i think my 3.0 is blown. can i go to a 5.7?

[alilley]

ok so let me start off my saying this. i have a 1988 sunchaser 3.0 mercruiser with alpha 1 out drive. it was one of the craigs lists deals. i bought the bopat for a grand. the interror is in very good shape and the floor had been replaced. i have gone through and fixed most of the small issues that an older boat can get. when i bought the boat i was informed that iit had a cracked block. i figured that i could try the glue back together bethod, that did hold for running on the muffs. now when i run it on the water at w o t i am only getting just shy of 4000 rpm. and the bildge area fills up with water in about 15 min. kick the bildge on and in no time it pumps that out.

i am mechanically enclined and i could change the motor out myself and was wondering what my options are? do i go back to a 3.0? if so do i find a new or rebuilt? or what about finding a new block and put all of these parts in it? now the back of this boat has plenty of room to support a v8 and that would be sweet. other then changing the motor mounts, the exhaust, and that kins od stuff can i put a v8 up against an alapha 1? if so can i use an auto block and slightly build up a 5.0/5.7 as long as i run a marine cam? or does any one have any other suggestions??

we really do enjoy being out on the water and dont want to toss the boat to the side i would much rather fix what we have insted of starting over. and once again many thanks in advance

 

[alilley]

Re: i think my 3.0 is blown. can i go to a 5.7?

i did forget to mention that i am noticing that there is what i feel to be a good amount of air coming out if the top of the valve cover for what is the crank case vent

 

[Adirondack]

Re: i think my 3.0 is blown. can i go to a 5.7?

From what I understand the alpha 1 will handle a 5.7. I have never done it, but I did look into it. No matter what way you go as far as used motor, or new it won't be cheap. Those manifolds, mounts, risers, and pipes cost $$$$$.

If you stay with the 3.0 your almost stuck with buying a new longblock. I have been looking, and can't find a used, or new shortblock outside of buying another beat boat with a "known good block??" Tuff motor to find.

I'm surprised you had a problem plugging the crack. JB Weld has done a good job for me. You just have to clean the surface real good with a grinder, then grind the crack into a bit of a V. Mine has held all year, and from what I hear from others it should hold a lot longer.

 

[xeddog]

Re: i think my 3.0 is blown. can i go to a 5.7?

I'm not an expert here, but I have a couple of questions.

• Is the boat rated for the hp that a 5.7 puts out?
• Would an extra 100-200 pounds cause any balance problems?
• Would you have to change out all of the controls and possibly wiring harnesses too?
• How much fuel does your boat currently carry? Enough to feed the 5.7 for the whole day?
• How much is the boat worth? Enough to justify the 5.7 and all of the additional work to get it put in?

As for an automotive engine, you can do it, but it isn't a good idea. There are more differences than the cam which is probably the least of your worries, and a lot more than just the basic engine to consider. Brass freeze plugs, SS head gaskets, different intake manifold gaskets, and in some cases even different pistons. You would also have to buy all new marine electric accessories like starter, distributor, and probably alternator unless you could reuse the other one. Most likely a bit of work to bring the fuel system up to marine standards so new fuel lines (can't use just any old tubing, and the ends of rigid tubing have to be double flared), fuel pump, and carb.



Just for starters.

Wayne

 

[wire2]

Re: i think my 3.0 is blown. can i go to a 5.7?

What length is a 1988 sunchaser? If it's less than 18', a 5.7 will tilt the stern low in the water and the package will be overpowered, a safety issue.

The other consideration is gear ratio; a 3.0 will be 2:1, a 5.7 is ~1.5:1.
Yes, you can sort of compensate with prop pitch, will need to go up by 33%.

 

[Maclin]

Re: i think my 3.0 is blown. can i go to a 5.7?

Converting from 3.0 to 5.7 is not a good plan. Those engines are around, so just fix what is in there the right way and sell it and get what you want.

 

[Alpheus]

Re: i think my 3.0 is blown. can i go to a 5.7?

There are more differences than the cam which is probably the least of your worries, and a lot more than just the basic engine to consider. Brass freeze plugs, SS head gaskets, different intake manifold gaskets, and in some cases even different pistons.

Cam is just a truck/RV cam

Nothing wrong with putting an auto short block into a boat. If its out of a truck,change the core plugs to brass and run it. No special cams,gaskets or pistons.

Having said that you wont find a 3.0 in any car or truck. They come in boats,forklifts,generators, etc...

 

[alilley]

Re: i think my 3.0 is blown. can i go to a 5.7?

the boat is 17footer and it is one of the wider tri hulls. is it still going to sag in the stern area to bad??

what i was kind of thinking along the lines of somthing like this. a budy of mine came across a 5.7 that he stripped all the marine parts off of (which he still has). getting thoes parts. i have a 5.7 motor that is standard bore with a good block, heads, and crank (it burned a hole in a piston). i have a good set of piston and rods out of a dirt track car but they dont have to much of a dome on them and with the head that i have coompression would prob be done about 9.75. i was thinking about using the head gaskets that they use on blower motors ( i think they are made of coper) so i would think it would hold up to the constant load. as far as motor mounts i was looking at it today and figured that i could build a plate that would mount to the "new motor" and use square tubing to extend foward to the stringer where current motor mounts. i dont know if it would fit or not but if i could reuse the current fly wheel that why i would not have to worry about having to get a coupler.

am i going to run into issues doing it this way or would i be better off trying to find me a short block 3.0 (currently tops out about 25 mph) or would this idea work wit out to many problems or drive ability issuers??

 

[alilley]

Re: i think my 3.0 is blown. can i go to a 5.7?

what about going to a 4.3?? if weight is going to be an issue then would a 4.3 he better off?? it is not that i a just trying to go to a bigggerr motor it is just what i have available from auto's that i have taken apart now i do know that there are some differances between an auto motor and a marine one but as far as i know the bigges is the cam shaftand and then the exhaust manifolds

 

[Alpheus]

Re: i think my 3.0 is blown. can i go to a 5.7?

what about going to a 4.3?? if weight is going to be an issue then would a 4.3 he better off?? it is not that i a just trying to go to a bigggerr motor it is just what i have available from auto's that i have taken apart now i do know that there are some differances between an auto motor and a marine one but as far as i know the bigges is the cam shaftand and then the exhaust manifolds

Like I said before. If the engine is out of a truck the cams are the same. The exhaust manifolds will not work...

 

[thumpar]

Re: i think my 3.0 is blown. can i go to a 5.7?

I am with some of the other people here. I would get the 3.0 figured out and sell it. It will be spendy and alot of work to convert over. The outdrive gears are not cheap either. If you sold it you could even buy a boat with a blown 5.7 since you have one already.

 

[AdellAdam]

Re: i think my 3.0 is blown. can i go to a 5.7?

I've been pricing out switching my 3.0L to the 4.3L. So far I found a used truck motor for $175 (it's a little beefed up...), used exhaust components for $150, and NEW outdrive gears for $175. I still need to switch to brass freeze plugs and re-do the motor mounts. I might need to get an electric in-line fuel pump as well. There's a bunch of little things to work out, but my 3.0L might be cracked and it's much cheaper for me to go 4.3L than finding a good 3.0L

 

[Alpheus]

Re: i think my 3.0 is blown. can i go to a 5.7?

Dont forget. You must use a marine carb,distributer,alternator,starter...

Also with a couple of mods you can use your wiring harness...

 

[LAC_STS]

Re: i think my 3.0 is blown. can i go to a 5.7?

Where did you find drive gears for $175 new???

I could be wrong but all the gears I think your mistaken.

 

[AdellAdam]

Re: i think my 3.0 is blown. can i go to a 5.7?

http://www.amarket.com/im184.htm

If i'm not mistaken that is all I need to change. Maybe I'm missing something...

I plan on using my old alt and hopefully the starter. The starter is almost new and hopefully I can figure out a way to mount it to the 4.3L. If not I could just sell it. I know i can use my old wire harness. I'm good with wiring. And the tach has a selector for 4 or 6 cylinders. The distributor and carb I plan on picking up with the exhaust parts. The guy had a cracked block so he's parting the thing out. I should be able to get the stuff cheap.

 

[Alpheus]

Re: i think my 3.0 is blown. can i go to a 5.7?

http://www.amarket.com/im184.htm

If i'm not mistaken that is all I need to change. Maybe I'm missing something...

I plan on using my old alt and hopefully the starter. The starter is almost new and hopefully I can figure out a way to mount it to the 4.3L. If not I could just sell it. I know i can use my old wire harness. I'm good with wiring. And the tach has a selector for 4 or 6 cylinders. The distributor and carb I plan on picking up with the exhaust parts. The guy had a cracked block so he's parting the thing out. I should be able to get the stuff cheap.

Well you are on your way. Good luck...

 

[alilley]

Re: i think my 3.0 is blown. can i go to a 5.7?

i am kind of on the same track with the 5.7 thing as i already either have most of the parts or have acess to most of them is why i am leaning that direction i checked e bay for a new/reman 3.0 and they are looking any where from 2000 on the bottom end to 4500 on the top end. i figure by using the stuff that i already have and what i could get the exhaust manifold,coupler, and all the parts the guy took off the marine engine for i would still come out ahead. but i dont know what would be kneeded from the risers back to the out drive for the exhaust. that is where i am totally lost at

i figure that i could use the altanator that i currently have as it looks to bolt the same as a common gm auto one. as far as the starter i dont know for sure till i got under it to loook at how it bolts on. if were to just bolt up the i would just reuse that one but that brings up a few more questions

what is really the differance between marine and auto in the following parts-
carb distrubator altanator starter fuel pump

now on the carb i did notice that there is a plastic/rubber line that runs from the top part of the carb back down to the fuel pump that is not on auto carbs. what is that used for/why is there?? is that the only differance between marine and auto carb/fuel pump??

 

[LAC_STS]

Re: i think my 3.0 is blown. can i go to a 5.7?

A marine carb is sealed to not vent any excess fuel into the bilge and the jets, springs, rods, and acc pump are different. Auto carbs vent excess fuel out of them. On vacuum secondary carbs the weight of the secondary air butterflies are different.

On the electrics (alt, starter, and dist) they are designed not too throw sparks.

So if you dont use marine you have a possibility for an explosion.

Alot of auto dist's use a vacuum advance. Almost (if not all) marine distributors and carbs do not have vacuum advance. Its mechanical.

 

[cpt ron jc]

Re: i think my 3.0 is blown. can i go to a 5.7?

i do not think it is a good idea,i have a 21 ft cuddy with a 4.3,i was thinking of the same ,they tell me its best to stay with my 4.3 its just easier to stay with the same block,i am buying a 4.3 long block ,check out RAPIDO MARINE ON THE WEB,their out of fla,mine will be 1400 to my door,then i will switch all of my tin to the new block,whatever i think is junk i will replace,also there are many marine engine co.you can check out e bay has many,its the shipping you have to watch out for,some offer,blocks with oil pan and risers for around,2100,i think rapido has the best deal check it out,you could try a 4.3,i think its a better option then 5,7 way to much balance and wt issue are only a few of what your getting into,as far as the engine goes i would get a MARINE ENGINE way better choice,i looked into this also,it will end up costing around the same by the time i was finished,with the whole project.

 

[alilley]

Re: i think my 3.0 is blown. can i go to a 5.7?

i have the v8 available all that i would need to do is change the cam to one set up for marine/truck,rv application. i can get the exhaist manifolds, risers and prob marine carb, and the coupler that all came off of a 5.7for like next to nothing ( the guy already owes me some $$$ any what). that is why i was looking in to the v8 swap. the added power is just a plus. the 3.0 has enought power to do what i want to already. the only reason why i am having to change it is cuz of getting water into the oil. at first i was thinking it could be a head gasket but with it having the crack on the out side of the block (it is about the length of the entire block soome one didnt winterize it at all i think)that even after atttempting to j b welt it it is still leaking.

as far as expence, i could have the v8 ready for water as long as my marine starter and altanator will bolt up, and a distrubator that i have will work (it is auto h e i unit) i might have less then 200 in it plus machine work for the bore job and last time i checked that was only like 150. as i mentioned i can get all the marine parts off that other motor for prob less then 100 only thing is i do not know how the exhaust goes from the end of the risers to the out drive what would be needed there??

i would go a head and just go back the to 3.0 if i could find one, or even just the block of one and swap all my parts over but that is even being tricky to do for even near the same cost that i can do a v8 for