3.7 to 4.3 swap

[achris]

Where I spend most of my time fishing is usually the sweet spot between the boat staying on plane and dropping off plane, any faster and the sea will beat the snot out of me. Where I could use more power is in the bay and rivers however when we go outside that extra weight would offset my balance of planing or not (in my opinion). I am simply looking for more reliability than the old discontinued 3.7 can give me. I have had this boat since 2008 and have never been disappointed in its performance inshore or offshore. But am tired of digging for good used parts and the feeling that I'm stuck with this motor eventually leading to the demise of my boat which I love. Just trying to get ahead of the inevitable

Nicely put.

I had exactly the same equation to balance in 1994. Loved the boat, but the engine was causing issues. Discussed with the wife (at the time) and we threw a brand new engine in. Best decision we ever made....

At the end of the day it's only you who has to justify what you do and how you do it. You have heard a lot of advice and opinions voiced here. Take all that, make a decision and go with it...

Good luck,

Chris........

 

[Scott Danforth]

there are things that can be done to improve the 3.7 reliability, however you are correct that it is not supported from a parts level very much.

from that point, any of the V engines would not have you digging and looking for "good used parts"

however that point just on the edge of dropping back into the hole vs being on-plane is the highest consumption point there is. that is where the hull loading is highest. I personally would get up on plane and then adjust the trim tabs and drive trim to adjust the angle of attack of the bow to minimize the pounding

 

[achris]

Using a 4 blade prop will help stay on plane at a lower speed too.

 

[Dubed]

there are things that can be done to improve the 3.7 reliability, however you are correct that it is not supported from a parts level very much.

from that point, any of the V engines would not have you digging and looking for "good used parts"

however that point just on the edge of dropping back into the hole vs being on-plane is the highest consumption point there is. that is where the hull loading is highest. I personally would get up on plane and then adjust the trim tabs and drive trim to adjust the angle of attack of the bow to minimize the pounding

I have done the alternator conversion, electronic ignition, eliminating the old water cool regulator and other issues. Bigger problem is not being able to find the exhaust components. Fact of the matter is, this motor is just no longer completely supported. I just spent a ton of money rebuilding it, and the block failed. It's exhausting. Kinda like my ex-wife. Still love her, we've had a lot of great times together, but in the end it was all bad.
The boat doesn't have trim tabs, never needed them. Perhaps I will after the conversion. Point I was trying to make is the speed I need a lot is between getting beat up by 3' seas or dropping off plane and adding weight in ass may not be helpful.
Hopefully get the ole 190 back in the boat soon and she gives me plenty of love till I find all I to to make the swap!

 

[Blorton]

While we’re on the subject - for a lake boat, what’s the reason for not wanting an aluminum block?

 

[Rick Stephens]

While we’re on the subject - for a lake boat, what’s the reason for not wanting an aluminum block?

Not much to do with lake or sea water. The problem is aluminum block and steel heads. Different expansion rates. Also the funky water pump.

 

[Blorton]

Thanks. I keep hearing people talk about the negative effects of going up to a v8 due to added weight and was wondering why folks aren't going with one of the all aluminum crate engines that GM sells. (Yes, I'm a Corvette fan.)

It probably doesn't make much sense in current days, but there was a time when you could get nice new long blocks from the General for relative peanuts. I know marine duty cycles are a very different animal, but the LSx platform is very reliable and I'd run one in a hearbeat for a lake boat.

 

[nola mike]

Thanks. I keep hearing people talk about the negative effects of going up to a v8 due to added weight and was wondering why folks aren't going with one of the all aluminum crate engines that GM sells. (Yes, I'm a Corvette fan.)

It probably doesn't make much sense in current days, but there was a time when you could get nice new long blocks from the General for relative peanuts. I know marine duty cycles are a very different animal, but the LSx platform is very reliable and I'd run one in a hearbeat for a lake boat.

Because they aren't made for a marine application. Accessories, brackets, exhaust, couplers, ignition, etc etc not available.

Merc is making aluminum blocks again for their engines.

 

[jimmbo]

Thanks. I keep hearing people talk about the negative effects of going up to a v8 due to added weight

The extra power/torque of the V8 more than covers the extra few pounds. On the Brighter Side, you could convince the Wife and Kids that they hinder the Boat's Performance, and should remain ashore. Girlfriends and Mistresses, need not be sent ashore.
When I was buying my I/O, it was offered with a couple of 5 liter engines. One was 220hp with carb, and the other was 260hp with FI. For some reason, my Dealer had gotten one boat with a carbed 5.7, also 260hp(it wasn't an option, maybe they didn't have a 5 liter FI handy). I grabbed that one. A couple of years later, I was at the lake, and one of the 260hp FI versions of the boat was there. We had a comparison, and the difference was Night and Day on acceleration and even top speed.
Much to the annoyance of some people on this site, I will always tell people to get the biggest engine they can, even though they may not need it, cause you never know, and it also makes the Boat more Marketable, if at a later date, they want to sell it

 

[Scott Danforth]

Thanks. I keep hearing people talk about the negative effects of going up to a v8 due to added weight and was wondering why folks aren't going with one of the all aluminum crate engines that GM sells. (Yes, I'm a Corvette fan.)

It probably doesn't make much sense in current days, but there was a time when you could get nice new long blocks from the General for relative peanuts. I know marine duty cycles are a very different animal, but the LSx platform is very reliable and I'd run one in a hearbeat for a lake boat.

the Seven Marine outboards were either an LSA or LS9 engine (depending on power output)

The Volvo Penta motors are LSx variants

one of the things that I recommend on a 470 is to buy an aluminum edelbrock Ford FE head (429/460) and drill the one hole and get rid of the iron head on the motor that Mercruiser put on it.

We had a comparison, and the difference was Night and Day on acceleration and even top speed.
Much to the annoyance of some people on this site, I will always tell people to get the biggest engine they can, even though they may not need it, cause you never know, and it also makes the Boat more Marketable, if at a later date, they want to sell it

There is still no replacement for pure displacement

 

[Blorton]

the Seven Marine outboards were either an LSA or LS9 engine (depending on power output)

The Volvo Penta motors are LSx variants

Incoming “Converting my 4.3 to Penta thread…”.

In all seriousness, I am expecting enough hours on this boat, I should be looking into diesel.

 

[Dubed]

So you guys hijacked my thread and turned it into a "mine is bigger than yours" thread.
I was looking for advice upgrading from the 3.7. I think a 4.3 would be perfect but certainly have not ruled out the 5.7. I think the outcome of this decision will be dictated by the donor boat. I will leave all my options open till I find everything I need.
I thank all of you for your help and experience.

 

[Scott Danforth]

Incoming “Converting my 4.3 to Penta thread…”.

In all seriousness, I am expecting enough hours on this boat, I should be looking into diesel.

The VAG 4.2 liter ans 3.0 liter marine diesels are great engines

So you guys hijacked my thread and turned it into a "mine is bigger than yours" thread.
I was looking for advice upgrading from the 3.7. I think a 4.3 would be perfect but certainly have not ruled out the 5.7. I think the outcome of this decision will be dictated by the donor boat. I will leave all my options open till I find everything I need.
I thank all of you for your help and experience.

no intent on hijacking, however I guess it did happen

 

[Dubed]

The VAG 4.2 liter ans 3.0 liter marine diesels are great engines


no intent on hijacking, however I guess it did happen

Hahaha! No problems. I just hope to return to this thread when I find a good donor boat and continue with the tons of questions I'm sure I'll have!

 

[Dubed]

the Seven Marine outboards were either an LSA or LS9 engine (depending on power output)

The Volvo Penta motors are LSx variants

one of the things that I recommend on a 470 is to buy an aluminum edelbrock Ford FE head (429/460) and drill the one hole and get rid of the iron head on the motor that Mercruiser put on it.


There is still no replacement for pure displacement

What benefits would there be from installing that aluminum head on the 3.7? Just similar expansion/contraction and less weight? Or is there a performance value beyond that?

 

[achris]

Incoming “Converting my 4.3 to Penta thread…”.

In all seriousness, I am expecting enough hours on this boat, I should be looking into diesel.

If you're concerned about weight in the stern, you won't be looking into diesel for very long. And even if you ignore the extra mass without any bonus power, the $pendies will knock your socks off. I took the exact route you're taking in 1994 and then again in 2006. Diesel's nice, but heavy in the boat and on your pocket. (Like double the $$$ for the same power as a petrol engine)...

Chris...

 

[Scott Danforth]

What benefits would there be from installing that aluminum head on the 3.7? Just similar expansion/contraction and less weight? Or is there a performance value beyond that?

same expansion/contraction rates to keep the head gasket from spitting. would also install a bore stabilizing spider to keep the open deck from flopping around

 

[Dubed]

Found a good donor motor and stripped down to bare block. Machine shop started the machine work then the parts will be swapped from the rebuilt motor.

Next time I take this motor out of the boat, it will not be going back in!