last one except not hit the power characteristics I would need. I'm not knowledgeable enough to direct anyone in cam type needed or what type of pistons, rods would be of a good enough quality and still be affordable. I could be mislead easily and not get what I need. I suppose I should go talk to a few and get some info to deal with. How hard is it to hit 350/400 hp with a mild built 383. Can you get there with a mild cam/regular pistons, and not crazy priced heads. Where level does the trade off come between reliability and power. As you can tell I'm not a motor guy. Dirt bikes that's another story. That's why the boat has been sitting my 2 kids got crazy into MX racing. There went all my money and time.
 

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The parts like pistons, crank, rods, are going to be the same stuff you'd buy for a performance car for the most part, just have to pay attention to clearances since marine engines tend to run cooler and be pushed harder. Cam selection will be important, but a marine grind cam isn't any more pricey than an automotive performance grind. What heads do you have now? That will probably be your limiting factor, 350HP is an easy target even with stock heads. PM me your email address.
 
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