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1996 sylvan offshore 2300 motor issue


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Hi everyone. Stab in the dark here hoping someone may have worked on this boat before. The engine is a mercruiser 5.7 I/o.

I have a dead starter and also a popping at high rpm (backfire occasional) and noisy valves. This is only above 4k rpm.

A marina here is telling me to replace starter the motor needs to come completely out of boat and to do that the floor must be cut out. They initially told me the valve noise was caused by rockers but have since told me the valves and rockers are fine and that it must be cam shaft issue.

Seems outrageous to me that the floor has to be cut to fix the motor or remove it.

Anyone with any experience I would really appreciate some input.

Ps they did oil change, new plugs, and compression test but didn't matter.


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Guest )()()()()()()()()()()()()(

Your popping noise is your rev limiter....telling you you're too high into Rpm, back off the throttle and it won't happen. Get a bigger prop and you can hit the throttle. I know nothing about the starter but removing floor?? To get the engine out???? Sounds crazy to me. I can sit in my engine compartment, see my mounts, etc. your best bet is to arm yourself with some knowledge...I.e. google some stuff. Boat/engine, printable repair manuals, YouTube videos. It's all there. I learned basic mechanics and fix my own 4.7l Merc this way.

Good luck!

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I'm guessing that a 350 GM motor, if that's the case, I know there engines had some cam problems. I had to replace a cam in a Chevy truck. The wear surfaces are just surface hardened. If it wears through the hardening, the cam lobes wear off in a hurry. That would explain noisy valves and you should be losing power also. Can't help with the starter, but if you are in need of a cam in a 17 y/o motor, you might consider a new crate motor. Should be a snap installing a starter then.

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Dear BigMac,

                  Yes the starter removal on a 96 5.7 Mercruiser V-8 in a 8 ft. beam boat can be a nightmare because of the boat mfg's stringer design/location.....But your bigger problem, " back firing under load" should have been evaluated FIRST. What was the compression PSI in each cylinder? It should be approx. 150 and even across the cylinders. If you paid for the comp. check, what were the values in each cylinder?? If you have a noisy valve train, I would suspect one or more lobes on the camshaft have failed. Just examing the spark plugs closely...when removed can tell an educated mechanic what is going on internally. This damage cost should be closely examined as internal engine failures are costly.

Your repair person is chasing a ghost & can be expensive for you. Contact Hank @ L&M/Port Bay or Pugsleys in Ontario, New York also.       ..............................Sincerely, X-Jet Boat Bill in Lewes, Delaware.

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They haven't told me value on comp test yet other than to say its fine. I personally don't think they have a clue what their doing. They burned the starter out on me as it is and are not offering any compensation for that.

My stepdad is a very experienced automechanic and is more than comfortable tearin it down and doin the cam shaft and apparently has a used one already at his shop out of a corvette

The question is can he do the work without pulling the motor completely out? Can he just undo the motor mounts and jack it slightly? And can u get the starter off like that also.

I really appreciate the help.

I'm in ontario Canada so it's a haul down to ontario ny

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Just caught this post BigMac.   Cam shaft canbe replaced if there is approx. 30 inches between the front of the engine and the inside of the engine compartment. If not the engine will need to be pullled. It is easier to do on an engine stand then in the Engine well. You are going to need a lot more then just the CAM shaft. If you are the original owner of the rig, you know the history of how it was taken care of. If not, well, your shooting in the dark. From past experience with the 5.7 in boats, gas in the oil can be a big contributer to cam shaft and premature engine wear. A leaking carburatorcould be the cause or a diaphram in the fuel pump leaking.


Like borderline said, a crate motor, may be a wise choice. 


PS, Putting used parts in like a cam shaft and lifters, isn't always a great idea. Ya might get lucky, but to do all that work, and then not have it work correctly!!!!!  Besides, boat motors have specially ground CAM shafts because of their power band.


Good luck... 

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Is a crate motor not in the 2-3 thousand range?

If block is solid and compression test is ok wouldn't it be worth repairing. Even if its new cam and lifters/rods etc?

Also does it make a diff if I said the noisy valves and back firing doesn't happen until the motor is warmed up? Like 10-15 mins after running at 4k rpm?

A friend is saying it is probably just the coil

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Dear BigMac,

The camshaft may or most likely WILL NOT clear the first bulkhead and fuel tank. Using a Corvette or passenger car camshaft will reduce performance/power in your boat. A Melling cam...MARINE replacement is your best choice. Be sure and use new hydraulic lifters. I would pull the engine and do a valve job/guide repair minimum. I would stay away from "Crate motors." GM uses their Mexico  engine production for all before approx. 2000 year. The Canada "rebuilt" stuff is reproccessed used parts done by who knows who and have 30 day WARRANTIES!! Go slowly here. USE AN EXPERIENCED engine rebuilder with Quality name parts.

......WE have entered 3rd world rebuilding stuff quality....not good for boat engines. Sincerely, X-Jet Boat Bill in Lewes , Delaware

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Dear Big Mac.

                     A Melling marine camshaft #CCS-37 costs about 135 USD from Summit.gaskets another 150. Lifters 100 to 150. Timing chain and gears 40.00. It usually costs about 600...labor to remove and replace the engine unit. If your Step-Dad is on good terms with you, talk him into it. Now an 96 OEM Mercruiser is not the same as a 1996 Car or truck. So save the parts coming out for correct ID WILL NOT BE A HYD ROLLER CAMSHAFT or it MAY BE!! in 1996. TRy contacting KARBELT SPEED & CUSTOM and talk to someone in their shop who is familiar with 1996 Marine Small blocks. Use blue FELPRO head gasgets...about 20 each. This is a somewhat complicated project. This is a standard rotation engine for your I/O application. That is RH as facing the water pump. Good Luck......X-JET BOAT BILL

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Boat is In shop now. Fingers crossed.

Next question. It had a alarm going off solid tone on way in to dock. It did end up stopping after about 20mins. Solid tone is usually overheat but the temp gauge didn't get hot. Could have been a weed I guess in the impeller.

Anyone know the alarm codes for this motor?

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  • 3 weeks later...


Boat is fixed. Issue was cam shaft. I also had them do a tonne of other things to ensure smooth sailing.

Cam shaft



Timing chain

Timing gear



Fuel pump


Not a cheap repair and lesson learned on kijiji but still much cheaper than a new motor.

The issue with the audible alarm was temp related and took them 20 mins to fix. Somehow the water intake hose for the seawater pump was kinked. Fixed that and all is well. Oil pressure aces, runs solid and sounds good.

Too bad a marina couldn't figure this out. Especially the over heating problem since there's only a few reasons why the alarm goes off. I gave the manual for the motor to the mechanic last week and it was all he needed.

Thanks to fieldings tire (Firestone) in Kingston and more specifically Steve, olie and Erik.

If only I could turn back time and not take it to Glenora marina. If I couldn't turn it back far enough to not buy it that is lol

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