PlayD0h
Petty Officer 1st Class
- Joined
- Apr 23, 2009
- Messages
- 326
81 70hp Sea Horse tuning questions. Tach & Timing light (buy/install) Idle & WOT help
Hi
SO I have an 81 70hp sea horse, on my 16' Starcraft Aluminum boat. I've put a new prop on it, new water pump, plugs, and just overhauled the carbs. It starts and runs nice, although I have a few minor issues.
Firstly it seems to idle just a bit too high and grinds just a bit going into gear. Not unusually, but I feel its idling above 1000 rpm. Which brings my first question on installing, and/or connecting a non-permanent Tachometer. I've done a bit of searching and I'm assuming a "teleflex" tach is what I'm after. I also read that a timing light with tach is handy, and I really only need a Tach to tune and inspect the motors performance. I'd like to spend as little as possible, but don't want to second guess the readings either.
Next, I feel like the motor isn't reaching max power/speed. I just used a 10 year old Garmin Etrex H GPS and it says I'm going 27 mph (44 Kph). It feels a lil bit faster then that, but when I push the lever all the way forward, I can push it fairly hard and get it to go a bit further & go a bit faster. Also after a min or so, it slows down a tad and I need to push the lever hard again.
It doesn't seem to reach WOT or rev as high as it should/could. It takes off good and runs smooth. It did slightly stumble and occasionally stall when trying to accelerate quickly, but the carb overhaul seems to have fixed that issue.
I did a compression check and found all 3 cylinders at around a bit under 110, very even, but seemingly low. I'm not sure if its underpowered due to compression/worn rings, or if I need to adjust max throttle. Maybe both.
I have a couple service manuals, but don't see a straight forward "Throttle stop" or "max throttle" adjustment, and all the procedures call for a Tach and Timing light which I don't have. Advice on what Tach and Timing light to buy, or features/spec to look for in one would be greatly appreciated.
I'm going to check the manuals Throttle cable adjustment, which calls for the Throttle lever to come back and touch the Idle stop screw. I should have checked this "Before" asking here, but I need Tach and Timing light advice also.
I've read there's 3 wires in a Tach, +, -, and sensor. I'm not sure where on my engine or controls this "sensor" connection should be. seems pretty straight forward, but I think I'm misunderstanding something. :facepalm:
All in All, I could live with how its running now, and I suspect it could be just a worn and tired motor, but the Lever issue makes me think I can fix it, and fairly easily.
Hi
SO I have an 81 70hp sea horse, on my 16' Starcraft Aluminum boat. I've put a new prop on it, new water pump, plugs, and just overhauled the carbs. It starts and runs nice, although I have a few minor issues.
Firstly it seems to idle just a bit too high and grinds just a bit going into gear. Not unusually, but I feel its idling above 1000 rpm. Which brings my first question on installing, and/or connecting a non-permanent Tachometer. I've done a bit of searching and I'm assuming a "teleflex" tach is what I'm after. I also read that a timing light with tach is handy, and I really only need a Tach to tune and inspect the motors performance. I'd like to spend as little as possible, but don't want to second guess the readings either.
Next, I feel like the motor isn't reaching max power/speed. I just used a 10 year old Garmin Etrex H GPS and it says I'm going 27 mph (44 Kph). It feels a lil bit faster then that, but when I push the lever all the way forward, I can push it fairly hard and get it to go a bit further & go a bit faster. Also after a min or so, it slows down a tad and I need to push the lever hard again.
It doesn't seem to reach WOT or rev as high as it should/could. It takes off good and runs smooth. It did slightly stumble and occasionally stall when trying to accelerate quickly, but the carb overhaul seems to have fixed that issue.
I did a compression check and found all 3 cylinders at around a bit under 110, very even, but seemingly low. I'm not sure if its underpowered due to compression/worn rings, or if I need to adjust max throttle. Maybe both.
I have a couple service manuals, but don't see a straight forward "Throttle stop" or "max throttle" adjustment, and all the procedures call for a Tach and Timing light which I don't have. Advice on what Tach and Timing light to buy, or features/spec to look for in one would be greatly appreciated.
I'm going to check the manuals Throttle cable adjustment, which calls for the Throttle lever to come back and touch the Idle stop screw. I should have checked this "Before" asking here, but I need Tach and Timing light advice also.
I've read there's 3 wires in a Tach, +, -, and sensor. I'm not sure where on my engine or controls this "sensor" connection should be. seems pretty straight forward, but I think I'm misunderstanding something. :facepalm:
All in All, I could live with how its running now, and I suspect it could be just a worn and tired motor, but the Lever issue makes me think I can fix it, and fairly easily.
