Boatbuilder Connection

Posted by Bruce Humphrey on April 07, 19102 at 20:12:29:


After 3 months of building the engine for my chriscraft runabout, we got everything hooked up finally, and started it......and after a few minor glitches, it ran!

A little background:
a V6 is all that we could fit in this boat...19 ft classic barrelback..... looked into using a V6 vortec motor from a car, but given all of the mods in marine motors, decided to buy a base marine block with pistons/ intake from GM (about $2k new). From there we bought parts everywhere to build the motor... EFI with throttle body, computer, and harness from Holley marine, new 4 inch exhaust manifolds and elbows to match mercruiser from Aquapower, bell housing, starter, alternator, brackets from a junked mercuiser...sandblasted and powder coated all, rebuilt the starter and alternator, built up a new wiring harness from scratch, velvet drive tranny from a local dealer who gets new engine/tranny combinations and didn't need this tranny.. bought an aftermarket full-closed cooling heat exchanger and jabsco raw water pump (to match mercruiser)

we started it today...had a fuel leak to fix, and an oil gusher from an open oil plug in the block we neglected to plug.... oops! first try the engine backfired because the distributor was off 180 degrees....fixed those problems and she runs beautifully!

we watched the temp climb to 190 degrees, and stopped the engine.....we had already put 3 gals of coolant in, but turns out it needed another 1.5 gals of coolant......
turned it back on, and she settled in around 170 degrees in the end, i doubt we saved much money over buying a brand new engine/tranny from marine power..maybe saved $500 or $1000, but we learned a hell of a lot about how these things go together......

my advice to anyone planning to do this....if you've got lots of time....go ahead, but there are an incredible number of little parts to put these motors together...and it takes a lot of time!

if anyone is thinking of putting EFI on an engine, email me....i learned lots about the Holley EFI which I can far the product works very well, but the documentation is a little weak....but kind of cool to use a personal computer to build a fuel map for your engine!

Posted by Mark Bronkalla on April 07, 19102

In Reply to: The engine starts! posted by Bruce Humphrey on April 07, 19102 at 20:12:29:

Congratulations Bruce

Lots of guys think about doing what you did but few try (or do it and then keep quiet about the results).

How about a materials and suppliers list? Any hints, tips, etc.?

The "roll you own" EFI is really cool. What did you use for instrumentation (or did you feel none was needed) to verify mixture and HP output?

One of the fun things of building your own is knowing how to fix it when things need maintenance and repair. You are now a full step ahead of many of us with pre-built EFI engines.

Posted by Bruce Humphrey on April 08, 19102 at 05:49:23:

In Reply to: Re: The engine starts! posted by Mark Bronkalla on April 07, 19102

Mark, I'll put together a materials/supplier list and post it.

Regarding your question about instrumentation: The holley EFI comes with a computer interface so you can monitor all sensors on a PC while tuning the engine. For the mixture control, I installed an oxygen sensor in the exhaust to provide "closed loop" feedback to the engine computer for controlling mixture....this sensor is optional in marine applications, and commonly not installed in marine EFI, but I was advised that it is the best way of monitoring combustion efficiency. Regarding HP output, I don't know how to do that without putting the engine on a there some other way that you know of?

Thanks to you Mark, and many others on this board, for advice on this guys were a big help!