1988 180 3.7L (470) Mercruiser Dual Exhaust????

Hello I have a 1988 WellCraft 180 with the 3.7 Mercruiser and I really want to get more power out of it. I love this motor...very strong..I have had this boat for almost 5 years now and have had to do nothing but routine maintenance but instead of getting a new boat, I would like to try to get more power out of mine. One guy at work told me that just putting dual exhaust on it would give it a dramatic increase in power. This sounds great, but is it even possible? I called my exhaust guy and he said that the water might run through the manifold. Does anyone know of what I can do? Thanks for all the help...

Re: 3.7L (470) Mercruiser Dual Exhaust????

The biggest bang for the buck would be a cam change and a recalibrated carb. The heads can flow a lot more than they are used for now.

Other than that there is most likely NOTHING you can do to make more power. the exhaust is no prohibative so it is not causing any real power loss. Your friend is wrong on that one..........Anyway there is no such thing available for that motor that I am aware of.

Do you know what your motor is??

It is a Mercury custom aluminium block, Sleeved with a ford big block head. Super long push rods, huge pistons, and a wimpy gm style points ignition.

It was specifically designed as a small package large displacement 4 cylinder with enough power to put it into larger boats as a low cost alturnative to a V6/V8.

It has many week points to it and if you were to increase the power without addressing those points the motor will not survive long!!

Better to either rplace the motor with a V6 or V8 or a more powerful different boat.

JMHO

Re: 3.7L (470) Mercruiser Dual Exhaust????

Thank you Kghost for your help. I do realize that the 3.7 is a very unique motor. I did know that it is a aluminum block and Ford head. It is my understanding that it is half of a 460 big block. I am also going to convert the points to electronic ignition which will cost me about $150 just in parts from my local boat shop. What pitch on my prop will make me have a better take off?? I have no idea what I'm running now, but mainly I guess I just want more initial power...it seams that would be my goal here. Other than this....I am a big fan of my motor. It runs great. I have had no problems at all...other than the points went out in late summer of 09. I am what I call the second owner and the guy before me was a lawyer going through divorce and he had it for 17 years. The original owner won it in a raffle drawing and he was the lawyers best friend. According to the lawyer he never really used it. I have had this boat for almost 5 years and I have had no problems with it at all other than routine maintenance. How hard would it be to switch motors and /or is it more cost effective rather than just selling and buying a different boat?

Re: 3.7L (470) Mercruiser Dual Exhaust????

In my opinion if you want more, buy it!! Do not try to recreate your boat. It will cost a lot in time and energy vs upgrading. Also your boat is set up for a in line engine (motor mounts) all V6 and V8 boats have different stringer layouts (positions).

That motor is not "1/2" of a ford motor. It has a Ford head, that is it!!

The way a prop pitch works.......... most boats (17-22 ft) ( pleasure only) are designed to run a 17-21 pitch prop.

Prop pitches are typically in odd numbers. 13, 15,17,19,21,23.................

The pitch is determined by WIDE OPEN THROTTLE, Trimmed up full speed operation to reach max reccommended RPM's. Tiypically 4400 -4800 rpms (varies based on motor. (some newer boats have higher rpm max specs).

So If your boat has a 19 pitch and you are running at WOT 4600 rpms then you are exactly where you should be.

If not then you reduce your pitch one size to a 17 and that will increase your max rpms by ~ 300 rpms. It "may" also decrease your max speed (MPH) as there is a trade off. This change will also give you a better "hole shot". The boat will come out of the water faster.

There are also better props (stanless steel) that can do silimar gains but costs more $$$ without some of the losses seen with aluminium props.

The bottom line is, you have a good running boat, dependable and does what you pretty much want. If you want a better hole shot for pulling a skier or tube either lower the prop pitch or buy a prop that can do both (there are props that will change pitch with internal cams and springs).

I would leave what you have for a motor as it is and do NOTHING other than your ignition upgrade and leave well enough alone........

You want more power? buy one that has more and or the ability to be modified to make more ( a V8 boat).
inline 4's and inline 6's and even V6 motors have marine application limitations on power. If you get to a V8 motor power will only be limited by the hull design and outdrive.

Re: 3.7L (470) Mercruiser Dual Exhaust????

One guy at work told me that just putting dual exhaust on it would give it a dramatic increase in power.

Click to expand...

Ayuh,... That guy at work, don't know 'is azz, from an exhaust pipe.... That's Pure Bullship.....

Be happy with what you've got,...
Or,...
Trade up to a barge with a Bigger Motor...

Listen to what kghost and Bondo are saying! And please do not put thru-hull exaust on a 470! It will sound like cheet and I guarantee you will get water into the engine sooner or later especially #4. Also, check your exaust flapper in the exaust pipe to see if it is intact. Some guy from Texas tried the same thing with the thru-hull exaust deal and posted the outcome that I just described. He blew the engine up and was upset because it had run perfectly until that point. I asked the same questions on a few sites not so long ago. I have the same identical engine package on my boat. If you plan on keeping it, do the pertronix ignition upgrade and keep the old points on board in case something takes a crap. Did the previous owner do the aftermarket alternator kit or do you have the imfamous water cooled voltage regulator and the rectifier at crank (generator) setup? If so that is good!, If not you could have problems with overcharging or undercharging of electrical system. (boiled batteries or dead batteries not to mention performance problems such as possible weak spark situation causing hard starts, rough idle, backfire or worse. The alternator setup costs around $300-$400, The pertronix setup should cost you around $85-$95 if you can do it yourself. Believe it or not, you might cause an argument on another site trying to support these two critical upgrades by some old timers who swear by points and the original voltage regulator setup. I don't agree because the second I installed the pertronix setup I was able to attain a lower idle and overall the motor just seemed to have more power than with the points. Get a 40,000 volt coil for it as well, but don't go to high (alot of heat for a small little cap). Have the front seals on the water circulator pump ever been changed? What"s the compression like? Has the engine ever had an overheat? One last thing, If it is not there, install an overheat buzzer light and even an overheat shutdown (something to kill power to the coil or ignition so as not to blow head gasket) Overheating a 470 is bad news and can cause you alot of grief so do whatever possible to avoid it. jmho
Whether I like it or not at this point I am married to this engine system! lol ( I spent alot of money on rebuilding engine, I did all work except machine work myself and it still cost about $3600.00) Parts are getting hard to find for this particular engine system and they are not cheap! I like the economy that the engine gives but if I were to do it again, I would have gone with a carbed 4.3 litre v-6 or even a small block v-8. Don't expect too much from this motor in performance and enjoy the thing as long as you can. best of luck, Tom