Marinette Boat Forum

Trying to figure out how to add a pic

21 mph is the expected performance for 318 I think... You won't get better for 360 or 440. It's a light boat for a 318. Twins would go faster (I had twin 318's on the Fortunato I). I agree with Jeff, stay with the one 318's. A 360 is the most I'd go, and it's a hard sell.

For me, I would strip the old engine of anything I expect to keep ... immediately and store it. Mostly, I never reuse parts unless I have to... Fresh water cooling, starter, Electronic Ignition, yes, Water pump maybe, carb maybe... etc.

Also have the old and new engine checked.

My questions to the seller ... Is compression OK, tested? How much is the newer engine? Valves Ok? How many hours? IS IT THE SAME ROTATION? Does it come with the Velvet drive? Oil test OK? One that you sample and send it to AMSOIL.

A rebuilt long block swap may be cheaper in the long run. Used engines have no warranty.

I'm seeing some good prices on rebuilt 440s and am strongly considering it since my single 318 won't go any faster than 10 knots. Super frustrating since I see posts like this one suggesting I should be going double that speed. Hell, I'd be happy going 15.

Anyone have any experience replacing a single 318 with a single 440 in a 28 express?

I know the engine is much bigger but does it fit in the hole and do the mounts line up the same?

Should I do any checks to my existing engine to address the lack of performance?

Somethings definitely wrong if you're not getting but 10 knots. I put new points in my 72, 28 Express, single 318 (original) this past week and at wot, 3,000 rpm on my boat, got 23 mph. 2,000 rpm will give me 15 mph which is my favorite cruising speed. Speeds posted as read off my GPS. Too many top notch mechanics on the forum not to get this figured out, tho I'm certainly not one of them. Good luck
Rockxx

Agreed. Something is off here for it not to be able to plane off.

The most logical suspects are: Prop bad or fouled (it doesn't take much), distributor advance frozen (common problem), carb secondaries not opening (or otherwise messed up), dropping cylinders under load (faulty ignition).

Good luck!

Jeff

Interesting.

My carb is a new one (2 months)
The prop is a new 14x11 (I cant push the engine to turn more than 3200 with it - basically half throttle)
I did the pertronix kit upgrade with coil
My engine supposedly has 96 hours on it

I guess I should start by looking for drag on the bottom of the boat (maybe an anode bent off and is dragging) & getting another gps and stopwatch

I'll throw the gps in my car and see how that reads today

After you did the pertronix conversion, did you check the timing? I have seen timing changes of almost 10 degrees just by installing these kits. Not all the time, but at least 3 or 4 times a year.

No, I'm not sure I know how to do it but I followed the compression instructions when I upgraded (my cylinder hit like 90+ psi if I recall correctly)

I'll look up how to do that

well, gps works fine. I'll look at the prop and do a timing check

Adding the Petronix unit doesn't change a sticky advance unit. I recommend 'exercising' the mechanism now and then by manually flipping it back and forth a few dozen times (or more). Also, you need to add a few drops of oil to the felt just below the rotor.

On checking the timing, the advance should be all in below 4,000 rpm, and go RIGHT back to the idle position when you idle her back down.

Jeff

PS: "It ain't obvious, Ma-am..." (from some obscure movie) but the timing has often been set with the advance stuck partly way out. Since it will go back to where it should be at idle--now and then--one ends up with a 'mystery' stalling problem. (Ah-hem!)