Twin I/O to Twin Outboard Conversion Project

[tpenfield]

Thanks for the picture edit . . .

It looks like I can accommodate a 2-bolt-hole upward adjustment, which would be 1.5". The Honda has 6 bolt hole positions and the re-power shop drilled the transom as such that the engine could go up 2 positions or down 1 position. I think he had a feeling that the engine was going to go up, not down .

Beyond that amount, it would be a jack plate or possibly vertical support brackets to get the engine higher, yet still have a good grip on the transom.

I'll be able to take a few more pictures over the next couple of days as the sea conditions are supposed to be calm.

 

[BMcF]

Thanks for the picture edit . . .

It looks like I can accommodate a 2-bolt-hole upward adjustment, which would be 1.5". The Honda has 6 bolt hole positions and the re-power shop drilled the transom as such that the engine could go up 2 positions or down 1 position. I think he had a feeling that the engine was going to go up, not down .

That is exactly how we've always designed and built our transom brackets. Not one has been "off" to the extent that raising the motor one or two bolts was not successful. One caveat: a couple that were lifted to the point of optimum trim/speed performance did experience significant prop slip/washout in hard turns and were subsequently lowered one hole. Compromises...they are everywhere

 

[tpenfield]

FWIW - I am seeing more and more outboard brackets done as hull extensions. It might be a trend

 

[tpenfield]

That is exactly how we've always designed and built our transom brackets. Not one has been "off" to the extent that raising the motor one or two bolts was not successful. One caveat: a couple that were lifted to the point of optimum trim/speed performance did experience significant prop slip/washout in hard turns and were subsequently lowered one hole. Compromises...they are everywhere

I was pretty much on a schedule crunch getting the boat ready for the season, so I did not put too much effort into measuring the engine height. The best I could tell was that the engines (Ventilation plates) would be about 1" higher than the planing surface, (the re-power shop confirmed that number).

The boat will need to come out of the water for its 20-hour service soon, and that will be an opportunity to check & adjust the engine height. I've already taken a look at what raising the engine by 2 holes (1.5") will look like. I'm thinking a third bolt on the top portion of the mount along with a support plate will be advisable.
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If it had to go any higher, it would probably need vertical support brackets.

 

[tpenfield]

Quick Update . . .

As the engines become more 'broken-in' I am seeing a sweet spot for fuel consumption. 3600 RPM, 31 mph, 1.4 mpg This is about 10% better than what I was seeing with the Mercruisers.

I've got about 14 hours on the engines and will probably pull the boat in Mid-September for its 20 hour service and raising of the engines ( 2 bolt holes = 1.5"). Not sure if I will have time to put the boat back in, as the Fall months are looking busy for other stuff. So, it looks like I'll be doing more performance testing next season.

 

[comfisherman]

Glad you were able to get some hrs on it. That was quite the undertaking as far as peojects go. Seems like reasonable mpg for the size of the boat and 700hp strapped to the back.

 

[tpenfield]

I've been meaning to post some video of the boat running out on the bay. So, here is a recent sample. . .

 

[tpenfield]

The boat is out of the water for it's break-in servicing. Oil/lube and will raise the engine height.

 

[tpenfield]

Pretty much done for the season . . .

The engine servicing ( i.e. 20-hour oil & lube change) was pretty straight forward . . . easier than the previous sterndrives.
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I pumped out 48 gallons of gasoline in 5 gallon increments and 'tested' the fuel sender/gauge as I went. The sender is a KUS/WEMA reed-switch type. It had some bad resistance readings in the 80% and 25% full range. This was most likely the cause of the erratic fuel level readings that I was seeing. So, I bought a new sender and tested it on the ohm-meter. This one was highly consistent. So, hopefully, next season I'll see more accurate fuel levels on the gauge.

I also did some trial/error with the NMEA2K network connections, as my GPS needed to be connected to the network in order for the auto-pilot to work. I got the GPS connected, so now the Optimus and the Garmin are talking to each other and the 3 auto-pilot icons (Track, Heading, Route) are showing up on the Garmin.
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I plan on raising the engines during the pre-season prep-work (May-June 2027), so I'll be able to do some more performance testing/tuning next season.

 

[fallguy]

I gave up on analog/resistance senders and installed Maretron lidar.

There is a new product made in Slovenia that is n2k stick on lidar for plastic tanks.

I hated the install of the Maretron focus tubes; it was an absolute nightmare and the reason is poor engineering done for low cost machining. But the system seems to be working well after I removed the dead band risers. If the tanks are ever super full, I don’t care if the reading is off. I could not reach the sender bolts and tighten them in my situation.

 

[fallguy]

If you buy the dead band riser Maretron tubes; get them machined so you have access to the lower bolt holes and so they are independent. It is impossible to get them sealed if there are access limits and the result is fuel vapors in the locker. Super dangerous and I dealt with it for 33 days at sea.

 

[tpenfield]

Thanks for the info on the Maretron senders. I got my new KUS reed switch sender in the tank for now.