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I need help with my mercruiser 898

D

donny_a54

New member
I have purchased a 1981 formula thunderbird last year. It has a mercruiser 898 in it. very good shape and i have put some money in it to try and make it run right. i switched the carb over to a 4barrel because i had it laying around. well my problem is with the engine is that it will run for about 10 to 15 mins. i go and shut it off and turn it back on it will stall when i try and put it into gear. this has happened to me twice now. the guy that fixed it told me it was ready to go and kinda took my money from me. i have been told it could be the shift interrupter. if you guys have any input on how i may fix my problem it would be greatly appreciated. i will answer any questions. please help me thanks Don
 
The shift interuptor is working correctly

It could be a couple of issues, bad short shift cable, shift mechanism at gimbal housing does not move freely.

Here is my adjustment proceedure and some specifications on cable wear.

Trim out drive up 2 inches from all the way down.
Take keys out of ignition!!!!!!!!!!!
Have a second person stand at the prop.
You, remove the short shift cable from the shift bracket.
After the cable has been removed, push the plastic cable end all the way in and hold in place while prop is being spun C’Clockwise..
Have second person rotate prop counter clock wise until the prop is fully engaged and wont turn anymore. Maintain light effort on shift cable plastic end pushing it to keep forward engaged.

Measure the distance from the center of the brass trunion to the center of the round mounting hole in the plastic end. Adjust trunion to make that distance 6 inches. no more no less! In cases where the shift cable is old but still works well you can adjust this dimension to 5 15/16”. NO MORE.

Put shift control handle in forward FULL throttle position.
Remove the control shift cable from shift bracket at this time.

Install short shift cable back onto bracket at this time.

Take the shift control cable and adjust the trunion so it fits perfectly back into the shift bracket.
Before installing it turn the brass trunion 4 complete turns away from the plastic end and reinstall into shift bracket.

Now put shift control handle in the neutral position.
Have second person spin prop, it should spin freely.
Put shift control into the forward detent position at ~ 10:00 position. NO FUTHER.
Have the second person rotate the prop counter clockwise. You should have solid engagement with no ability to continue to turn the prop.

Now shift back into neutral. Prop should spin freely with no clacking or clunking.

Now shift to reverse to the 2:00 o’clock position detent NO FURTHER!!

Have the second person spin the prop clockwise.

If you have positive engagement with no clunking or jumping out of engagement, you are done.

If it does not fully engage into reverse than look at the shift bracket where the short shift cable mounts and there is a slot. Loosen the 7/16 hex that is touching the bracket and move the stud so you are pulling the short cable.

Try this and retest in water under load.

Anyway there are tests that would tell you if the cable is bad but to difficult to type out here but in general if you remove the shift control cable from the shift bracket, shift the control handle to full forward/wide open throttle and make a mark on the cable end, now go full reverse and repeat. Measure distance between marks, (2 7/8" to 3 1/8") any more and replace the control cable.
 
That is a marine carb ?

I think your lower cable went.

With water going to your drive start the engine, see the micro switch... press it if the engine wants to stall that ain't the problem.

Get a manual and a lower cable.
 
thank you guys. i will be getting my boat out of storage here in the next few weeks. i will keep you guys posted on what i find out. thank you very much for your input
 
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