1995 Force 70hp

[crobinson]

HelloI recently purchased 1995 VIP stealth 165, with a Force 70hp by Mercury. It was great deal, got it in a divorce sell from a good friend that never used it. The motor was serviced last year and used twice, I was present both times. After I brought it home, the first thing I did was a compression test; all three were at 120psi. From the looks of the motor, it’s never been rebuilt; all bolts look to have factory paint with no wrench marks. While running wide open the motor doesn’t seem to run enough rpm’s on the 15-pitch prop. Presently I don’t have a RPM gauge, boat was not installed with one.I’ve tried to gather all information and history on this boat with very little luck. The previous owner stated that when he bought the boat it was missing the prop and the marina took a prop from a Bass Tracker and stuck it on. I’ve called Mercury, they and another local marina suggest a 10 &1/2 by 13p to help with hole shots because of the weight, that’s the only problem I’ve found so far.According to VIP this boat was a special order, because they only put 75hp on that model boat, and the RPM gauge was standard. From my understanding the boat was bought at a whole sale boat store. I’ve ordered a new prop, should have it by the weekend. Will the 13p prop kill my topend speed (32GPS)and what normal maintenance should be performed to keep the motor running great. I’ve already changed the lower unit oil and plugs, and ran some sea foam threw the motor.BrgdsCory

[roscoe]

Sounds like you are off to a great start.I would also change out the water pump and thermostat.And get a tach. Recommended rpm range is 4750-5250 for that motor.No, the 13p prop will not kill your top speed.The 13p will allow the motor to run about 300 rpm faster, which will make up for any expected speed loss you are anticipating.

[Peter J Fraser]

Best you check your engine RPM's first.The engine will not like to be overspeeded and you need to know what you've got before you make any changes.My Force 70hp ran a 15" prop on my 15' boat. It had no trouble in reaching 5100 / 5200 rpm with full load.I also had a 13" which I used when trolling for trout but it would overspeed the engine if I wasn't careful with a large drop in top end speed.The prop is basicaly the same as Merc 50 and 65 hp so there will be plenty of options available.Rule of thumb.If when at wide open throttle and max speed as you pull slowly back on the throttle the rpm's immediately decay then the pitch is about right or slightly under propped.If however you pull the throttle back along way before you get any rpm droop then you may be over propped and the rig may benefit from a lower pitch prop.Regards Peter

[speeddemon1452]

I have a 1995 70 hp force on my 20ft poontoon it has a 10 1/2 pitch is 13 is what came on it new