2005 mastercraft with indmar 8100 vortech no power in geat

[zguy87]

Launched my mastercraft yesterday with a indmar 8100 vortech in board, and unfortunately it won't go over 2500 rpm in gear. It idles really rough like it's got aggressive cams or its missing on a few cylinders. If you rev it up in neutral it'll back fire from the intake then clear out and rev fine. As soon as you put it in gear and try to accelerate it backfires again and won't rev over 2500 rpm.

Compression is 140psi in each cylinder. Fuel pressures at 35PSI AND I have spark at each plug. It feels like the timing is out of whack

Any help would be appreciated.

 

[alldodge]

Don't have the 8100 Indmar manual (8.1 or 496) but my first thought is the position sensor has an issue. This engine even in a Merc has a computer which should provide some needed info. Figuring the codes have not been checked yet. How long have you had the boat and when did this start

 

[zguy87]

I got the boat last febuary in trade for some mechanical work I did. It had partially sunk at one point but the motor fired in the guys drive way.
I only launched the boat yesterday so it's new to me.

When you say position sensor are you talking the gear position sensor or throttle position sensor?

 

[alldodge]

partially sunk

Water and electronics is never a good thing, even more so if it was salt water. How deep was the water?

Does the motor make any beeps when the key is first turned ON, or other times while running?

There are two position sensors, a crankshaft and camshaft sensor. The two sensors tells the ECM when to fire the individual coils. I would start by removing the plugs and see what they look like. Then remove check/clean the coil connectors and position sensors.

 

[zguy87]

That would make sense. Thanks for the help. I guess I'll have to call indmar and see what tests I can preform to check those sensors. Is there an online resourse where I can find the manuals?

 

[zguy87]

Just to answer your question. It was fresh water and it looks like it got up to the top of the crank pulley. I have no alarms going off either

 

[zguy87]

Spent a little time working on it today. While running it I pulled the cam pos. Sensor connector and bam it revs fine w/ no backfiring. I have a check engine light on with it unplugged but I think that narrowed it down. Thanks for the help

 

[alldodge]

Was out of town. The motor gets position info from both sensors. The check engine should be the computer says HEY, I have no cam sensor reading. I'm thinking that it could be either sensor which could be the issue. One says one thing, and the other another, so conflicting info.

Could really use a scanner.