Big Proplems with my Boat

[zerocool5088]

I bought a 1991 19.2 ft Century that was originally stolen and stripped. Then it got a Chevy inline 6 it had mercruiser written on it and has a mercruiser outdrive. The block cracked so I just swapped the blocks for one from a 50's truck. The outdrive just broke, the housing cracked down by the prop. I am not sure what outdrive is on it i was told it was a 1970's that was rebuilt and repainted. I want to rebuild the motor and squeeze every ounce of power out of the sucker. 1)How do I squeeze every ounce of power out of that engine. 2) What do I need to get the outdrive going once I rebuild that motor. Someone please help me I know plenty about fixing motors but this is my first boat. I want to go fast, how do I do it, buy another boat?

 

[Trent]

Re: Big Proplems with my Boat

Buy another boat, your not going to get much more out of it other than propping and having the correct gears in the outdrive. The inline 6 (165HP) Is a great engine. But Hp is the name of the game.

 

[mkast]

Re: Big Proplems with my Boat

I read this articule<br /> http://www.boatingmag.com/article.asp?section_id=8&article_id=483 <br />After bolting 95 more hp in the boat, it went 7.3 mph faster. Your boat is not as heavy as the test boat, but you're not going to get an extra 95 hp out of the six either. If you want to go fast, big V8's, big wallets.

 

[Walt T]

Re: Big Proplems with my Boat

Yep, you got big problems allrighty

 

[rodbolt]

Re: Big Proplems with my Boat

hello<br /> I will ask you like I used to ask the drag racers.<br /> speed costs money. how fast ya want to go?<br /> good luck and enjoy the ride

 

[zerocool5088]

Re: Big Proplems with my Boat

Ok the buy another boat was a joke. I was kinda looking for some advice on how to squeeze all the power I can get out of what I have. I can't really afford another boat I am a poor college student. I have the knoweledge to rebuild the engine if I knew where to get the top-notch marine parts that I need. I also need a recomendation on the right outdrive for that motor since the one I got is broke.

 

[Walt T]

Re: Big Proplems with my Boat

Right here at i boats, they'll sell you a drive. Hopping up I-6's is generally not done. For speed I would suggest going to a 350 with a Bravo.

 

[LubeDude]

Re: Big Proplems with my Boat

I see where you are coming from even if others do not. You simply want what you have and want it to run the best it can. Right?<br /><br />OK, When you rebuild the engine, which you should, use all marine gaskets and copper freeze plugs. Also install the Marine cam with new lifters out of the old Marine engine you had if it is still good. Try and find a Pertronix electronic ignition modul for it to convert it to electronic ignition. Look on Ebay or swap meets untill you find a used four barrel manifold for your engine and buy a marine Carb for it, (also on Ebay). Aslo a spark arrestor, coastguard approved for same. If you can afford all this you will have all you can get out of it.<br /><br />Good Luck

 

[zerocool5088]

Re: Big Proplems with my Boat

Finally some one understands what I am going for. I am not looking to make this boat a cigarette boat. If I wanted to get a 350 and Bravo which would cost me at least 4k to get and install then I would just buy a new boat. I just want to make what I have the best as possible. Is there a place to find all the marine parts I need for my motor. Cam lifters pushrods freeze plugs gaskets etc. Anyone got the the intake that I need?

 

[LubeDude]

Re: Big Proplems with my Boat

Like I said earlier, that intake would be too expensive to buy new if they still make it, Ebay or a swap meet is going to be your best bet!

 

[rodbolt]

Re: Big Proplems with my Boat

hello<br /> I understand what your trying to do. we are just trying to politly tell you it cant be done for your budjet. 4K for a 350 with a bravo? its either stolen or blown. that package is about 13K new.<br /> what we are trying to tell you is the 250 cid inline GM 6 cylinder has been out of production<br /> for merc since the late 70's. while it was a good stout engine its popularity was not as good as the 4 or the v8. parts are getting hard to find and outragously expensive when you do. I bought a manifold and riser for one in 97 and it was almost 600 dollars. and in our salt pond they only last 4 or 5 years. what you need to do is part yours out and go find another.<br /> I have an 88 19 galaxy with a 4 that I would love to have someone else make it their project. we are not bustin your chops just trying to warn you that marine parts are expensive and you get what you pay for.<br /> good luck and keep posting

 

[Walt T]

Re: Big Proplems with my Boat

You da man Rodbolt.

 

[JasonB]

Re: Big Proplems with my Boat

I too am one who just tries to make what I have as good as possible. From what I have read over the last couple years, upping the power of your I-6 isn't easy. LubeDude had some good suggestions. I have a Mercruiser powered by a Ford 302 which some consider to be a forgotten child, but parts are still easy to find. Many of the internal parts may be available at somewhere like northernautoparts.com. The sterndrives that Iboats sell are a decent deal. You probably need a 1.67 to 1, but I may be wrong. Memory is fuzzy today. Ebay is a great source for parts. It's a doable project, but will require lots of work. The drive is easy to replace. About 8 bolts if memory serves. Some day I will learn how to rebuild one....<br /><br />A lot of speed (35-40mph maybe??) isn't in your boats future, but it sounds like a comfortable fairly effecient cruiser.

 

[FreeBeeTony]

Re: Big Proplems with my Boat

I recently rebuilt an IL6 myself: new pistons/rings, bearings, lifters, bored out 0.030, new oil pump, petronix conversion kit, etc...<br />I was interested in "fine tuning" it for more power but it doesn't look like there is any way to get more power out of these engines. They are ranked very high in reliability and parts seem to be readily available. The only thing I was thinking of trying was the 4bbl carb. Which 4bbl would fit? Would this require a different cam?

 

[cjflanagan]

Re: Big Proplems with my Boat

Calculating Needed Carb Size:<br />1)250 CID / 6 cylinders = 41.66 CI per cylinder<br />2)41.66 CI x 3 = 125 CI (remember on a 4 stroke- 6 cylinder engine only 3 cylinders fire on one revolution of the engine)<br />3)125 CI / 1728 CI = .0723 CF(convert cubic inches to cubic feet) <br />4) So now we know that for every rotation of the engine, it draws .0723 cubic feet<br />5).0723 x max rpm (say 4500)= 325 CFM<br />6) A small 4 bbl is 600 CFM, an excess of 275 CFM<br /><br />What is needed:<br />Figure out a way to increase the displacement to suck up the extra 275 cfm of air/fuel. To do that, you will need to add approximately 100 cubic inches to the displacement either through bore, stroke, or a combination of the two. <br /><br />Would need more cam? - Assuming you did everything above, yes! You would need that cam to move the increased volume of air and fuel through the valve train. But don't stop there, you'll need more spark to burn that gas, more fuel pump flow, more cooling. Thats about it.<br /><br />Or you could get a 350...

 

[affa]

Re: Big Proplems with my Boat

Hi<br />Ive read here in this forum earlier that syntetic oil and making sure the intake get as cooled air as possible are some off the simple thing that can help you getting more out of your engine.<br />Regards<br />Affa

 

[FreeBeeTony]

Re: Big Proplems with my Boat

BP212, if your calculations (formulas) are correct, a 350 would only draw 455 CFM (assuming it fires on 4 cylinders per revolution).<br />I just want to make sure I understand your theory.<br /><br />Don't the V6's have a couple of configurations where the only difference is the carb (2bbl vs. 4bbl) and the increase in horse power is ~170-200?

 

[zerocool5088]

Re: Big Proplems with my Boat

Ok, So I know that my boats motor sucks and that I can't do much to spice it up. So here are my new options and I want to know whats the best deal. I found a rebuilt marine I6 for like $1300 bucks to my door. I also found a 165 hp I6 with matching sterndrive delivered to my door for $1675. I also had the revelation if I was going to replace the engine I might as well put what was suppossed to go in it. 4.3L V6 engine. My question is stay with the I6 deal I found or try and find a 4.3 V6 setup which is better and whats gonna be the cost difference?

 

[JasonB]

Re: Big Proplems with my Boat

The V6 may require some reworking of the engine mounts on the stringers. I would probably go with the I6 as it will bolt back in. Conversion would be expensive.

 

[cjflanagan]

Re: Big Proplems with my Boat

FBT - <br />486cfm @4800rpm. Two of the most over done modifications:<br /><br />Too much carb for the wot rpm range<br />Too much cam for the wot rpm range<br /><br />350 cid @5900rpm cfm 600<br />350 cid @6400rpm cfm 650<br />350 cid @6900rpm cfm 700<br />350 cid @7400rpm cfm 750<br /><br />The difference is the internal engine components which allow for greater wot rpm.