Volvo 81 problems

"Have twin volvo 8.1 420 hp in

"Have twin volvo 8.1 420 hp inboards. Two problems; one, both hunt [change rpm] at approx 1200-1800 rpm. Have been told that manifold pressure sensor could be leaking but had that checked and not a problem. Second, after long run and shifting gears at idle, both engines occasionally stall out. Idle settings have not changed. Should I just reset to higher idle? [now approx 600-800- rpm]"

"Richard,

I don't know

"Richard,

I don't know the history of your engines, particularly if this is a new problem or has been evident since new.

I do know that some early 8.1 H.O. engines left GM with the wrong throttle body installed. The throttle body on the 8.1 H.O. is only different from the standard 8.1 in that the idle air hole in the throttle plate is larger (5/16" vs. 1/4"). The small hole causes the H.O. engine to hunt and stall (sound familiar).

Remove the flame arrestor and check the size of this hole. If it is 1/4" drill it out to 5/16", no other change is needed. You may want to remove the throttle body to keep shavings from dropping down into the intake manifold.

Hope this helps,

Good luck
Rick"

Rick. Thank you for the advise

Rick. Thank you for the advise/Richard Wahl

"They may have a different cal

"They may have a different calibration available, too. Rochester deleted the hole on the '01 Masterctaft LTR motors and they had a hard start issue. I saw one of the first ones that showed the problem and after they e-mailed the new program, I went to the lake, plugged the laptop into the DLC, saved the old one and downloaded the new. Took about 5 minutes and since I had told the customer to run the boat hard jest before I got there, it was a verifiable fix.

If this boat is under warranty, let the dealer fix it."