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OMC 351W to Bravo 3?

R

Rixram

New member
Hi all.

I just acquired a free Bayliner 2755. It has the 351w in it, which I understand is about a 255hp engine. This project is for personal challenge and a labor of love. Cost is a factor, and time is about a 18 month plan.

The boat had a OMC Cobra drive on it, which was stolen off of the boat. I haven't ever dealt with OMC anything before. I am familiar with 351s, but only in automotive applications.

Now, all that being said, I have a Bravo III in my basement that I picked up "for future use" a while back. Is there any way to mate a B3 to a 351w?
I do have the full Bravo transom shield assembly.
I just can't find if there is an adapter plate to couple the engine to it.

Relevant information: the condition of the engine is unknown. On removal from the boat, the engine health will be assessed. If the engine is deemed too poor of poor condition, a SBC will be installed, rendering the question moot.
But, given my fondness for the 351 and Bravo IIIs, I'd like to see if there is a reasonable way to have both. No, I am not new to boating. I have had 7 previous boats over the last 24 years.
And I'm not trolling anyone.

Note: yes, I am aware that SEI has an adapter to make the Alpha-clone bolt up. However, that mod doesn't appear to work with a Bravo-anything.

Thanks for reading and providing helpful answers.
Please; no snarky responses. Thanks.
 
There are some complexities here, one being I don't think any Ford engine was ever used with a Bravo drive system, so no idea if it would mate up with the coupler/flywheel. If the OMC Cobra transom mount is in good shape there is another option, convert that to a Volvo SX system by changing the pivot housing, and a few other mods that have to be done, like adding a raw water pump (possible because Volvo Penta did use the 5.8 Ford engine). So sell off the Bravo, and get the needed Volvo parts for the conversion, leaving most of the OMC transom mount in place. If the engine is installed and doesn't need to be removed for any reason, and the transom mount is in good shape, this is the easiest conversion. If you want to use the Bravo drive, I think you will have to pull the engine, transom mount and go with all GM/Merc components. If it were me, I'd just convert it to Volvo if everything else is in good shape.
 
That is good advice.
The extenuating circumstances of this boat are that I need to pull the engine to replace the fuel tank.
It would be foolish of me to think a 31 year old tank was okay to use. So the engine needs to come out, anyway.
As for the transom, it is probably a good idea to rebuild it, too.

I have wanted a 2755 for 20 years. So being that is was free, it is worth the work. I get to rebuild it to be the way I want it to be.

I'm not crazy: I'm just a boater. Well, I guess that makes me crazy...
 
agreed replacing the tank is a good idea, as is checking the transom itself to see if it needs to be redone. Before pulling the engine I might do a compression test, check for water in the oil, etc to see if you want to keep it and use it in your re-fit of the boat, if so then keeping the OMC transom mount and converting the drive to Volvo makes sense, because it saves a lot of cash. The Bravo drive is probably worth as much as a Volvo SX, so close to equal exchange there, and I have run a Cobra in the salt for 15+ years and I can tell you the Cobra transom mounts hold up well better than Merc and so do the Volvo mounts as they are nearly the same as the Cobra. Going all GM/Merc means buying an engine most likely, and a complete transom mount. Price it out both ways and see what makes sense. If you want a dual prop drive you can get a Volvo SX/DP as well just more expensive.
Salt water use? was the engine raw water cooled? These things matter too, if so you have to figure how much life a raw water cooled engine used in salt has in it.
 
I have had a VP DP before, on my '99 Four Winns 258 Vista. It was an absolute joy to helm that boat.
Are you saying the VP DP would bolt up to the OMC transom hardware?

Yes, I know I need to test this engine for compression, etc. As it hasn't run in 5 years, my hopes are very low. If it does pass muster, I'll be pleasantly surprised.
As-is, the engine was used in salt water, no closed.cooling.
Oh, and I am in salt water here.

Do you have a good recommendation for finding a decent, used, DP?
 
Yes you can convert an OMC Cobra to a Volvo sx google Cobra to Volvo SC conversion, this was actually advertised by VP some years back. The parts can be bought used from eBay and other retailers.
 
4.3 new cyl heads installed.jpgHowever, I just noticed that you said you have the whole Bravo transom mount. So if that's the case, carefully evaluate the condition of the old 5.8 Ford. With raw water cooling in salt water, you have to wonder how close the cyl heads are to rust though. If this engine is questionable then your best bet is to go with a 377 or 383 small block-4bbl Carb either Edelbrock or Holley with closed cooling for salt water use. If you have all the other needed Bravo stuff this will make a good power package for that boat.

As an example, on my boat I have an original 1988 4.3 raw water cooled, used in salt water for close to 20 years now. Each year when winterized it was flushed and filled up with the best marine/no tox antifreeze I could find. I had an overheat in 2013, it ran fine after that for 3 more seasons and blew both head gaskets at the end of the third. Water in one cyl but not enough to hydrolock it. I took it apart and the block and heads looked OK. I had the heads magnafluxed and the machine shop found cracks in 2 cyls and they also felt that the cooling passages were getting eroded and would not seal after being re-surfaced. Also when you see that happening a risk is that cast iron is getting thin behind the valve seats and can rust through and cause a hydrolock. So I replaced the heads with reman 4.3 heads and put it back together. Three years later still running well. So be careful with old raw water cooled in salt engines. The heads tend to rust through sooner than the blocks. Next engine will have closed cooling from the start for sure. 4.3 starboard cyl head removal.JPG
Bottom pic is cyl head removal, top pic is reman heads installed. Both the GM and Ford marine engines are old school engines, simple and easy to take apart. To get the head bolts out I had to use a 1/2" drive impact gun, to my surprise I did not break one bolt. Due to corrosion I replaced all the head bolts with ARP bolts. For gaskets I used Fel/Pro marine head gaskets.
 
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And that is what I've been considering.
If the 351w is unhealthy, and as I said, I see that as a very real possibility, just go with a SBC. I don't think I mentioned CCS, but it'd definitely be added. Partly for longevity, and partly for heating hit water while voyaging.
I have to take a closer look at it, but I suspect that the carb may bolt over.

I'd attach a photo, but cannot seem to figure out how.
 

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Okay, apparently I figured out how to attach photos.
Looking at the carb in the 2nd pic, does something look funky about it to you?
Maybe I am.used to SBC carbs, but the overflows/spray ports, I thought, were on street carbs, not marine.
Again, I'm not used to seeing marine Ford engines, so it is probably my current lack.of familiarity with them.
 
I think the biggest problem will be the bell housing. I don't think that Mercruiser made a Ford version of the Bravo bell housing. Therefore you won't have any rear mount for the engine. IF I'm wrong then you're golden and you need only the Ford flavor mercruiser coupler (from an 888). You might find that the flat type Bravo coupler will fit the ford flywheel.
 
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No that looks like a Holley marine carb, the J tubes tell you that. The rest of the engine does not look promising to me. Manifold is missing on one side, the other one looks clogged up in the cooling passages. Exhaust elbows taken off like that suggest overheating issues. In the salt you have to change the exhaust approx every 5-7 years. Those look original!
I'd pull the spark plugs, spray penetrating oil and let it soak in. Then see if its seized or not, before buying any parts to get it running.
 
o2batsea said:
Transom hole for Cobra and Bravo is the same
Click to expand...

Now THAT is an awesome piece of news to offset what I found out earlier.
I found out from one of the boat yard assistants that apparently, someone was tinkering with this engine a couole of years ago.
They got it running: hooray!
And they had it runaway and it fragged: boo!!
I'll check to see if any parts are salvageable, and sell those off.

I had figured a 10% chance of this engine being okay. The 90% won out.
Looks like it's time for a SBC. Probably a 6.2L.
I knew this thing was going to be a mess. So far it is meeting expectations, so no disappointment.
But I did just get it tarped for winter. Shoveled piles of leaves out of it, too.
Going to demo the cabin and start that rebuild.

While I love the 351w, parts for the 5.7/6.2 are just plain easier to get.
 
I think a small block will just barely be able to push this thing. Really you should be considering a big block. It's a big bleach bottle of a hull loaded up with creature comforts (weight). It's borderline needing twin engines but Bayliner was targeting the weekend cockpit cruiser with this model, so speed and maneuvering weren't really what buyers were looking for.
 
o2batsea said:
I think a small block will just barely be able to push this thing. Really you should be considering a big block. It's a big bleach bottle of a hull loaded up with creature comforts (weight). It's borderline needing twin engines but Bayliner was targeting the weekend cockpit cruiser with this model, so speed and maneuvering weren't really what buyers were looking for.
Click to expand...

Hi o2,
I have been lurking on these message boards for a while. Only recently made an account.
I have gathered that you are the "Cam guy" here. Please correct if wrong.

I understand what you stated above. The boat, as designed with a 255hp small block Windsor could cruise in mid-20s, and max in low 30s.
Understand that I don't seek any faster than that, anyway. But I am definitely upgrading from a single prop to dual props via B3. And I want to ensure ample power for swinging those wheels.

Cruising angle of the boat will be improved by shifting the water tank out if the dense stern, and moved to the bow. Probably try to see what else I can shift forward, even if only a foot or two (like batteries).

Continuing on, what do you, as said Cam Guy, recommend for getting a 5.7L to 300+hp? I know TQ would be better if I moved to the bored/stroked 6.2L, but I want to calculate build cost vs effectivity for each 350, 377, 383. The dry weight of the boat is 5,200# dry, as-is. For towing purposes, I prefer to avoid the weight of a 7.4L.

For starters, let's presume I keep that Holley that is on the existing defunct (apparently) 5.8L.

Mods: i understand that this thread may need to be relocated, based on the OMC 5.8 no longer being a consideration.
 
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louc said:
No that looks like a Holley marine carb, the J tubes tell you that. The rest of the engine does not look promising to me. Manifold is missing on one side, the other one looks clogged up in the cooling passages. Exhaust elbows taken off like that suggest overheating issues. In the salt you have to change the exhaust approx every 5-7 years. Those look original!
I'd pull the spark plugs, spray penetrating oil and let it soak in. Then see if its seized or not, before buying any parts to get it running.
Click to expand...

Hi Louc (Locutus??).
Since I found out a few hours ago that someone apparently detonated the innards of this 5.8, I need to see what can be utilized from it for a SBC.
I an used to Carter, Roch, and Q-jet carbs. Which figures, considering that every sterndrive boat I have had (5 sterndrives of my now-8 boat history) have been Mercruisers. The other 3: VP w/FI, V-drive, and 1 OB.

So this is the first Holley I have had. I know the name, of course. But not the strengths/weaknesses of them. Care to share some of your knowledge? Enlighten a hopeless addict of abandoned boats, perhaps?
 
I suggest that you start looking around for a good used running take out that you can drop in with the least amount of fuss. There's nothing to save on that old ford. The carb is suspect since it's clearly been sitting for ages. Dump all of it. Believe me, been thru this several times.
I found my most recent engine and B3 on Craigslist. The entire 7.4 efi and b3 drive cost me 3500. I dropped another couple thou on parts and a service on the drive. It had only a few hundred hours on it and when I pulled the heads off the cylinders are like new still. I'm just sayin that even a good used engine needs a thorough going over to include all new gaskets and seals. I also replaced the manifolds.
A realistic figure for repower with used will be somewhere between 5 and 10 thousand. If you're really that committed to this project, think about the big picture.
Maybe you should get this one that's running and driving:
https://washingtondc.craigslist.org/doc/boa/d/washington-1993-bayliner-ciera/7254036669.html
 
o2batsea said:
I suggest that you start looking around for a good used running take out that you can drop in with the least amount of fuss. There's nothing to save on that old ford. The carb is suspect since it's clearly been sitting for ages. Dump all of it. Believe me, been thru this several times.
I found my most recent engine and B3 on Craigslist. The entire 7.4 efi and b3 drive cost me 3500. I dropped another couple thou on parts and a service on the drive. It had only a few hundred hours on it and when I pulled the heads off the cylinders are like new still. I'm just sayin that even a good used engine needs a thorough going over to include all new gaskets and seals. I also replaced the manifolds.
A realistic figure for repower with used will be somewhere between 5 and 10 thousand. If you're really that committed to this project, think about the big picture.
Maybe you should get this one that's running and driving:
https://washingtondc.craigslist.org/doc/boa/d/washington-1993-bayliner-ciera/7254036669.html
Click to expand...
That one looks nice, there in lies the rub; it *looks* good.
We both know the fuel tank needs replacement, the transom likely needs a rebuild. For a boat that clean, to be priced that low, there is something really wrong with it. Particularly in the current market.

I am okay with spending the right money on it. I sm not one of those people willing to buy a crate motor. I have a drive already. If I spend 5-10k over a couple of years to bring this one back, and know darn well that it is built right, and not constantly concerned about what the PO hid/messed up.
And I've wanted to build a boat my way, and I have loved the 2755 for a long time.
 
OK, well, hope you get it going soon! Do you have the Bravo Y pipe too? That'll help a LOT. The rest of your installation should be pretty much a straight drop in.
 
Looks like the ECM is included too. I think that's your power right there. Def wanna check out the overall health of that, but I would certainly go and see what it looks like in person. Sometimes people just want more oomph and take out perfectly good low-hour engine in favor of a big block.
 
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o2batsea said:
Looks like the ECM is included too. I think that's your power right there. Def wanna check out the overall health of that, but I would certainly go and see what it looks like in person. Sometimes people just want more oomph and take out perfectly good low-hour engine in favor of a big block.
Click to expand...

I sent in a message this morning, as soon as I saw your post. I do believe that'd work nicely, as I do want a full closed cooling system, too.
 
While Holleys have rather limited use in the marine market from the OEMs, they sell a full line of Marine carbs. If you were looking for a new marine carb its basically either Holley, or Edelbrock and the Edelbrock is basically a slightly modernized Carter design from the 60s. Holleys at least marine ones are the same old Holley design. Both have their fans, I think you see more Edelbrocks being packaged with new engine repowers from engine sellers. Holley dominates in the classic car and hot rod biz though. Personally I prefer a Quadrajet, if you can get a good core, problem is they were last made 30 years ago while the other 2 you can buy new.
 
Cruising angle of the boat will be improved by shifting the water tank out if the dense stern, and moved to the bow. Probably try to see what else I can shift forward, even if only a foot or two (like batteries).
Click to expand...

You may want to do some sea trials before moving weight forward. There can be unwanted effects from bow forward weight. Generally speaking you want the weight aft where the hydrodynamic wedge is lifting the hull up out of the water. You don't want to have that certain, sinking feeling. From the Bravo 3 installation manual:


It has been brought to our attention that some boats (predominantly deep-Vee heavy boats)
will roll up on their side under certain, specific, operating conditions. The roll can be either
to port or starboard and may be experienced while moving straight ahead, or while making
a turn. The roll occurs most frequently at or near maximum speed, with the sterndrive unit
trimmed at or near full trim-in. While the boat will not roll completely over, the roll may be
sufficient to unseat the operator or passengers, and thereby create an unsafe situation.
The roll is caused by stern-lift created from excessive sterndrive unit trim-in. Under these
extreme stern-lift / bow-down conditions instability can be created which may cause the boat
to roll. Weight distribution to the stern can reduce stern-lift and, in some circumstances, help
to control the condition. Weight distribution in the bow, port or starboard, may worsen the
condition.
The Trim-In Limit Pin Insert reduces stern-lift by preventing the sterndrive unit from reaching
the last few degrees of full trim under. While this device should reduce the rolling tendency,
it may not eliminate the tendency entirely. The need for this Trim-In Limit Pin, and its effec-
tiveness, can only be determined through boat testing and is ultimately the responsibility of
the boat manufacturer.
Click to expand...

 
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o2,
I totally get where it is you are coming from.
I will add these two counterpoints for discussion:
1] We have trim tabs to lift the stern up, and force the bow down due to weight in the stern.
2] And this is really an extension of #1. I had, as boat #4, a 1999 Four Winns 258 Vista. It had a Volvo Penta DP, the water tank in the bow, and the hull extended out past the transom, to the edge of the swim step. It had that extra bouyancy in the stern, and the bow was heavier.
I never needed the trim tabs on that boat, with the exception of when taking strong wind on the beam, once. When I say I never used them (save the noted point), I mean that literally.
On sea trials, I revved the engine to 3,000 rpms, because pretty much every boat we know is "on the hump" at 3k rpm, so still at or under 10 knots, but the engine is starting to work hard. I had it there to check oil pressure and engine temp. I'd been watching the gauges for about 15 seconds when my (then) MIL tapped me on the shoulder, and pointed ahead. We weren't on the hump, but were clipping along at 19-20 knots, instead. I've never had another boat before or after do that.

You may be asking yourself, "Self", as you likely call yourself, "Self, why doesn't he just get another Four Winns VP?"
Glad you asked. It was too small, length-wise. The 2755 is 2' longer, and that makes it ideal for me.

But, yes, trim tabs are the #1 reason why we should know that having all that weight in the @ss is not out of ideal marine engineering, but of manufacturing convenience. So taking 28 gallons (~230#) of water out of the ass and moving it forward will result in a 450# shift in weight forward.

I'd love to discuss this further.
 
Shift MIL forward. Ha ha ha.

The install manual quotation does not refer to the trim tabs, but rather the drive trim (rams). Trim tabs are a whole other discussion.
Where the weight is best located in the boat depends on a lot of things, so what works for my boat may not work for yours. You use the boat frequently enough, you'll figure out what's the best.
I doubt very much that you'll experience the sheer terror of having the boat roll onto its side at full cry ( can you imagine having that happen on a boat with a tower? ).
 
351w to SBC/B3

o2batsea said:
Shift MIL forward. Ha ha ha.

The install manual quotation does not refer to the trim tabs, but rather the drive trim (rams). Trim tabs are a whole other discussion.
Where the weight is best located in the boat depends on a lot of things, so what works for my boat may not work for yours. You use the boat frequently enough, you'll figure out what's the best.
I doubt very much that you'll experience the sheer terror of having the boat roll onto its side at full cry ( can you imagine having that happen on a boat with a tower? ).
Click to expand...

I am not terribly concerned with severe rolls. If things are that rough, I'll stay at anchor, or better yet, home. I did my years at sea enough to know that Sea State 4 is my limit.
Got caught up in some bad weather a decade ago (pleasure craft, not military), and had to trudge through about 3 hours of it at about 8 knots. This was in the afore mentioned Four Winns 258. Boat did well. I had a "Yeah, that was fun, but not enough for twice" times.
 
To clarify, Mercruiser's reference to rolling is not related to how rough the waters are. This effect can happen in flat calm. In fact it might even be more likely in calm seas rather than disturbed as the effect depends on the right conditions of speed, too much trim in, and weight distribution. The effect is sudden, and there is nothing that can be done to recover or minimize once it has entered this condition. It would be the same as driving your car on the highway and suddenly have it flip onto its side without warning at 80 mph. Happens before you know it.
The remedy is to be sure that your trim limit is properly set to avoid too much stern lift, move some weight aft and keep your speed down.
This is the same effect that killed a few people using "Texas Flats" style boats that were outboard powered.
 
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