898 merc timing jumping

The timing is jumping 4 to 6 d

The timing is jumping 4 to 6 degrees and im wondering what it could be. Runs good under load but it lacks power only getting 3600 rpm at full throttle. Any help would be appreciated

Is the engine surging? What i

Is the engine surging? What ignition system?

Its not surging at all souds g

Its not surging at all souds good but just not able to achieve top RPM. I put a timing light to it and its jumping I was thinking it could be the timing chain??? Its a 305 merc and its sluggish out of the hole and its only pushing a 19 foot boat. RPM normal is 3800-4200 and its only getting 3500 trimmed.

Shawn
Timing jumping around i

Shawn
Timing jumping around is usually indicative of loose bushings on the distributor shaft.
Bert

Pull the dist. cap off and bum

Pull the dist. cap off and bump the starter until the rotor is pointing forward to the bow. Use a breaker bar and socket and rock the engine while watching the rotor. The rotor should move with the rocking w/o delay. If not; replace the timing chain.

thanks for the help i will try

thanks for the help i will try that in the morning

"Is this problem new?
What pr

"Is this problem new?
What prop are you using?
2 bbl carb, right?
Are your throttle butterflies opening fully?

I had an 898 in an 18 ft Webbcraft bowrider a few years back. It was a dog until I put a 19" pitch prop on it. (The idiot I bought it from had a 23" prop on it.)
After that it would hit 4600 WOT and the hole shot really woke up.

Rod"

I have a 19 pitch on it right

I have a 19 pitch on it right now. The prop is not the issue im pretty sure. The problem is new this year and it is a 2 barrel carb and i am getting full throttle. Going to check the distributor shaft bushings now! I will report back in a bit! Thanks for the help guys!!

"With the engine running and t

"With the engine running and the timing light connected and pointing on the timing mark, Do you have timing advance biult into your timing light?

If so Rev the engine to 3000 rpm. Set your timing light to ~ 32-34 degress before top dead center.
The timing mark should line up pretty close to 0 on the timing mark/pointer on the motor. Also as you release the throttle watch the mark closely and if it is occilating badly you most likely need a timing chain. I do not belive that a stretched timing chain would limit full throttle rpms. It would most likely cause starting and diesling issues.


What year is this???
Is it a thunderbolt ingition?
What spark plugs are in it and what are the gaps set at?
What is your initail timing set to?"

Im glad to report back it was

Im glad to report back it was only a loose spark plug. Thanks everyone for the advice and keep up the great work!

Boy if only all our problems w

Boy if only all our problems were that simple! Glad to here it wasn't something really expensive.