Tweet
Good morning,
I swapped my honda BF75/90(it had 90 carbs and jetting) to a DF115 of the same era on my 2001 Leader 180 single engine catamaran. This is the same hull as the Nautico and Seagull 18'. It is also the Seacat 18' and the Catcraft 18'. The old honda was a 20" shaft. The suzuki is a 25" shaft. I mounted it on a thmarine/CMC static 5 inch jack plate (https://thmarinesupplies.com/product...ical-extension). I adjusted the engine height to be about the same as where the honda was to the best of my ability. It's all the way down on the extension bracket. There is a built in negative degree tuck to the transom.
The honda engine had a 4 blade solas amita aluminum prop: 4 x 13.4 x 15. The boat had great grip, minimal ventilation and felt in control but it was slow only hitting 5500 RPM and 30 mph when really light.. Here's the performance of both engines:
engine ratio pitch rpm mph slip prop size engine weight
bf75A 2.33 15 5200 26 17.98% 4x13.4x15 384 lbs
df115 2.59 20 4000 23 17.23% 3x14x19 427 lbs
(DF115 is not max RPM, but this is cruise. After about 26 mph the boat feels to light and has some bow steer in its current state)
The Suzuki has a very new 3x14x19 Suzuki SS prop. The dealer said it was watergrip but I don't understand that they make that size in watergrip. The prop and boat has just as good or better acceleration and hook up but there are more noticeable slipping sounds. I also no longer have any ability to trim up. It feels like their is signficantly more stern lift than before and that the boat is riding bow down. If I attempt to trim the boat up, there is ventilation and the boat slows down. I haven't changed the geometry tremendously so I assumed I would still have trim control. When i look back the ventilation plate seems to be barely visible and similar to my other boats and the previous engine. I slightly remember my honda 75 had poor performance before putting on a 4 blade but in that case, I felt the additional stern lift of the 4 blade helped out. It basically did not vent with that motor. With the suzuki, I feel like the stern is too lifted - but maybe its just because i have no trim. When i accelerate above 26 mph the boat feels like the bow is steering it to one side or another as it hits waves - it didn't do this before. On slick water the bow will slowly move up and down. I've taken it to mid 30s and the boat felt it was going to spin or turn on me too quickly so i backed down. I've done that a few times with similar result. I'm OK running 26ish mph in this boat but I wanted to hit max RPM to make sure i was propped pitch correctly. I don't feel its safe to do that. The old engine didn't go fast enough to tell if the hull just hates speed or if its part of my set up.
I have a set of smart trim tabs in the garage - i thought this would help keep the boat level and not lean side to side. This is the 1 year they put a fuel tank on the starboard side and not the port so weight placement is something I have to think about when heading out. I generally throw the cooler on the port.
I have a permatrim that fits the suzuki in my garage. I'm leaning towards installing this but wanted to run the set up with out. I've put permatrims on 2 twin engine catamarans so far and saw success. They were not necessary on my larger seagull 270 though.
So my question: do I install the trim tabs and permatrims and see if that helps with the ventilation or do I first look at a 4 blade prop? I still have the 4x13.4x15 prop i can test with but the pitch would be extremely low - do i test it anyways? Am I missing an alternative. I can't lower the engine anymore and I don't believe I'd want to. I can raise it back up a hole or two but all the way down was superior to all the way up.
Thanks!
I swapped my honda BF75/90(it had 90 carbs and jetting) to a DF115 of the same era on my 2001 Leader 180 single engine catamaran. This is the same hull as the Nautico and Seagull 18'. It is also the Seacat 18' and the Catcraft 18'. The old honda was a 20" shaft. The suzuki is a 25" shaft. I mounted it on a thmarine/CMC static 5 inch jack plate (https://thmarinesupplies.com/product...ical-extension). I adjusted the engine height to be about the same as where the honda was to the best of my ability. It's all the way down on the extension bracket. There is a built in negative degree tuck to the transom.
The honda engine had a 4 blade solas amita aluminum prop: 4 x 13.4 x 15. The boat had great grip, minimal ventilation and felt in control but it was slow only hitting 5500 RPM and 30 mph when really light.. Here's the performance of both engines:
engine ratio pitch rpm mph slip prop size engine weight
bf75A 2.33 15 5200 26 17.98% 4x13.4x15 384 lbs
df115 2.59 20 4000 23 17.23% 3x14x19 427 lbs
(DF115 is not max RPM, but this is cruise. After about 26 mph the boat feels to light and has some bow steer in its current state)
The Suzuki has a very new 3x14x19 Suzuki SS prop. The dealer said it was watergrip but I don't understand that they make that size in watergrip. The prop and boat has just as good or better acceleration and hook up but there are more noticeable slipping sounds. I also no longer have any ability to trim up. It feels like their is signficantly more stern lift than before and that the boat is riding bow down. If I attempt to trim the boat up, there is ventilation and the boat slows down. I haven't changed the geometry tremendously so I assumed I would still have trim control. When i look back the ventilation plate seems to be barely visible and similar to my other boats and the previous engine. I slightly remember my honda 75 had poor performance before putting on a 4 blade but in that case, I felt the additional stern lift of the 4 blade helped out. It basically did not vent with that motor. With the suzuki, I feel like the stern is too lifted - but maybe its just because i have no trim. When i accelerate above 26 mph the boat feels like the bow is steering it to one side or another as it hits waves - it didn't do this before. On slick water the bow will slowly move up and down. I've taken it to mid 30s and the boat felt it was going to spin or turn on me too quickly so i backed down. I've done that a few times with similar result. I'm OK running 26ish mph in this boat but I wanted to hit max RPM to make sure i was propped pitch correctly. I don't feel its safe to do that. The old engine didn't go fast enough to tell if the hull just hates speed or if its part of my set up.
I have a set of smart trim tabs in the garage - i thought this would help keep the boat level and not lean side to side. This is the 1 year they put a fuel tank on the starboard side and not the port so weight placement is something I have to think about when heading out. I generally throw the cooler on the port.
I have a permatrim that fits the suzuki in my garage. I'm leaning towards installing this but wanted to run the set up with out. I've put permatrims on 2 twin engine catamarans so far and saw success. They were not necessary on my larger seagull 270 though.
So my question: do I install the trim tabs and permatrims and see if that helps with the ventilation or do I first look at a 4 blade prop? I still have the 4x13.4x15 prop i can test with but the pitch would be extremely low - do i test it anyways? Am I missing an alternative. I can't lower the engine anymore and I don't believe I'd want to. I can raise it back up a hole or two but all the way down was superior to all the way up.
Thanks!
Attached Files
Comment