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3.0 is shot, can i swap it out for a 5.0/5.7?

A

alilley

Member
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 method, 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. i am also noticing that the spot where the rubber hose that connect to the top of the valve cover for crank case ventalation does have what i feel to be a pretty good amount of air coming out of it. 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
 
you would need to change the drive gears, you would need the room in the engine bay, and the stringers set up for the motor mounts then you need everything behind the motor.

Cheapest way for you is ebay look for a fresh water motor make doesn;t matter but merc would be nice. Different make then you will need to use the mani and the riser off your setup.
 
could i just run a lot mor agressive prop to instead of changing gears? is there a differance in the gears that are in the alpha 1 behind a v8?
 
What does the Coast Guard placard state the max. HP can be? That's your limit. Replace the 3.0L w/a good used one and be done w/it; you're geting yourself into a deeper money pit.
 
My feeling is that you have gotten your use out of it. Best cut your losses now. Even if you find an engine and install it, you'll still have a boat that's only worth a thousand bucks. Your time is certainly worth something as well. You have to think that your labor is at least $60 an hour. How many hours do you think it will take to do a swap? Several long weekends worth for sure. Do you really want to invest that much time?
The only thing you can do is put an ad on craigslist for it and see if anyone bites. Maybe you can get a few hundred for the drive, and maybe parts off the engine are worth something. It's done, toast, put a fork in it and move on.
 
i am not putting it up for sale as we have only had it for a few months. i am not concerned with the amount of time that i put into it as i really enjoy working on that kind of stuff. on top of that i bought it knowing that it had a cracked block and was taking a chance on that. well tht bit me. so my options are to either repower it with a nother 3.0 or upgrade it to a 4.3, 5.0, or a 5.7. dad just reminded me that he has a running 4.3 out of an vanand that we could put that inany thoughts there??
 
I pulled a 3.0 out of my Bayliner 1851 and replaced it with a 185HP V6. I replaced the 1.98 drive with a 1.81
For a V8, you need the 1.5 or 1.47 ratio for 2 reasons
1.to handle the power and
2. to spin the impeller fast enough for V8 cooling
cheaptrick007.jpg
 
Budget $2K minimum if you have a good running 4.3. More like $2500k if you want power steering and your 3.0 doesn't have it.

$1000 will be required for new Ypipe and manifolds.
another $500 to $1000 or so for all the marine externals from eBay or whatever - ign, carb, intake, water pump, bracketry

the rest of the work was fabricating mounts, and trying to figure out how to get the tach set and where to mount the shift mechanism....that was $200 just for the update interrupt shift assembly to mount. lots of surprise expenses... like any project - the deeper you get, the more you want things to be right... and used junk doesn't cut it once you have the hull gutted.. the deeper you go, the more you find that you want to improve.
I made sure my hull was offered with a V6, but that turned out to be a non-issue for insurance.

If my boat wasn't absolutely mint and something I know I can use long term... wouldn't have done it.
 
Hystat:

Nice boat. I see the exhaust blower doesn't have a vent hose dropping into the bottom of the bilge. I don't know about Canada but the U.S. Coast Guard requires that fumes be sucked directly from the bottom of the bilge. I used a coiled aluminum dryer vent hose on mine. It was easy to form it so it fit around the "Y" pipe.
 
interesting - I have some of that blower hose - will tack a piece on there..... tks.

Oh another factor to consider- Fuel Tank size...

the Bayliner has a 30 gal tank.

My other boat I did a 4 to V6 repower on has a 15 gallon tank.... not good with an engine quite capable of burning 7 gallons/hour at cruise...and 11 GPH for watersports and there's nowhere to put a bigger tank on it...
 
I also opened a closed fresh air inlet and attached a section of hose and routed it to the front of the carb to provide cooler combustion air while under way; hung it from the engine cover.
 
You will eventually wish you had spent the hundred bucks to drop it in the land fill. The amount of time and money you are considering to spend on what is more or less a worthless lump (NADA Guide puts its value at 450.00, so clearly you are already 550 bucks in the hole, but since it has a blown engine that value is zero) would be far better spent on something that (A) runs and (B) will be worth investing money in. Find an old Grady White or a Sea Ox or a Larsen or one of a hundred other boats of much better quality and demand than a clapped out Sunchaser.
You have the marine equivalent of a rusty old Huffy bicycle. Use it to gain experience if you insist on keeping it.

Just buy a big bilge pump and run it leaks and all, forget repowering.
 
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I would suggest just finding another 3.0 out there. Much easier and cheaper for that year of boat.

Run the boat for another 2-4 years and get some fun value for your time and money. Then, sell/trade for a boat with a V-6 or V-8 if you want/need the extra power.
 
For it to be cheap you will need a donor boat with a bad hull and good drive and motor, or you said you have a truck motor then you need mani;s and risers. 500 bucks.

Then you can transfer everything over from the donor.

Otherwise get a 140 / 3.0 drop it in and enjoy yourself. One day to pull the old motor and install the new motor, pull the drive and re-install it. Just pull the motor and leave the bell housing.
 
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 just checked here and they have one to replace the 3.0 with but it is in excessive 3000 i know i could drop the v8 in it for prob around half of that since i have all these parts currently available
 
$1500 into a V8 for a boat that's worth $450? NADA Guide sez with a 5.7 V8 boat is worth a lofty $2265. You might break even.

>What length boat? What is the horse power limit on the Coast Guard sticker?
It's a Sunchaser. These came with any Mercruiser you wanted to put in including the 7.4/454.
 
if i could find a replacement motor or even just a block that i could be done for near the same cost then i would do that in a heartbeat but evey time i turn arround and the cheapest one i found so far was 1895

as i have stated i just purchased it and dont really dont want to unload it if i do that i will wake away from boats all together
 
ok so lets set the v8 swap to the side for a little bit here. i have been doing some checking on some things and talked to a few machine shops in my area that have shed a little light on things for me and raised a few questions. to start off with i will explain what is going on.
-- getting water into the oil (looks like a thined out wendy's frosty),
-- engine block is cracked to the out side for sure,
-- motor runs up to 4000 rpm to just under wide open throtle (if i go to full then it boggs and hesitates) with norm load
-- getting blow by through the crank case vent tube
-- noticing exhaust smell when up to speed but not as noticable when at idle/nowake
-- plug wires keep falling off during ruff water as they fit loose in the cap


i was then suggested to get the head magna fluxed to make sure that it was not cracked. as that might be here i am getting water in the oil from. if that is the case then what i would do is get a rebuild kit for .030 over standard bore. weld the block back shut, have the deck planed to ensure trueness. so that would button up the bottom. then find a differant head which would be a lot easier to find then a new block

what other then the head being crack could cause the water in the oil issue?
i hae had the manifold and riser off and all appiear to be good an not cracked and many thanks again as i was not tryin g to get people fired up was just trying to go the least expensive way out to get boat back on the water
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i am trying to figure out how the water is getting into the oil. is there any other way other then a crack in the block, head, or a blown head gasket (which i know is unlikely but they do happen).?

i had put a few hours on the motor will on muffs with fresh oil. i checked it before foing out the first time and it still looked like oil. we went out 3 time that may have totaled less then 5 hours. we did both full throtle and no wake speeds. the last time we took it out we started noticing that it was cutting out which was caused by the loose plug wires. wile i was fixing that i noticed that there was somthing sprayed on the bottom side of the engine cover. coresponding to somthing being sprayed over the top of the riser, the bottom or the carb and top of the manifold. as soon as i seen it i knew it was oil, i pulled the dip stick and sure enough over full and as i described earlier it looks like a thined out frosty. pull the plug out of the valve cover (where you put the oil in at) to look inside there and sure enough foam/froth under pulg, top of the rockers and about any where it can settle. at that point we took it back to our dock and tied her off. that is where she has sat for since monday. i will be pulling it out of the water once i get back in on saturday
 
Know of another way for a auto motor to get water in the oil. This is a auto engine essentially. You already know it's cracked the block, you thought it was only external. Now you know it's internal also.

Someone did not winterize it correctly.

I saw today a 3.0 on ebay. Always see them. Your lucky you have only fresh water by you get a local 3.0 and junk the block you have.

Does not matter the make cause you can always switch over the riser and mani if you get any other make besides the one you have, or get a little creative with the rubber hose that connects to the exhaust tube.

When you have the motor out look for the flapper / shutter, and then get a manual or d/l one for free.

Ask here really nice and maybe someone will email you one. I know a few nice people here who have them, they don't want money for the d/l just a thank you will do.

So to be clear, you need a 3.0 / 140 i did the exact same thing your doing, i changed out my 2.5 for a 3.0 / 140.

You would do well to get a fresh water used one, with good compression, if they don;t allow you to check compression do not buy it.

Don't toss the one you have, not yet you may need stuff off it. Keep your chin up all is not lost, you can recover from this, and don't kick yourself anymore chit happens.

May the force be with you !
 
chiefalen thank you i really need a little encourgement right now on this deal as it is quite frustrating.

will a 2.5 bolt right up??? i cought wind of one today that came out of a small truck only thing is it is fuel injeclted and mine is not. i9 was thinking about grabing it and switching it over using all my marine parts on it but was not sure if it would bolt up. how much power would i loose??with going to the smaller motor would i still be able to pull a tube/skier come next year?

where is the shutter/flapper you are talking about?i am assuming that it is there to keep water from going back up the exhaust when the wake hits the back of the boat?? is that correct

if any one know where i can either purchase a service manual or even down load it that would be a great help as well.

what are the odds of the head being cracked as well?? what i am hoping for here/thinking here is if the block took the blow where i know it did why wouldnt the head take one as well and that is how i am getting water in the oil? i checked with a machine shop and they can magna flux it for 40$. if the head comes back clean then i know the block is total and then i am back to looking for a used 3.0 block again

once again many thanks as it has helped keep me along the strait and narrow --as far as max power for the boat i will have to double check once i get back to the house
 
one more thing i am confused on. will my parts bold up to a volvo/omc or does it have to be mercruiser? if so that would greatly widel searches? i seen an add for somthing on e bay that stated it was for mercruiser/hyster?? is that the same motor that is in fork lifts??? what elese can my parts swap over to??
 
When you go looking for an engine the best approach is to try to match your existing engine as best you can. Same year, same size, etc. The fact that it might be a car (or truck) engine does not matter all that much for fresh water operation.
The marinizing parts; intake, exhaust, carb, fuel pump, flywheel, bellhousing and water pump, will better bolt on to it. Really all you need is the block and head. All your parts should swap over as long as it is the same-ish. You might even put the cam from the marine engine in the new block. Boat engines are always pushing "uphill" so the marine cam will be better than a car cam.
When you finally find what you need (this season is probably a wash out) be sure to use new gaskets and clean things up as you go along. I use a water based degreaser and soak parts to get the grime off. This will make working on the engine in the future less of an ordeal since it is less messy.

Replace with new all the rubber parts...belts hoses and all the tune up paarts like cap rotor points wires and plugs. even a tired engine will feel like new again. Discard old hose clamps and if you can afford them, use AWAB clamps.
 
o2batsea quit pissing on this guy's cheerios. he wants to fix it that's why he's here.

If the rest of the boat is in decent shape such as drive, interior, hull, everything else, your best bet is find a rebuilder and get a remanned long block for a couple thousand dollars. Some even have warranties. You can re-prop later.

Here is an example of a place in my area.

http://www.usengine.us/mercruiser.html
 
can any one teel me if i have to have a mercruiser motor or can i use either omc, volvo, or mercruiserto replace my mercruiser 3.0. this info would be of great help when looking for my replacement
 
as the other forum members stated you must replace with the same motor or the cost goes up rapidly with many surprises.

since you have time search for a motor same as yours that works , used.

what year and size boat is this ? I suspect 18feet . 1980's.
 
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