Logo
FULL SITE MENU

1974 Jersey 31b Twin LM318s

M

markman

New member
"Back into boating after being

"Back into boating after being active duty USAF for 23 years. I recently purchased a Jersey brand 31 foot at the water line, twin screw LM318s with velvet drive 1.52:1, prop size unknown at this point. Starboard engine runs good, port engine clatters and smokes a little. Both distributors mechanical advance weights are rusty and I have wiggled them back and forth while applying WD40 to loosen the corrosion. The thing is, the boat only goes 12 MPH @ 2000 RPM. The book states that the motor should go to 4000 RPM and the previous owner states that he did 14 knots crusing at 2800 RPM. Now what gives? The hull is a V shape with a small keel and a flattened V area around the through hulls for the shafts. Is this a displacement hull or a planing hull? It has trim tabs (not working yet) and a nice swimstep. Great wood work and the flybridge is the only steerage as the cabin was configured for maximum living area. Nice boat. Any advice on my dilemna?"
 
"First of all, thank you for s

"First of all, thank you for serving our country.

I suspect the advance isn't timed right, possibly because of the sticking problem. Put a light on it and watch it advance to maximum at 3,000 rpms, then come back all the way as it should.

Jeff"
 
"Mark, Thank you for your serv

"Mark, Thank you for your service!!
Once you check the advance, check to see if the 4 bbls are opening. A sticking butterfly/linkage is not uncommon. Changing fuel filters may help as well and get those trim tabs working!!! Speed is greatly influenced by the hull condition. Is it clean?"
 
"Hey guys,
It was my privileg

"Hey guys,
It was my privilege to serve. I cleaned the bottom of the boat and it could use a new coat of bottom paint. The sticking butterfly sounds like I need to go over the carbs. I have only squirted them with Choke cleaner and WD40. Fuel filters were the first things that I changed. I have Bennett trim tabs and I think the motor may be bad or the slave cylinder is stuck. When I cleaned the bottom the cylinder was encrusted with junk. I left the tabs in their position that I purchased the boat with. The position is with the aft edge pointing down thereby applying downward bow. Correct?"
 
"Mark,
I have a 31' 79 si

"Mark,
I have a 31' 79 silverton from NJ and had the same problem. I was getting max 10 knots at 2800 rpm. noticed that the trim tabs were not holding due to a leaking compressor. After that was fixed i was able to get abut 14 knots no problem at 3000rpm. Stil not ideal and too slow for me but i blew the starboard motor and will be back at it in the spring."
 
"One other thing to check: Bar

"One other thing to check: Barnacles on the prop blades. It doesn't take many of those little ~*@^ to keep a boat from planning off. Mine leaps out of the water at half throttle, yet it would not plane at all with only one prop covered. How the other was barnacle free remains a mystery.

Jeff"
 
"Scrubbed the props too. On t

"Scrubbed the props too. On the idea of the coreolis effect (CE), the way water spins as it goes down the drain, may I suggest that your clean prop would be the other one if you boat was south of the equator as the CE is reversed down under. LOL"
 
Back
Top