1975 70 hp Johnson, died putting boat on trailer

[cvlngineer]

Hello,<br /><br />I just purchased the motor mentioned above, and had it rebuilt. I took it out to test it today, and it seemed to run fine. I went to load the boat up on the trailer, and when I got the front of the boat up on the runners and gave it gas to slide up the trailer, the motor died out. It seemed like it was lugged down or something. <br /><br />I am also curious about the speed of the boat. This boat ran about 26 mph with my old 30 hp motor with just myself in the boat, and I could only get 32 mph out of it with the 70 hp. I am not a speed demon by any means, but I was expecting it to go a little faster. The boat hull only weighs about 650 lbs. <br /><br />I did run an oil-rich mixture in my first tank today, since the motor was rebuilt. I added about 23 oz of oil to the 6 gallons of gas. Could I have possibly fouled my plugs already?<br /><br />Does anyone have any ideas as to what could be the cause of this problem? The motor runs fine other than the trailer incident.<br /><br />Thanks,<br />cvlngineer

 

[OBJ]

Re: 1975 70 hp Johnson, died putting boat on trailer

Hi cvlngineer,<br />Do you have a tach in the boat? If so, what kind of rpms did you see. Was the sync and link set correctly and was the engine properly timed? I don't think the extra oil caused the problem. Check your compression and spark and see what you get. No spark and an ignition component has failed. Re-check the fuel system for leaks and check the fuel line and primer bulb are ok. Let us know what you find. One more question, were the carbs rebuilt along with the engine?

 

[ob]

Re: 1975 70 hp Johnson, died putting boat on trailer

It's possible that the plugs have begun to foul.A visual inspection would confirm.If they are fouled they won't just appear wet but rather bridge gapped.<br />It is also possible that the carb synchronization is out of adjustment in relation to the ignition timing.It doesn't take much.<br /> It is difficult to make any carb mixture adjustments until the oil rich breakin is complete.

 

[cvlngineer]

Re: 1975 70 hp Johnson, died putting boat on trailer

Thanks for the speedy replies. <br /><br />I haven't added a Tach yet, but that will be my next purchase. Running at WOT, the rpms sound like they are normal, and the engine runs smoothly out on the water. <br /><br />As far as I know, the timing and everything was set properly. The carbs were rebuilt and the water pump was replace.<br /><br />The compression is 135, 135, 137 I checked this before I considered buying it.<br /><br />The fuel line and primer bulb are brand new, but I will double check them.<br /><br />I appreciate the help!<br /><br />cvlngineer

 

[slow_boat]

Re: 1975 70 hp Johnson, died putting boat on trailer

You did not state as to whether or not the engine had been 'broken in' before you bought it. If not,it might not be a good idea to run it much at WOT until it is.

 

[cvlngineer]

Re: 1975 70 hp Johnson, died putting boat on trailer

slow boat,<br /><br />It is not a complete rebuild (no new pistons, etc) so the head hasn't been pulled, and no new rings or anything. The powerhead hasn't been run in quite awhile, so the guy told me to run an oil-rich mixture through the engine for the first 6 gallons of fuel. <br /><br />You do make a good point, though. I didn't run very long at WOT, I just kicked it up there after the engine warmed up a bit to see how it performed.<br /><br />Thanks,<br />cvlngineer