90-HP Mariner 3-cylinder Surging
Posted: Wed Jan 11, 2017 5:43 am
I'm a new guy on the block from South Africa and hello to all. Yours truly stay out in the countryside and have no boat repair shop nearby to contact and have to do repair things myself.
I have a Mariner 90-HP three-cylinder (mid 1980's model) with the following problems. When accelerating hard from standstill she would take off fast, then have a slight hiccup or surge (momentarily for a split second or two) and then take off like a bat out of hell. Next time she would take off fast and clean out of the hole for a few times, then have the hesitation again at another time.
Furthermore, after pulling away, she would continue to accelerate hard at WOT, run smooth and then start surging slightly in a "go/brake" fashion. When back at idle, and accelerating hard the same would happen again at WOT. However, running about half throttle the surging seems less and takes longer to take effect at speed; sometime she would run cleanly at mid throttle. What is causing this malady?
I serviced the engine and also fitted a new petrolpump kit which I suspected to be the culprit but now seemed not to be. All fuel hoses are good and not cracked.
The carburetors are properly cleaned, air screws out by one-and-three-quarter turns and carbs also properly synchronized. Timing is set with a timing light at 3-degrees BTDC at 800rpm idle and WOT 23-degrees at 2500 to 3000rpm. New gapless NGK - BUHW-2 spark plugs are fitted. Compression is fine at 800-kpa for all three cylinders.
I believe the tuning specs are okay because, as said before, sometimes she will jump away cleanly and accelertate hard to WOT before the surging action starts. Likewise with the pull away at WOT, sometimes clean and at another time with slight hesitation. If timing were off, surely the hesitation would be evident permanently--or am I missing something?
Can this problem be electrical? Or, perhaps something else?
Lastly, I noticed some fuel drops dripping from "Solenoid enricher valve". Can this be the cause as I understand this is only a choke device use in starting only.
Help would be greatly appreciated. Thank you
I have a Mariner 90-HP three-cylinder (mid 1980's model) with the following problems. When accelerating hard from standstill she would take off fast, then have a slight hiccup or surge (momentarily for a split second or two) and then take off like a bat out of hell. Next time she would take off fast and clean out of the hole for a few times, then have the hesitation again at another time.
Furthermore, after pulling away, she would continue to accelerate hard at WOT, run smooth and then start surging slightly in a "go/brake" fashion. When back at idle, and accelerating hard the same would happen again at WOT. However, running about half throttle the surging seems less and takes longer to take effect at speed; sometime she would run cleanly at mid throttle. What is causing this malady?
I serviced the engine and also fitted a new petrolpump kit which I suspected to be the culprit but now seemed not to be. All fuel hoses are good and not cracked.
The carburetors are properly cleaned, air screws out by one-and-three-quarter turns and carbs also properly synchronized. Timing is set with a timing light at 3-degrees BTDC at 800rpm idle and WOT 23-degrees at 2500 to 3000rpm. New gapless NGK - BUHW-2 spark plugs are fitted. Compression is fine at 800-kpa for all three cylinders.
I believe the tuning specs are okay because, as said before, sometimes she will jump away cleanly and accelertate hard to WOT before the surging action starts. Likewise with the pull away at WOT, sometimes clean and at another time with slight hesitation. If timing were off, surely the hesitation would be evident permanently--or am I missing something?
Can this problem be electrical? Or, perhaps something else?
Lastly, I noticed some fuel drops dripping from "Solenoid enricher valve". Can this be the cause as I understand this is only a choke device use in starting only.
Help would be greatly appreciated. Thank you