400 and 440 Modifications
17 September 2018
There are still some nice 440’s out there - and - contrary to the “bigger is better” crowd - a well prepped 440 will run with most 550’s and run away from many AND - they are smoother and far more reliable ( with the exception of the 91 thru 95 550 SX reed motors ) -- AND -- not everyone has a bottomless checkbook.
IF - you have a stock 400 - or - 440 - 1976 thru 1983 - and you want to make it just a bit more “crisp” - then this is what you do. Remove the head and take it to the local machine shop and have them mill .080 from the surface. Yep - that will mill off the combustion chamber “lip” - not to worry - you CAN go as far as .120 - but - that is not needed here. Use a new OEM head gasket and re-install - making sure everything is super clean. Install a set of straighter bars to allow you to move further forward on the tray. Install an aftermarket intake grate - Jet Enterprises made the first and still the best - many people copied it - a Westcoast - Jetco - or PJS is just fine. Do NOT silicone between the grate and the ride plate. Check the prop to pump clearance and make sure it is tight - if it is not - install a new OEM prop. Quick turn steering is a great idea - and - how to do that is in the files - but - this and ride plates are personal preference - and nearly everyone has a “favorite” and most of them are wrong. Good luck. You should have “about” 180 to 190 PSI compression - make SURE. If you have a variance of 10 pounds or more - YOU HAVE ANOTHER PROBLEM - fix it first. IF - you have a 1981 thru 1983 - make SURE your choke has been removed and a primer installed - if you do not - you WILL be sorry. Very sorry. The above is ALL you should do - unless - you are prepared to go - all the way. The above will pull a 200 pounder out of the water and give most anyone a “good” ride. You should be in the 35 MPH range - but - it will take a bit to get there.
Want more - ??? That is all well and good - BUT - if you do not have the money to do it “all” - don’t start. The following mods need to be done “all together - at once” - no piecemeal.
Super Stock - Stage 2 - kickass 440 - Remove the motor and the pump and the driveshaft and install a bulkhead support plate. ( bet that sent most people running ) - Buy a dual waterline kit and install it - drilling out the brass fittings before installing - ( an option is a ½ inch single line - and that is fine ) - I recommend NOT using the stock water line - drill and install 2 new ones and cap off the old OEM line. Leave the bilge alone - it works fine. Carefully re-install the drive shaft with at least new seals - and preferably new bearings and seals. Re-install the pump with a new 15 degree stainless impeller - and - you should bore the reduction nozzle also - paper thin - with a new copper pipe to replace the now missing bilge outlet - silicone around the pump intake channel only.
Replace at LEAST the front crank bearing and all new crank seals ( 3- 92049-3006 ) . Have the top end bored to clean and get a new set of oversize pistons and rings to install - hone to 300 grit with a quality ( sunnen or similar ) hone. An OEM gasket kit will also be needed. Raise the exhaust port 3mm and widen it 2 mm on either side ( 4 mm total ) - “square” off the port shape a bit - raise the intake port 2 mm and lower it 4 mm - leave the ports with an arc ( same call it a smile port - NOT square ) - cut 4mm off the intake skirt of the piston - LEAVING a 10 mm wide section on either side - so the piston does not “rock and fall into a port. Do a GREAT job of chamfering the ports. Most heads are already drilled and tapped and have a brass plug in them near the spark plugs - remove the brass plugs or drill and tap (1/8th inch pipe thread ) new holes. Install 2 new straight brass fittings in these holes. Install that .080 milled head. Install intake manifold and match the manifold to the ports - as good as you can - some are off too far to get a perfect match - do your best. Install an aftermarket exhaust manifold or an exhaust diverter and match those ports also. ( L&S made the first and still the best exhaust manifold - but - others are OK - Westcoast - Jetco - PJS - whatever. Reassemble motor and carefully re-align to newly rebuilt pump shaft.
Hook the water lines up - One each to the newly installed nipples on the top of the head - or - split the ½ inch with a “Y” and then to each one. Run a pisser out the side from the exhaust manifold to BELOW the hull bond line ( so the water will drain from the motor when shut off ) - the other water line from the front of the head - will go to your new pipe. A Westcoast cast type is the best - with as short a body as you can make it - a Coffman is OK - as is a short body PJS. Usually a “T” is installed and another pisser on the other side is used - but - be careful you don’t divert too much water and burn up hoses and waterboxes. Even with three times the water going through - it can still get hot.
Disassemble the carb - install a new 2.0 float valve assy ( 2.2 or 2.5 CAN be used also ) - drill the top end jet ( non-removable brass disc ) with a “42 drill - which is about 1/16 - reassemble with new diaphrams - gaskets can usually be re-used. Same primer as described in the first section. Air filter / flame arrestor - is your choice ANYTHING but stock. Remember - boats don’t need air filters - but - they do need flame arrestors. Set both carb screws at 3/4ths turn out to START. Install carb and hook up throttle and primer.
Any other handling mods are purely personal preference and most are just fine - whatever floats your boat. You will NOT need race fuel - standard 90 octane ( preferably gas - NOT ethanol ) is all you need - a good pre-mix oil ( Redline Racing Oil is best - some prefer 927 ) 50 to 1 mix - this little screamer should have right at 190 PSI - and be in the just over 40 MPH range and get there really - really quick. AND - it should LIVE !!!
You “can” advance the timing - but - for ease of starting etc - I would leave it. 25 degrees BTDC is just fine.
By Cliff Jones