Repowering- Questions

[islandfellow]

Hi all,

I posted this in the prop section, but think it may be better here. Any tips are greatly appreciated.

We have located a possible replacement engine for our Gulf Island 29. Originally there was Ferymann A-30 with 2.10:1 gear installed. The previous owner pulled it out on its last legs, claiming it was very underpowered.

The boat is fitted with a campbell 3 blade 13" - 12 prop.

The motor we have our eye on is a Yanmar 3HM35. I realize this is pushing the limits in terms of size for the boat ( it will fit). Do people think it is far too big? I have seen a few other gulf island 29's with 20-30 hp's. I have also seen an Alberg 30( which is almost the identical boat) with this exact motor. The gear is 2.14 :1.

Unfortunately, the 13" prop appears to be about the maximum diameter for the aperture.

What are peoples thoughts?

[speedoo]

What is the displacement?. Have you considered modifying the aperture so a larger prop will work?

[Astral Blue]

Originally Posted by islandfellow

Hi all,

I posted this in the prop section, but think it may be better here. Any tips are greatly appreciated.

We have located a possible replacement engine for our Gulf Island 29. Originally there was Ferymann A-30 with 2.10:1 gear installed. The previous owner pulled it out on its last legs, claiming it was very underpowered.

The boat is fitted with a campbell 3 blade 13" - 12 prop.

The motor we have our eye on is a Yanmar 3HM35. I realize this is pushing the limits in terms of size for the boat ( it will fit). Do people think it is far too big? I have seen a few other gulf island 29's with 20-30 hp's. I have also seen an Alberg 30( which is almost the identical boat) with this exact motor. The gear is 2.14 :1.

Unfortunately, the 13" prop appears to be about the maximum diameter for the aperture.

What are peoples thoughts?

On the surface the easy answer is the engine offers more horsepower than what is needed to propel the hull at hull speed on a Gulf Island 29. However, there are advantages associated with having more horsepower than you need.

1. If you are going against a strong current, the extra horsepower will compensate for it.
2. You can connect a high capacity alternator (200+ amp are available) and recharge your battery bank quickly as you are cruising under power.
3. The engine will work less harder to take your boat at hull speed than an engine with less horsepower. If the engine is working at 50 percent of its capacity versus 70 percent, it will have a longer life.

Just my two cents.