First time out after motor swap

Thursday evening was the first time out on my new to me 1995 21ft Suntracker, it did have a 70hp Force (by Mercury Marine) motor that had a bad power head when I bought it. I had a 75hp Mariner that I installed. I have to say I was pleased with the outing except for one little problem that the Mariner has and has always had when it was installed on another boat, that's when either pulling up to a dock or loading on the trailer the motor will die every time at low rpm. Just barely bumping the throttle up a tiny bit and no problem with motor running but you really can't do that pulling up to a dock or loading on the trailer.

The tach on the Suntracker shows to be working "sometimes", but seems very erratic (jumps around),so I'm not getting a true reading as far as wot rpms. Now I did take my hand held gps with us and with what I would estimate weight wise with two people and gear would be around 500 lbs for this outing. I have checked my little gps several times with my truck speed and it is pretty much dead on with the speed odometer. Checking the Suntracker Thursday I showed a highest reading of 23.4 mph but mostly stayed in the 22mph plus change speed range, most all reading heading into a between 10 to 15 mph wind, bimini top was rolled up and at the half way point, not laying all the way down that is. So am I in the ballpark as far as speed goes for this size of pontoon? I'm running a aluminum 13 3/4 x 15p prop.


Tony

Re: First time out after motor swap

22 mph is on the high side of normal so all seems good. I read somewhere that some tachs have different settings for different brands of motors. Maybe look into this before tearing things apart to fix it.

Re: First time out after motor swap

Yes that sounds about right for speed. But I wouldnt run it at WOT untill I had made sure of the RPMs , you dont want to over rev the motor.

The idle problem may be as simple as adjusting it higher or the carb may need a rebuild.

Re: First time out after motor swap

Thanks for the replies guys, I have never had the carbs serviced or even changed out the spark plugs, I cleaned and looked at the plugs, and they looked ok I guess, little different plug then what I'm use to.They have a probe style electrode probably pre-set instead of one you set the gap. Motor seems to run great when you open it up a little. Even at a low idle it does just fine, just not to low though. Maybe a trip to boat motor mechanic is due, hopefully it will do the trick. I did the water pump last year myself, but have never tackle carbs on a boat motor before.

Re: First time out after motor swap

Run some sea foam through it, that will clean it out and if its a carb gum problem it should fix it and put in a new set of plugs. Then see how it acts, no need to put it in the shop unless you just have to.

Re: First time out after motor swap

MH Hawker you must have been reading my mind, I have done the seafoam and have kept it added to each fuel mixture. That was my next try was new plugs, I have owned this motor since 1997 and as stated never changed the plugs, hopefully that could be the culprit for my low idle problem. The motor set up idle for about 6 years, last year I pulled it out of it's little retirement and first thing I did was replace the water pump. At that time added fresh fuel,2-cycle oil,ethanol treament, and seafoam. After about 10 cranks she fired off. Again new spark plugs are the next thing to try, fingers crossed.

Re: First time out after motor swap

It should also have a idle adjustment screw to raise it a bit to keep it going.