Questions on re-powering from 9.8 to 9.9 or 15hp

I have a 36ft sailing catamaran. She is powered by two 9.8 tohatsu EPUL's. I am in the process of making some changes to the boat that will make her heavier a bit, and more windage... meaning I could use a bit more power. The 9,8's are just adequate now, but the advantage is they are lightweight and economical. I'd feel better with some extra power. So, my question is what should I move up to? I understand 9.9's are at the same block as 15's but with a different carb. is that true? The thing is I really need that extra long 25" shaft- AND it has to be electric start w/ remote. Should I shop for a 15 with XLS? OK to put a four bladed prop on that? or should i buy a 9.9 and convert the carb? Thanks.

Not sure about carb. change, but changing to a 4 blade prop will change your wide open throttle numbers

You did not mention whether your current motors are 2 or 4 stroke. In the US today, you can get the 9.9/15/20E, which is EFI. The 3 models use different ECUs. Yes, a 4-blade HT prop is available for these. The 9.9 is available in UL shaft, model would be MFS9.9EEPTUL, which will also have power tilt. If you end up needing more thrust, it's possible to change the ECU.

From a Tohatsu page on the new 9.9..."We set out to completely redesign an already top performing motor, and well exceeded that goal.
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They are reporting 50% better fuel efficiency in these! Sounds great, but the above quote makes me nervous- kinda like the "new coke" lol. Anyone have any direct experience with these?

I wonder if I would notice any appreciable difference in thrust with this new one straight out of the box from the (four stroke) 9.8's? Also don't need power tilt, in my case. May not be an option.

Thanks for the replies

The MFS 9.9/15/20 E is a redesign of the 15/20. The 9.9 is detuned via the ECU. In Ultra Long Remote, they are power tilt. However, you could buy the tiller version, and an RC conversion kit, and that would give you ultra long remote without PT. If you want more thrust, you could buy the bigger ECU later on. This is the same technology that has been used on the 40/50 for several years, and on the 25/30 for about a decade. Nothing really new, except setup on the smaller motors.

I have been selling these since last year, and all I can say is WOW, they are great. Start well, idle well, get great economy, and with EFI, the plugs last a long time. Has onboard water separator with float ring, oil filter (which the 9.8 lacks) and just flat out runs well. 5 year warranty in the US. I would be more than happy to sell you a pair.

Thanks for that reply Paul. Sounds like a good plan. Assume that the cost for the pt version would beat the cost and aggravation of the conversion kit, so I would have to decide if the weight penalty of the pt would be worth the savings. I have to hoist these things up and down a sliding bracket arrangement so every ounce counts. The wiring harness from the old remotes on the 9.8 would be compatable?

spritofstsimons, bring some else along to pull engines up, son ,grandson

The RC boxes themselves are the same setup, but the wiring harness for the old 9.8 was with discrete wires at the motor; the newer ones have a single connector at the motor. You could modify wiring, or just get a newer cord. Depends on how hard it is to route the cord to the controls.

Thanks again Paul, This may not be the proper place to discuss prices, and if so please direct me to another avenue, ie private e-mail or something. What I think I would like, (and up front I am not prepared to make this purchase yet- it would be next year at earliest), is a pair of 9.9's with 25"shafts four bladed props and with the carbs already converted to 15hp, and with the remote conversions already installed, and with a new electric cable. Unless it would make any more sense to just buy a pre- wired motor and remove the power tilt unit to save the weight? i Still have my old control boxes and shifter cables. They would have to be shipped to Georgia, US. 31522 Thanks.

Drop me an email: p.van.v at verizon dot net and we can discuss this. You will need to get the 9.9 to get the UL shaft. We'll get the tiller version to skip the power tilt, and add the RC kit. Then the bigger ECU (15 or 20 hp computer), and we will get the HT 4-blade props. Depending on the version of 9.8 you have, we will just get a new cord from the RC box to the motor; that will connect you properly. Depending on your skill level, you can install the RC kit, or we can do that. Freight costs will be the determining factor, because if I do all the setup, then I will need to re-ship to Georgia.

Thanks! I will e-mail when I get closer to being ready to make the move.

One last question: Would making the conversion to 15 or even 20 hp cause any early wear on the motors? Would all warranties still apply?

Of course, the harder you run, the more wear. But considering that I have never seen one worn out, I don't see an issue. Most issues have been due to neglect or abuse. Don't forget that these are sold as 9.9, 15, and 20s, The smaller ones are detuned to match USCG placards. Yes, they would still be under warranty.