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Gen Vl 330hp help moving 18000#’s
Looking for some help on my new to me cruiser. Boat is a 1997 Maxum 41scr. Weight is around 18000 pounds. Motor are carb 7.4 gen Vl 330 hp with just under 900hrs. Port motor pulls 4400 rpm , starboard motor only 3900 -4000 rpm at 3/4 throttle, anymore throttle motor will just lay down and make more air into carb noise. Boat runs right at 29 mph @ wot. Cruising at 3600 rpm boat runs a smooth 22mph. Looking for more rpm out of the starboard motor I pulled the plugs. #4 looked wet and rust colored. Than I did a compression test. 130 - 115 on all but poor #4. #4 was only 110 and that took many cranks, 100 at the same 6 cranks as the rest of the cylinders to max out. So now a leak down test. Cylinders with 130 compression where 15% leak down, 120’s where up to 35% ,115 cylinder was 52% and poor #4 was over 70%. Most leaking was out the exhaust and come past the rings. So I pulled the heads and found signs of water marks on # 4 cylinder. Now I am at a cross roads, rebuild the stock peanut port heads and put it back together over looking the water marks. The rest of the cylinders look good, no ring groove to top of cylinder and the 130 pound cylinders still show cross hatching. Or pull the motor and rebuild. And rebuild back to stock or try to get more TQ so I can run a larger prop at a lower rpm to get better cruising mpg. Thanks for any input. Bryan Oh yes one more thing when did 35% prop slip be come normal. I had no clue shat drive cruisers ran that much slip. |
I can run a larger prop at a lower rpm to get better cruising mpg. My buddy has a 2000 Maxium 37 SCR with V-drives, 385hp 454 MPI and V-drives are not fuel efficient. The good thing about shaft drives is if you can hear a rattle when the boat is ideling in neutral, then there is a miss in the motor. I would think rebuild time. And yes, those tunnel drives (what I call them) prop slip is real high |
Where was the water coming from? I don’t know about engines in a cruiser but 900 hours seems like close to rebuild time anyways. |
Looks like water was coming in from the exhaust manifolds. Motors are fresh water cooled and that motor would loose fresh water out of the closed cooling system. Also the coolant would turn a rust color. The exhaust manifold on the even # side was real rusty. The water marks on the cylinder is only on the top 1/4 of the bore.
I am on the look out for a set of peanut port heads. I do not really want to send a ton of money rebuilding these stock heads. I am the second owner of the boat. The first 21 years the boat was on Lake Washington. The last two years the boat was on salt water. As the hr's go I have put about 20 hr's on it so far and it seems to run good at lower rpm's. I think the rev limiter is around 4400 or so for inboards ? |
Originally Posted by Baja Rooster
(Post 4713710)
Where was the water coming from? I don’t know about engines in a cruiser but 900 hours seems like close to rebuild time anyways. My buddy Scott has 2700 hours on his bb 350 horse crusaders in his 42 double cabin fly ridge .Silverton. Ran it on plane all the way down to Florida from Michigan without a Hiccup a few years back. They sill fire up immediately and purr. Rebuild the heads and carbs and let em rip |
I figured as such. New risers and refresh the heads and let her rip! Would newer Edelbrock Performer manifolds be an upgrade since they’re off already? I wouldn’t mess with the proven recipe too much though.
Originally Posted by tommymonza
(Post 4713729)
900 hours is nothing on those bone stock 330s. We used to run them for 4000 in the parasail boats back in the day Replaced them just because we were afraid blocks might be corroded from saltwater. My buddy Scott has 2700 hours on his bb 350 horse crusaders in his 42 double cabin fly ridge .Silverton. Ran it on plane all the way down to Florida from Michigan without a Hiccup a few years back. They sill fire up immediately and purr. Rebuild the heads and carbs and let em rip |
Thanks for all the input.
I am replacing the stock exhaust manifolds with these Hardin Marine Seaward manifolds https://www.hardin-marine.com/p-8543...st-system.aspx And replacing the intake manifold with this Weiand street warrior intake. https://www.jegs.com/i/Weiand/925/81...SABEgJS1_D_BwE Not so much looking to get more power but I just cant help myself to make it lighter on my back going back together. |
Looks like you’ve got it pretty well sorted out. It might be worthwhile to throw a wideband sandwich adaptor on their if it’s available. Fresh heads and manifold with some tuning on the carbs might really clean up the midrange for your cruising and improve fuel consumption as well. |
check heads for craks before you put any money in them,peanut port heads are a dime a dozen if you need to replace them ,also replacing the exhaust manifolds&risers is a must.don,t waste your money on new intake manifolds,you will gain no performance and the small weight saving is worthless in an 18000 lb boat.
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If you are dying for aluminum intakes, Edelbrock offers most of their Performer series with bronze/brass water pasages for marine engines. Look under their Marine series of parts.
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