9.9 to 15 conversion

[MH Hawker]

Re: 9.9 to 15 conversion

Thought I would give a up date. After around 45 hours of running time its still working fine the RPMS are holding very well even with 5 adults on board.

 

[MH Hawker]

Re: 9.9 to 15 conversion

I finely got around to running a fuel test. Put one gallon in the tank and ran it till it ran out, Last year I got 28 minutes of running time at WOT and a distance of 4.5 miles, this year after the conversion to 15 hp I got some unexpected results, more or less the same conditions with a bit heaver load I got 35 minutes and 5 miles. I was expecting the mileage to drop off due to the higher HP but it looks like I lucked out and hit a sweet spot.

 

[Sea Rider]

Re: 9.9 to 15 conversion

Is that a rebadged Yam or Tohatsu 9.9 engine ? A 20" footer with a 15 HP engine + 6 boaters is a poor performer. With current prop and load go for a wot spin adding boaters accordingly to achieve at least 5500 revs at wot. If boating with 6, match a prop that gives 5500-5800 so engine runs middle to near max rpm factory stated for than engine.

If achieving 5000 or lower rpm while running medium to highly loaded boat, you're lugging the engine. It's good to have at least 2 props, the standard to move light to medium loads and a extra for medium to heavy loads.

Happy Boating

 

[MH Hawker]

Re: 9.9 to 15 conversion

I am on a limited hp lake by choice so its one of those things I have to live with and I am very lucky that the motor is one of the de tuned ones that a simple carb swap brought it up to 15. I have often wondered how many run the limited HP lakes around here we have lots of them so its common.


I am pretty sure its a Canadian made merc or at least a final test and inspection sticker on the side of the power head says it is. But the ser is 0G119661 on a 1996 mariner. With 2 on board its hitting 5600 RPMS and with 6 it drops off to 5000. Before the change it was at 5200 and with 6 it dropped off real bad to 4000, one of the reasons for the HP change.

I do have a 5 1/2 3 blade work boat prop as a spare but I have been thinking on a 4 blade prop for when I have a full load just for that reason, I presently have a 7P 3 blade and a 6 1/2 P is the only one I have been able to find in a 4 blade and that should be just about right I would think but on these low HP motors its real limited on prop selection, But I have been real slow getting around to it. Its been a bad year here for boating lots of rain so haven't had to may days to go out and when I could lol I ended up with several on board. I think they were waiting on me to go out the door to see if I was going out to the slip. I have managed to clock just over 60 hours and its just now getting decent weather. And honestly I may have a full load of 6 may be once or twice a year and so far its doing very nicely.