1992 Force 70 horse rebuild

MrMarty51

Seaman
Joined
Aug 4, 2020
Messages
51
I had posted a couple of questions about this 70 horse Force in the forum.
It was advised to scrap this engine, but, not having funds to buy a Merc, Johnson or some other more dependable brand, the rebuild was accomplished.
Bored the engine to .040 over, which I too had read was something to avoid, and scrubbed the block several times with detergent and hot water, then checking all measurements and putting it all back together.
Being this is my sons boat I waited until he had time to fire it up. First time on muffs and the engine fired off immediately. I told the son to read the break in procedure in the engines manual.
Next step was getting to some place that would allow an engine, and, operate the boat above wake speed.
Closest place we found was 80 miles to the east, so, away we went.
Got the boat into the water and fired up the engine. Moved away from the dock and got pointed out into the open.
The son started out running pretty hard, the engine is healthy and performs quite well. I asked the boy, did you read the break in procedure ? No, oboy I thought and told him dont run it wide open, and, dont run it at a continuous speed For any length of time, so he did that.
Cruised like that for quite a while and did not run out of fuel, I figured we was getting kind of low so we dumped in the other five gallons and run some more on that. I think we had about three hours run time total and am fairly convinced that the engine should be quite well broke in by then.
Time to see what it would do so we ripped around for a while about as hard as it would go, but stll not running continous at WO throttle.
The engine runs very well, did not overheat and does not go through near the fuel as it did when it was running on two cylinders and one totally dead cylinder too.
The boat, Maxum 1700XR and top speed was 34 MPH GPS speed. Before the rebuild, too speed was shy of 25 MPH.
I still need to check the timing and WOT RPMS but for now, she runs a mighty fine.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
18,037
Good job!! Glad it's working!!
The problem with the 70 is the one carb.
It can starve the top cyl. and not get enough lube?
If it was mine? I'd use a bit more oil .
50-1 is 1 gallon oil to 48 gal. gas.
I'd run 1 to 45 gal.
Not much more but it might make the motor last longer.
Again: Good job!
 

topgun3690

Lieutenant Junior Grade
Joined
May 7, 2019
Messages
1,034
^^^X2....Nice work. It may not be the ideal engine to rebuild, but if it works for you, that is all that matters. (y)
 

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,739
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