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Small Block

M

Mark Bennett

Member
Ok, I've just purchased a new 18'X8' boat with all stainless rigging and 3/8" polymer bottom with a crate 383 Stroker engine with a 2:1 belt reduction drive on it. Well, when I picked it up, I got a chance to run it for about 4 hours and the choke on the carburetor kept sticking and kept the motor flooded the whole time we were running it. We took a short look at it and decided it would be best to take it back to the dealer and let them look at it instead of us trying to fix it ourselves and messing something else up. Once we got it back to the dealer, they called GM about the problem and GM had them break the motor down and check several other things. Then, they put it back together and it was running around 100 lbs. of oil pressure. I'm still not sure what was wrong with it exactly. Finally, they ended up putting a new motor on the boat (which I was very thankful for) and calling me to come back and pick it up. When I get over there to pick it up, they inform me that I should never run the boat over 4,000 rpm's and to never haul more than 2 or 3 people in the boat. That's kind of where the problem came in. This boat is mostly used for duck hunting and we normally have 4 people to a hunting group. The 4k rpm's I might have been able to live with, although I don't understand it at all, but we always have more than 2 people. My question is, is there anything we can do to make this motor have better performance? I thought I was very specific when I explained to the dealer what the boat was going to be used for, but needless to say, I'm now stuck with a brand new boat that will not perform the way I'd like it to. Any suggestions would be appreciated.
 
It's an Air Ranger. They've been real good about it so far, I'm just pretty nervous about it since what happened to the first motor and now not being able to run over 4k rpm's. I was under the impresson that these high performance engines would put out more than that.
 
Faron and Stan are great honest guys, they will treat you right. You sure they did not tell you the 4000 rpm and load limit while breaking it in?
 
Yes, they've been very good to me and I think you'd be hard pressed to find a better built boat. I don't think he was talking about just breaking it in, but maybe that's the case. Once it's broken in (25 hours), how many rpm's should that motor be putting out?
 
When I had my ZZ4 and a 2 to 1 belt drive on my boat it turned 4600 and it was OK but then I did a few minor mods to the motor and re pitched the prop where it turned 5300 and the difference was like night and day most SBC produce there maximum torque between 5200 and 5300 rps and the motor was putting out 400 hp but I think you are really pushing the limits of a small block on a 18 ft boat most of the boats I have ever seen that are that size have BBC on them oh and my boat was 14 X 7.5
 
Man somethin musta got lost in the translation on this one. I never heard of dont turn over 4000 and dont haul more than 2 or 3 people especially on an 18' boat. I would be callin them up and makin sure on that stuff, its just my opinion but that wouldn't work for me at all. BETTER CHECK EM AGAIN.
 
Ok, I just called again and verified. Couple of people and 4k rpm's. I'm just wondering what kind of modifications we can do to get more from this motor, if any?
 
Hey Mark, my computer has been down so I apologize it took a while for me to see your post.

Your Engine can turn 5,000 MAX RPM's but you should not run the boat at 5,000 RPM's.

It is ideal to cruise at about 3000 to 3200 rpm's with your set up. It can be al ittle higher if you have more weight in the boat.

As for a performance boost, I would suggest a 3 blade prop if thats not what you are currently running. I thought you upgraded (last minute).

This boat should work fine for you, just remeber to keep your loads as light as possible if you want performance.

As per the original engine problem, w e called our supplier about the oil fluctuations and decided it was best to just replace your original engine so we would not end up with any problems. I want to make sure you are happy and if there is anything else you need please give me a call on my cell phone at 409-920-0716.
The Southern Airboat crew can also help with airboat questions.
 
If I was you I would talk to waterthunder but I can just about guarantee you he going to tell you it's not going to hurt the motor to turn it at 5300 I used to Cruz at 4000 rpm and I had 120 hrs on it before I put the LS 6 in the boat and never had a problem if you want more power I put 1.6 roller rockers on mine and a racing marine MSD distributor with a curve set at the lowest rpm to go to full advance at low rpm and a 850 holly carb and that gave it about 75 more hp but I was also turning 5300 rpms at full throttle but I also only had a 14 ft boat 18 ft is a lot for a SBC
 
What is the prop? ie make, size, pitch,...
A 2:1 reduction and 4,000 engine RPM's would equal 2,000 propeller RPM's, maby that's all the prop should be turned.
Maby the suggestion to keep the engine under 4K was precautionary, the engines life span would certainly benifit from not having the piss run out of it at 5K or better.
 
The best performance mod you can do for that motor is to put it on a 14ft hull. If your not going to haul more that 4 person total a 14ft would fill that bill easily. You would be way more happier. Or get a 572 big block with a counter rotator lots of bucks later you would be really happy. I'm sure Faron will make sure your happy either way you go. Faron is a jam up person. 8)
 
man I feel for you. well they have spoken.. max rpm is 5000 but don't run it there, heck even the engines in the older stock chevys were redlined at 5500 and you could run em there. Best of luck
 
That engine should turn to 5500 without breaking a sweat for short periods of time. But it wont because it doesnt have enough reduction and its a huge boat...the load is killing it. The real problem is too much hull and weight and not enough engine. You run an 18 x 8 hull with a load, you in my humble opinion, must have a big block. No substitute for cubic inches---esp in an airboat that is heavy and runs dry etc. Bottom line---trade that 383 for a 502 or a 572. You'll be shocked at the difference in power down low. Charles
 
Mark,

First off welcome to the site! Faron and Stan will treat you right and the air Rangers are awesome boats as well. Sounds like you're where I started with my boat. You might need to upgrade to get the boat to dance like you want. I started with a 350 and a 2 blade prop on my Diamondback and just wasn't happy with the performance. I too had to wind it up to 5K just to get it to move, (but don't keep them there long)! I finally changed to a CR assembly.

Do like me and try to stash money away from the wife, (so I can get one of the Waterthunder engines like Sniper has). :D

Basketcase
 
Thanks for all the tips guys. It looks like I'll be in the market for a BBC pretty quick. What all will have to be done as far as modifying the cage/engine stand to accommodate a big block engine? I realize the reduction unit and prop will also have to be replaced. Am I leaving anything out?
 
You can keep everything but the headers. Because the engineers at GM were brilliant and practical a Small block, Big block, V6 and straight six and all the LS1,LS2 and LS6 all bolt right up to the same bell housing so keep your gear box and prop the only thing you will need to change when you go to a BBC is the headers!
 
Mark

I think the best bet for you is to trade that SBC in for a BBC I don't even think one of WaterThunders LS ENGINES would do what you need when you get a boat that big a BBC is the way to go Bigcvr has a 502 on his boat and it is a hoss and he runs the heck out of it and he has a 2 to 1 belt drive on it I believe and the boat really runs good and Airboat4fun has a bbc on his boat as well and I cant remember either one of the ever saying they ever had any problem out of them
 
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